Add RESPECT/IGNORE NULLS and FROM FIRST/LAST options

From b4170a6970655254e36aed7ce22b709ff63dcfac Mon Sep 17 00:00:00 2001
From: David Fetter <david@fetter.org>
Date: Sun, 15 Jul 2018 23:04:34 -0700
Subject: [PATCH] RESPECT/IGNORE NULLS, FIRST, LAST in windowing functions
 v0002
To: pgsql-hackers@postgresql.org

---
 doc/src/sgml/func.sgml                    |  43 +--
 src/backend/catalog/sql_features.txt      |   4 +-
 src/backend/parser/gram.y                 | 190 ++++++++++-
 src/backend/utils/adt/ruleutils.c         |  45 ++-
 src/backend/utils/adt/windowfuncs.c       | 278 +++++++++++++++-
 src/include/catalog/pg_proc.dat           |  40 +++
 src/include/catalog/pg_type.dat           |  10 +
 src/include/nodes/parsenodes.h            |   6 +
 src/include/parser/kwlist.h               |   7 +
 src/test/regress/expected/oidjoins.out    |  32 ++
 src/test/regress/expected/type_sanity.out |  44 ++-
 src/test/regress/expected/window.out      | 366 ++++++++++++++++++++++
 src/test/regress/sql/oidjoins.sql         |  16 +
 src/test/regress/sql/window.sql           |  63 ++++
 14 files changed, 1085 insertions(+), 59 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index edc9be92a6..cf44aeddcf 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -14762,7 +14762,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <function>
          lag(<replaceable class="parameter">value</replaceable> <type>anyelement</type>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</type>
-             [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]])
+             [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]]) [null_treatment]
        </function>
       </entry>
       <entry>
@@ -14791,7 +14791,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <function>
          lead(<replaceable class="parameter">value</replaceable> <type>anyelement</type>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</type>
-              [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]])
+              [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]]) [null_treatment]
        </function>
       </entry>
       <entry>
@@ -14817,7 +14817,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <indexterm>
         <primary>first_value</primary>
        </indexterm>
-       <function>first_value(<replaceable class="parameter">value</replaceable> <type>any</type>)</function>
+       <function>first_value(<replaceable class="parameter">value</replaceable> <type>any</type>) [null_treatment]</function>
       </entry>
       <entry>
        <type>same type as <replaceable class="parameter">value</replaceable></type>
@@ -14833,7 +14833,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <indexterm>
         <primary>last_value</primary>
        </indexterm>
-       <function>last_value(<replaceable class="parameter">value</replaceable> <type>any</type>)</function>
+       <function>last_value(<replaceable class="parameter">value</replaceable> <type>any</type>) [null_treatment]</function>
       </entry>
       <entry>
        <type>same type as <replaceable class="parameter">value</replaceable></type>
@@ -14850,7 +14850,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <primary>nth_value</primary>
        </indexterm>
        <function>
-         nth_value(<replaceable class="parameter">value</replaceable> <type>any</type>, <replaceable class="parameter">nth</replaceable> <type>integer</type>)
+         nth_value(<replaceable class="parameter">value</replaceable> <type>any</type>, <replaceable class="parameter">nth</replaceable> <type>integer</type>) [from_first_last] [null_treatment]
        </function>
       </entry>
       <entry>
@@ -14865,6 +14865,23 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
     </tbody>
    </tgroup>
   </table>
+  
+  <para>
+  In <xref linkend="functions-window-table"/>, <replaceable>null_treatment</replaceable> is one of:
+  <synopsis>
+    RESPECT NULLS
+    IGNORE NULLS
+  </synopsis>
+
+  and <replaceable>from_first_last</replaceable> is one of:
+  <synopsis>
+    FROM FIRST
+    FROM LAST
+  </synopsis>
+  <literal>RESPECT NULLS</literal> specifies the default behavior to include nulls in the result.
+  <literal>IGNORE NULLS</literal> ignores any null values when determining a result.
+  <literal>FROM FIRST</literal> specifies the default ordering, and <literal>FROM LAST</literal> reverses the ordering.
+  </para>
 
   <para>
    All of the functions listed in
@@ -14901,22 +14918,6 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
    Other frame specifications can be used to obtain other effects.
   </para>
 
-  <note>
-   <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
-    ordering.)
-   </para>
-  </note>
-
   <para>
    <function>cume_dist</function> computes the fraction of partition rows that
    are less than or equal to the current row and its peers, while
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index aeb262a5b0..30257157b8 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -494,9 +494,9 @@ T612	Advanced OLAP operations			NO	some forms supported
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE function			YES	
-T618	NTH_VALUE function			NO	function exists, but some options missing
+T618	NTH_VALUE function			YES	
 T619	Nested window functions			NO	
 T620	WINDOW clause: GROUPS option			YES	
 T621	Enhanced numeric functions			YES	
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 87f5e95827..27ea969952 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -153,6 +153,7 @@ static Node *makeBitStringConst(char *str, int location);
 static Node *makeNullAConst(int location);
 static Node *makeAConst(Value *v, int location);
 static Node *makeBoolAConst(bool state, int location);
+static Node *makeTypedBoolAConst(bool state, char *type, int location);
 static RoleSpec *makeRoleSpec(RoleSpecType type, int location);
 static void check_qualified_name(List *names, core_yyscan_t yyscanner);
 static List *check_func_name(List *names, core_yyscan_t yyscanner);
@@ -561,7 +562,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	xml_namespace_list
 %type <target>	xml_namespace_el
 
-%type <node>	func_application func_expr_common_subexpr
+%type <node>	func_application func_expr_common_subexpr func_expr_first_last
 %type <node>	func_expr func_expr_windowless
 %type <node>	common_table_expr
 %type <with>	with_clause opt_with_clause
@@ -569,6 +570,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 %type <list>	within_group_clause
 %type <node>	filter_clause
+%type <ival>	from_first_last_null_treatment_clause null_treatment_clause
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
@@ -632,14 +634,14 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN
 	EXTENSION EXTERNAL EXTRACT
 
-	FALSE_P FAMILY FETCH FILTER FIRST_P FLOAT_P FOLLOWING FOR
+	FALSE_P FAMILY FETCH FILTER FIRST_P FIRST_VALUE FLOAT_P FOLLOWING FOR
 	FORCE FOREIGN FORWARD FREEZE FROM FULL FUNCTION FUNCTIONS
 
 	GENERATED GLOBAL GRANT GRANTED GREATEST GROUP_P GROUPING GROUPS
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -648,14 +650,14 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	KEY
 
-	LABEL LANGUAGE LARGE_P LAST_P LATERAL_P
-	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
+	LABEL LAG LANGUAGE LARGE_P LAST_P LAST_VALUE LATERAL_P
+	LEAD LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
 	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEW NEXT NO NONE
-	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
+	NOT NOTHING NOTIFY NOTNULL NOWAIT NTH_VALUE NULL_P NULLIF
 	NULLS_P NUMERIC
 
 	OBJECT_P OF OFF OFFSET OIDS OLD ON ONLY OPERATOR OPTION OPTIONS OR
@@ -670,7 +672,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -714,6 +716,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 /* Precedence: lowest to highest */
 %nonassoc	SET				/* see relation_expr_opt_alias */
+%nonassoc	FIRST_VALUE LAG LAST_VALUE LEAD NTH_VALUE
 %left		UNION EXCEPT
 %left		INTERSECT
 %left		OR
@@ -763,6 +766,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %right		UMINUS
 %left		'[' ']'
 %left		'(' ')'
+%left		FROM FIRST_P LAST_P NULLS_P
 %left		TYPECAST
 %left		'.'
 /*
@@ -13638,6 +13642,33 @@ func_application: func_name '(' ')'
 				}
 		;
 
+null_treatment_clause:
+			RESPECT NULLS_P				{ $$ = 0; }
+			| IGNORE_P NULLS_P			{ $$ = WINFUNC_OPT_IGNORE_NULLS; }
+		;
+
+from_first_last_null_treatment_clause:
+		FROM FIRST_P null_treatment_clause
+				{
+					$$ = $3;
+				}
+		| FROM LAST_P null_treatment_clause
+				{
+					$$ = WINFUNC_OPT_FROM_LAST | $3;
+				}
+		| null_treatment_clause
+				{
+					$$ = $1;
+				}
+		| FROM FIRST_P
+				{
+					$$ = 0;
+				}
+		| FROM LAST_P
+				{
+					$$ = WINFUNC_OPT_FROM_LAST;
+				}
+		;
 
 /*
  * func_expr and its cousin func_expr_windowless are split out from c_expr just
@@ -13685,6 +13716,133 @@ func_expr: func_application within_group_clause filter_clause over_clause
 				}
 			| func_expr_common_subexpr
 				{ $$ = $1; }
+			| func_expr_first_last over_clause
+				{
+					FuncCall *n = (FuncCall *) $1;
+					n->over = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+func_expr_first_last:
+			FIRST_VALUE '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("first_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			|
+			FIRST_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("first_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAG '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("lag")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAG '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("lag")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAST_VALUE '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("last_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAST_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("last_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LEAD '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("lead")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LEAD '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("lead")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| NTH_VALUE '(' func_arg_list opt_sort_clause ')' from_first_last_null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Nulls and From First options to bools */
+					if (winFuncArgs & WINFUNC_OPT_FROM_LAST)
+						l = lappend(l, makeTypedBoolAConst(true, "fromlast", @2));
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("nth_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| NTH_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("nth_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
 		;
 
 /*
@@ -15088,6 +15246,7 @@ unreserved_keyword:
 			| FAMILY
 			| FILTER
 			| FIRST_P
+			| FIRST_VALUE
 			| FOLLOWING
 			| FORCE
 			| FORWARD
@@ -15103,6 +15262,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -15123,9 +15283,12 @@ unreserved_keyword:
 			| ISOLATION
 			| KEY
 			| LABEL
+			| LAG
 			| LANGUAGE
 			| LARGE_P
 			| LAST_P
+			| LAST_VALUE
+			| LEAD
 			| LEAKPROOF
 			| LEVEL
 			| LISTEN
@@ -15153,6 +15316,7 @@ unreserved_keyword:
 			| NOTHING
 			| NOTIFY
 			| NOWAIT
+			| NTH_VALUE
 			| NULLS_P
 			| OBJECT_P
 			| OF
@@ -15204,6 +15368,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
@@ -15675,6 +15840,15 @@ makeAConst(Value *v, int location)
  */
 static Node *
 makeBoolAConst(bool state, int location)
+{
+	return makeTypedBoolAConst(state, "bool", location);
+}
+
+/* makeTypedBoolAConst()
+ * Create an A_Const string node from a boolean and store inside the specified type.
+ */
+static Node *
+makeTypedBoolAConst(bool state, char *type, int location)
 {
 	A_Const *n = makeNode(A_Const);
 
@@ -15682,7 +15856,7 @@ makeBoolAConst(bool state, int location)
 	n->val.val.str = (state ? "t" : "f");
 	n->location = location;
 
-	return makeTypeCast((Node *)n, SystemTypeName("bool"), -1);
+	return makeTypeCast((Node *)n, SystemTypeName(type), -1);
 }
 
 /* makeRoleSpec
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index a38aed2065..1d6ba490c0 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9235,6 +9235,8 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 	int			nargs;
 	List	   *argnames;
 	ListCell   *l;
+	bool		ignorenulls = false,
+				fromlast = false;
 
 	if (list_length(wfunc->args) > FUNC_MAX_ARGS)
 		ereport(ERROR,
@@ -9261,15 +9263,47 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 	if (wfunc->winstar)
 		appendStringInfoChar(buf, '*');
 	else
-		get_rule_expr((Node *) wfunc->args, context, true);
+	{
+		ListCell	*arglist;
+		Node *argnode = (Node *) wfunc->args;
+
+		get_rule_expr(argnode, context, true);
+
+		/* Determine if FROM LAST and/or IGNORE NULLS should be appended */
+		foreach(arglist, (List *) argnode)
+		{
+			Node *arg = (Node *) lfirst(arglist);
+			if (nodeTag(arg) == T_Const)
+			{
+				Const *constnode = (Const *) arg;
+				if (constnode->consttype == FROMLASTOID)
+				{
+					/* parser does not save FROM FIRST arguments */
+					fromlast = true;
+					buf->len -= 2;
+				}
+				if (constnode->consttype == IGNORENULLSOID)
+				{
+					/* parser does not save RESPECT NULLS arguments */
+					ignorenulls = true;
+					buf->len -= 2;
+				}
+			}
+		}
+	}
+
+	appendStringInfoChar(buf, ')');
+	if (fromlast)
+		appendStringInfoString(buf, " FROM LAST");
+	if (ignorenulls)
+		appendStringInfoString(buf, " IGNORE NULLS");
 
 	if (wfunc->aggfilter != NULL)
 	{
 		appendStringInfoString(buf, ") FILTER (WHERE ");
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
-
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, " OVER ");
 
 	foreach(l, context->windowClause)
 	{
@@ -9444,6 +9478,11 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
 				appendStringInfoString(buf, "false");
 			break;
 
+		case FROMLASTOID:
+		case IGNORENULLSOID:
+			showtype = -1;
+			break;
+
 		default:
 			simple_quote_literal(buf, extval);
 			break;
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 40ba783572..094590334d 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -38,7 +38,14 @@ typedef struct
 static bool rank_up(WindowObject winobj);
 static Datum leadlag_common(FunctionCallInfo fcinfo,
 			   bool forward, bool withoffset, bool withdefault);
-
+static Datum leadlag_common_ignore_nulls(FunctionCallInfo fcinfo,
+			   bool forward, bool withoffset, bool withdefault);
+static Datum
+window_nth_value_ignorenulls_common(FunctionCallInfo fcinfo, int32 nth,
+									bool fromlast);
+static Datum
+window_nth_value_respectnulls_common(FunctionCallInfo fcinfo, int32 nth,
+									bool fromlast);
 
 /*
  * utility routine for *_rank functions.
@@ -328,6 +335,79 @@ leadlag_common(FunctionCallInfo fcinfo,
 	PG_RETURN_DATUM(result);
 }
 
+static Datum
+leadlag_common_ignore_nulls(FunctionCallInfo fcinfo,
+			   bool forward, bool withoffset, bool withdefault)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	int32		offset;
+	Datum		result;
+	bool		isnull;
+	bool		isout = false;
+	int32		notnull_offset = 0, tmp_offset = 0;
+
+	if (withoffset)
+	{
+		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+		if (isnull)
+			PG_RETURN_NULL();
+		if (offset < 0)
+		{
+			offset = abs(offset);
+			forward = !forward;
+		} else if (offset == 0)
+		{
+			result = WinGetFuncArgInPartition(winobj, 0, 0,
+											  WINDOW_SEEK_CURRENT,
+											  false,
+											  &isnull, &isout);
+			if (isnull || isout)
+				PG_RETURN_NULL();
+			else
+				PG_RETURN_DATUM(result);
+		}
+	}
+	else
+		offset = 1;
+
+	while (notnull_offset < offset)
+	{
+		tmp_offset++;
+		result = WinGetFuncArgInPartition(winobj, 0,
+									  (forward ? tmp_offset : -tmp_offset),
+									  WINDOW_SEEK_CURRENT,
+									  false,
+									  &isnull, &isout);
+		if (isout)
+			goto out_of_frame;
+		else if (!isnull)
+			notnull_offset++;
+	}
+
+	result = WinGetFuncArgInPartition(winobj, 0,
+									  (forward ? tmp_offset : -tmp_offset),
+									  WINDOW_SEEK_CURRENT,
+									  false,
+									  &isnull, &isout);
+	if (isout)
+		goto out_of_frame;
+	else
+		PG_RETURN_DATUM(result);
+
+	out_of_frame:
+	/*
+	* target row is out of the partition; supply default value if
+	* provided. Otherwise return NULL.
+	*/
+	if (withdefault)
+	{
+		result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		PG_RETURN_DATUM(result);
+	}
+	else
+		PG_RETURN_NULL();
+}
+
 /*
  * lag
  * returns the value of VE evaluated on a row that is 1
@@ -363,6 +443,24 @@ window_lag_with_offset_and_default(PG_FUNCTION_ARGS)
 	return leadlag_common(fcinfo, false, true, true);
 }
 
+Datum
+window_lag_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, false, false);
+}
+
+Datum
+window_lag_with_offset_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, true, false);
+}
+
+Datum
+window_lag_with_offset_and_default_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, true, true);
+}
+
 /*
  * lead
  * returns the value of VE evaluated on a row that is 1
@@ -398,6 +496,24 @@ window_lead_with_offset_and_default(PG_FUNCTION_ARGS)
 	return leadlag_common(fcinfo, true, true, true);
 }
 
+Datum
+window_lead_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, false, false);
+}
+
+Datum
+window_lead_with_offset_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, true, false);
+}
+
+Datum
+window_lead_with_offset_and_default_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, true, true);
+}
+
 /*
  * first_value
  * return the value of VE evaluated on the first row of the
@@ -419,6 +535,31 @@ window_first_value(PG_FUNCTION_ARGS)
 	PG_RETURN_DATUM(result);
 }
 
+Datum
+window_first_value_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	int64		pos;
+
+	isout = false;
+	pos = 0;
+
+	while (!isout)
+	{
+		result = WinGetFuncArgInFrame(winobj, 0,
+								  pos, WINDOW_SEEK_HEAD, false,
+								  &isnull, &isout);
+		if (!isnull)
+			PG_RETURN_DATUM(result);
+		pos++;
+	}
+
+	PG_RETURN_NULL();
+}
+
 /*
  * last_value
  * return the value of VE evaluated on the last row of the
@@ -440,35 +581,156 @@ window_last_value(PG_FUNCTION_ARGS)
 	PG_RETURN_DATUM(result);
 }
 
+Datum
+window_last_value_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	int64		pos;
+
+	isout = false;
+	pos = 0;
+
+	while (!isout)
+	{
+		result = WinGetFuncArgInFrame(winobj, 0,
+								  pos, WINDOW_SEEK_TAIL, false,
+								  &isnull, &isout);
+		if (!isnull)
+			PG_RETURN_DATUM(result);
+		pos--;
+	}
+
+	PG_RETURN_NULL();
+}
+
 /*
  * nth_value
  * return the value of VE evaluated on the n-th row from the first
  * row of the window frame, per spec.
  */
-Datum
-window_nth_value(PG_FUNCTION_ARGS)
+static Datum
+window_nth_value_respectnulls_common(FunctionCallInfo fcinfo, int32 nth,
+									bool fromlast)
 {
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	bool		const_offset;
 	Datum		result;
 	bool		isnull;
-	int32		nth;
+	const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
+
+	if (nth <= 0)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
+				 errmsg("argument of nth_value must be greater than zero")));
+
+	result = WinGetFuncArgInFrame(winobj,
+								   0,
+								  nth - 1,
+								  fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD, const_offset,
+								  &isnull,
+								  NULL);
+	if (isnull)
+		PG_RETURN_NULL();
+
+	PG_RETURN_DATUM(result);
+}
+
+static Datum
+window_nth_value_ignorenulls_common(FunctionCallInfo fcinfo, int32 nth,
+									bool fromlast)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	int32		tmp_offset, notnull_offset = 0;
 
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (fromlast)
+		tmp_offset = 1;
+	else
+		tmp_offset = -1;
+
 	if (isnull)
 		PG_RETURN_NULL();
-	const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
 
 	if (nth <= 0)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
 				 errmsg("argument of nth_value must be greater than zero")));
 
+	while (notnull_offset < nth)
+	{
+		fromlast ? tmp_offset-- : tmp_offset++;
+		result = WinGetFuncArgInFrame(winobj, 0,
+									  tmp_offset, fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD,
+									  false, &isnull, &isout);
+		if (isout)
+			PG_RETURN_NULL();
+		if (!isnull)
+			notnull_offset++;
+	}
+
 	result = WinGetFuncArgInFrame(winobj, 0,
-								  nth - 1, WINDOW_SEEK_HEAD, const_offset,
-								  &isnull, NULL);
-	if (isnull)
+								  tmp_offset, fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD,
+								  false, &isnull, &isout);
+	if (isout || isnull)
 		PG_RETURN_NULL();
 
 	PG_RETURN_DATUM(result);
 }
+
+Datum
+window_nth_value(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_respectnulls_common(fcinfo, nth, false));
+}
+
+Datum
+window_nth_value_with_first_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_respectnulls_common(fcinfo, nth, true));
+}
+
+Datum
+window_nth_value_with_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_ignorenulls_common(fcinfo, nth, false));
+}
+
+Datum
+window_nth_value_with_first_nulls_opts(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_ignorenulls_common(fcinfo, nth, true));
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index a14651010f..6800b4aecf 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9432,32 +9432,72 @@
 { oid => '3106', descr => 'fetch the preceding row value',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_lag' },
+{ oid => '4188', descr => 'fetch the preceding row value with nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_lag_nulls_opt' },
 { oid => '3107', descr => 'fetch the Nth preceding row value',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_lag_with_offset' },
+{ oid => '4189', descr => 'fetch the Nth preceding row value with nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_lag_with_offset_nulls_opt' },
 { oid => '3108', descr => 'fetch the Nth preceding row value with default',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4 anyelement',
   prosrc => 'window_lag_with_offset_and_default' },
+{ oid => '4190', descr => 'fetch the Nth preceding row value with default and nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 anyelement ignorenulls',
+  prosrc => 'window_lag_with_offset_and_default_nulls_opt' },
 { oid => '3109', descr => 'fetch the following row value',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_lead' },
+{ oid => '4191', descr => 'fetch the following row value with nulls option',
+  proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_lead_nulls_opt' },
 { oid => '3110', descr => 'fetch the Nth following row value',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_lead_with_offset' },
+{ oid => '4192', descr => 'fetch the Nth following row value with nulls option',
+  proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_lead_with_offset_nulls_opt' },
 { oid => '3111', descr => 'fetch the Nth following row value with default',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4 anyelement',
   prosrc => 'window_lead_with_offset_and_default' },
+{ oid => '4193', descr => 'fetch the Nth following row value with default and nulls option',
+  proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 anyelement ignorenulls',
+  prosrc => 'window_lead_with_offset_and_default_nulls_opt' },
 { oid => '3112', descr => 'fetch the first row value',
   proname => 'first_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_first_value' },
+{ oid => '4194', descr => 'fetch the first row value with nulls option',
+  proname => 'first_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_first_value_nulls_opt' },
 { oid => '3113', descr => 'fetch the last row value',
   proname => 'last_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_last_value' },
+{ oid => '4195', descr => 'fetch the last row value with nulls option',
+  proname => 'last_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_last_value_nulls_opt' },
 { oid => '3114', descr => 'fetch the Nth row value',
   proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_nth_value' },
+{ oid => '4196', descr => 'fetch the Nth row value with from first option',
+  proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 fromlast',
+  prosrc => 'window_nth_value_with_first_opt' },
+{ oid => '4197', descr => 'fetch the Nth row value with nulls option',
+  proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_nth_value_with_nulls_opt' },
+{ oid => '4198', descr => 'fetch the Nth row value with from first and nulls option',
+  proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 fromlast ignorenulls',
+  prosrc => 'window_nth_value_with_first_nulls_opts' },
 
 # functions for range types
 { oid => '3832', descr => 'I/O',
diff --git a/src/include/catalog/pg_type.dat b/src/include/catalog/pg_type.dat
index 48e01cd694..72e59422d8 100644
--- a/src/include/catalog/pg_type.dat
+++ b/src/include/catalog/pg_type.dat
@@ -938,5 +938,15 @@
   typname => 'anyrange', typlen => '-1', typbyval => 'f', typtype => 'p',
   typcategory => 'P', typinput => 'anyrange_in', typoutput => 'anyrange_out',
   typreceive => '-', typsend => '-', typalign => 'd', typstorage => 'x' },
+{ oid => '4142',
+  typname => 'ignorenulls', descr => 'boolean wrapper, \'true\'/\'false\'',
+  typlen => '1', typbyval => 't', typtype => 'b', typcategory => 'B',
+  typinput => 'boolin', typoutput => 'boolout', typreceive => 'boolrecv',
+  typsend => 'boolsend', typalign => 'c' },
+{ oid => '4187',
+  typname => 'fromlast', descr => 'boolean wrapper, \'true\'/\'false\'',
+  typlen => '1', typbyval => 't', typtype => 'b', typcategory => 'B',
+  typinput => 'boolin', typoutput => 'boolout', typreceive => 'boolrecv',
+  typsend => 'boolsend', typalign => 'c' },
 
 ]
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 7855cff30d..393f530101 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -533,6 +533,12 @@ typedef struct WindowDef
 	(FRAMEOPTION_RANGE | FRAMEOPTION_START_UNBOUNDED_PRECEDING | \
 	 FRAMEOPTION_END_CURRENT_ROW)
 
+/*
+ * From Last and Null Treatment options
+ */
+#define WINFUNC_OPT_FROM_LAST			0x00001 /* FROM LAST */
+#define WINFUNC_OPT_IGNORE_NULLS		0x00002 /* IGNORE NULLS */
+
 /*
  * RangeSubselect - subquery appearing in a FROM clause
  */
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 23db40147b..a043742768 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -164,6 +164,7 @@ PG_KEYWORD("family", FAMILY, UNRESERVED_KEYWORD)
 PG_KEYWORD("fetch", FETCH, RESERVED_KEYWORD)
 PG_KEYWORD("filter", FILTER, UNRESERVED_KEYWORD)
 PG_KEYWORD("first", FIRST_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("first_value", FIRST_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("float", FLOAT_P, COL_NAME_KEYWORD)
 PG_KEYWORD("following", FOLLOWING, UNRESERVED_KEYWORD)
 PG_KEYWORD("for", FOR, RESERVED_KEYWORD)
@@ -190,6 +191,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -223,10 +225,13 @@ PG_KEYWORD("isolation", ISOLATION, UNRESERVED_KEYWORD)
 PG_KEYWORD("join", JOIN, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("key", KEY, UNRESERVED_KEYWORD)
 PG_KEYWORD("label", LABEL, UNRESERVED_KEYWORD)
+PG_KEYWORD("lag", LAG, UNRESERVED_KEYWORD)
 PG_KEYWORD("language", LANGUAGE, UNRESERVED_KEYWORD)
 PG_KEYWORD("large", LARGE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("last", LAST_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("last_value", LAST_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("lateral", LATERAL_P, RESERVED_KEYWORD)
+PG_KEYWORD("lead", LEAD, UNRESERVED_KEYWORD)
 PG_KEYWORD("leading", LEADING, RESERVED_KEYWORD)
 PG_KEYWORD("leakproof", LEAKPROOF, UNRESERVED_KEYWORD)
 PG_KEYWORD("least", LEAST, COL_NAME_KEYWORD)
@@ -267,6 +272,7 @@ PG_KEYWORD("nothing", NOTHING, UNRESERVED_KEYWORD)
 PG_KEYWORD("notify", NOTIFY, UNRESERVED_KEYWORD)
 PG_KEYWORD("notnull", NOTNULL, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("nowait", NOWAIT, UNRESERVED_KEYWORD)
+PG_KEYWORD("nth_value", NTH_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("null", NULL_P, RESERVED_KEYWORD)
 PG_KEYWORD("nullif", NULLIF, COL_NAME_KEYWORD)
 PG_KEYWORD("nulls", NULLS_P, UNRESERVED_KEYWORD)
@@ -336,6 +342,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
+PG_KEYWORD("respect", RESPECT, UNRESERVED_KEYWORD)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD)
 PG_KEYWORD("returning", RETURNING, RESERVED_KEYWORD)
diff --git a/src/test/regress/expected/oidjoins.out b/src/test/regress/expected/oidjoins.out
index ef268d348e..d75bdfcd7b 100644
--- a/src/test/regress/expected/oidjoins.out
+++ b/src/test/regress/expected/oidjoins.out
@@ -897,6 +897,22 @@ WHERE	seqtypid != 0 AND
 ------+----------
 (0 rows)
 
+SELECT	ctid, classid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	classid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_class pk WHERE pk.oid = fk.classid);
+ ctid | classid 
+------+---------
+(0 rows)
+
+SELECT	ctid, objid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	objid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_database pk WHERE pk.oid = fk.objid);
+ ctid | objid 
+------+-------
+(0 rows)
+
 SELECT	ctid, refclassid
 FROM	pg_catalog.pg_shdepend fk
 WHERE	refclassid != 0 AND
@@ -905,6 +921,22 @@ WHERE	refclassid != 0 AND
 ------+------------
 (0 rows)
 
+SELECT	ctid, refobjid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	refobjid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_authid pk WHERE pk.oid = fk.refobjid);
+ ctid | refobjid 
+------+----------
+(0 rows)
+
+SELECT	ctid, objoid
+FROM	pg_catalog.pg_shdescription fk
+WHERE	objoid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_database pk WHERE pk.oid = fk.objoid);
+ ctid | objoid 
+------+--------
+(0 rows)
+
 SELECT	ctid, classoid
 FROM	pg_catalog.pg_shdescription fk
 WHERE	classoid != 0 AND
diff --git a/src/test/regress/expected/type_sanity.out b/src/test/regress/expected/type_sanity.out
index b1419d4bc2..45bce0de58 100644
--- a/src/test/regress/expected/type_sanity.out
+++ b/src/test/regress/expected/type_sanity.out
@@ -73,7 +73,9 @@ WHERE p1.typtype not in ('c','d','p') AND p1.typname NOT LIKE E'\\_%'
  3361 | pg_ndistinct
  3402 | pg_dependencies
   210 | smgr
-(4 rows)
+ 4142 | ignorenulls
+ 4187 | fromlast
+(6 rows)
 
 -- Make sure typarray points to a varlena array type of our own base
 SELECT p1.oid, p1.typname as basetype, p2.typname as arraytype,
@@ -166,10 +168,12 @@ WHERE p1.typinput = p2.oid AND p1.typtype in ('b', 'p') AND NOT
     (p1.typelem != 0 AND p1.typlen < 0) AND NOT
     (p2.prorettype = p1.oid AND NOT p2.proretset)
 ORDER BY 1;
- oid  |  typname  | oid | proname 
-------+-----------+-----+---------
- 1790 | refcursor |  46 | textin
-(1 row)
+ oid  |   typname   | oid  | proname 
+------+-------------+------+---------
+ 1790 | refcursor   |   46 | textin
+ 4142 | ignorenulls | 1242 | boolin
+ 4187 | fromlast    | 1242 | boolin
+(3 rows)
 
 -- Varlena array types will point to array_in
 -- Exception as of 8.1: int2vector and oidvector have their own I/O routines
@@ -217,10 +221,12 @@ WHERE p1.typoutput = p2.oid AND p1.typtype in ('b', 'p') AND NOT
       (p2.oid = 'array_out'::regproc AND
        p1.typelem != 0 AND p1.typlen = -1)))
 ORDER BY 1;
- oid  |  typname  | oid | proname 
-------+-----------+-----+---------
- 1790 | refcursor |  47 | textout
-(1 row)
+ oid  |   typname   | oid  | proname 
+------+-------------+------+---------
+ 1790 | refcursor   |   47 | textout
+ 4142 | ignorenulls | 1243 | boolout
+ 4187 | fromlast    | 1243 | boolout
+(3 rows)
 
 SELECT p1.oid, p1.typname, p2.oid, p2.proname
 FROM pg_type AS p1, pg_proc AS p2
@@ -280,10 +286,12 @@ WHERE p1.typreceive = p2.oid AND p1.typtype in ('b', 'p') AND NOT
     (p1.typelem != 0 AND p1.typlen < 0) AND NOT
     (p2.prorettype = p1.oid AND NOT p2.proretset)
 ORDER BY 1;
- oid  |  typname  | oid  | proname  
-------+-----------+------+----------
- 1790 | refcursor | 2414 | textrecv
-(1 row)
+ oid  |   typname   | oid  | proname  
+------+-------------+------+----------
+ 1790 | refcursor   | 2414 | textrecv
+ 4142 | ignorenulls | 2436 | boolrecv
+ 4187 | fromlast    | 2436 | boolrecv
+(3 rows)
 
 -- Varlena array types will point to array_recv
 -- Exception as of 8.1: int2vector and oidvector have their own I/O routines
@@ -340,10 +348,12 @@ WHERE p1.typsend = p2.oid AND p1.typtype in ('b', 'p') AND NOT
       (p2.oid = 'array_send'::regproc AND
        p1.typelem != 0 AND p1.typlen = -1)))
 ORDER BY 1;
- oid  |  typname  | oid  | proname  
-------+-----------+------+----------
- 1790 | refcursor | 2415 | textsend
-(1 row)
+ oid  |   typname   | oid  | proname  
+------+-------------+------+----------
+ 1790 | refcursor   | 2415 | textsend
+ 4142 | ignorenulls | 2437 | boolsend
+ 4187 | fromlast    | 2437 | boolsend
+(3 rows)
 
 SELECT p1.oid, p1.typname, p2.oid, p2.proname
 FROM pg_type AS p1, pg_proc AS p2
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 562006a2b8..87b9340129 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -3787,3 +3787,369 @@ SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
  5 | t | t        | t
 (5 rows)
 
+-- FROM LAST and IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit int
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560);
+  -- test view definitions are preserved
+CREATE TEMP VIEW v_planets AS
+    SELECT
+      name,
+      sum(orbit) OVER (order by orbit) as sum_rows,
+      lag(orbit, 1) RESPECT NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+      lag(orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,
+      first_value(orbit) IGNORE NULLS OVER w AS first_value_ignore,
+      nth_value(orbit,2) FROM FIRST IGNORE NULLS OVER w AS nth_first_ignore,
+      nth_value(orbit,2) FROM LAST IGNORE NULLS OVER w AS nth_last_ignore
+    FROM planets
+    WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_planets');
+                                  pg_get_viewdef                                  
+----------------------------------------------------------------------------------
+  SELECT planets.name,                                                           +
+     sum(planets.orbit) OVER (ORDER BY planets.orbit) AS sum_rows,               +
+     lag(planets.orbit, 1) OVER (ORDER BY planets.name DESC) AS lagged_by_1,     +
+     lag(planets.orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,                   +
+     first_value(planets.orbit) IGNORE NULLS OVER w AS first_value_ignore,       +
+     nth_value(planets.orbit, 2) IGNORE NULLS OVER w AS nth_first_ignore,        +
+     nth_value(planets.orbit, 2) FROM LAST IGNORE NULLS OVER w AS nth_last_ignore+
+    FROM planets                                                                 +
+   WINDOW w AS (ORDER BY planets.name);
+(1 row)
+
+SELECT name, lag(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |      
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |      
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |  4332
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   | 24491
+(9 rows)
+
+SELECT name, lead(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |      
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |      
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |      
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |      
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |    88
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |   224
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |  4332
+ jupiter |    88
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |   224
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |  4332
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   | 24491
+(9 rows)
+
+SELECT name, first_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |            
+ jupiter |            
+ mars    |            
+ mercury |            
+ neptune |            
+ pluto   |            
+ saturn  |            
+ uranus  |            
+ venus   |            
+(9 rows)
+
+SELECT name, first_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |            
+ jupiter |            
+ mars    |            
+ mercury |            
+ neptune |            
+ pluto   |            
+ saturn  |            
+ uranus  |            
+ venus   |            
+(9 rows)
+
+SELECT name, first_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |        4332
+ jupiter |        4332
+ mars    |        4332
+ mercury |        4332
+ neptune |        4332
+ pluto   |        4332
+ saturn  |        4332
+ uranus  |        4332
+ venus   |        4332
+(9 rows)
+
+SELECT name, last_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, last_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, last_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |        88
+ jupiter |        88
+ mars    |        88
+ mercury |        88
+ neptune |        88
+ pluto   |        88
+ saturn  |        88
+ uranus  |        88
+ venus   |        88
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM FIRST OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM FIRST IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |        88
+ jupiter |        88
+ mars    |        88
+ mercury |        88
+ neptune |        88
+ pluto   |        88
+ saturn  |        88
+ uranus  |        88
+ venus   |        88
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM FIRST RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM LAST OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |          
+ jupiter |          
+ mars    |          
+ mercury |          
+ neptune |          
+ pluto   |          
+ saturn  |          
+ uranus  |          
+ venus   |          
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM LAST IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |     24491
+ jupiter |     24491
+ mars    |     24491
+ mercury |     24491
+ neptune |     24491
+ pluto   |     24491
+ saturn  |     24491
+ uranus  |     24491
+ venus   |     24491
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) FROM LAST RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |          
+ jupiter |          
+ mars    |          
+ mercury |          
+ neptune |          
+ pluto   |          
+ saturn  |          
+ uranus  |          
+ venus   |          
+(9 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view v_planets
diff --git a/src/test/regress/sql/oidjoins.sql b/src/test/regress/sql/oidjoins.sql
index c8291d3973..cd05b0b632 100644
--- a/src/test/regress/sql/oidjoins.sql
+++ b/src/test/regress/sql/oidjoins.sql
@@ -449,10 +449,26 @@ SELECT	ctid, seqtypid
 FROM	pg_catalog.pg_sequence fk
 WHERE	seqtypid != 0 AND
 	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_type pk WHERE pk.oid = fk.seqtypid);
+SELECT	ctid, classid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	classid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_class pk WHERE pk.oid = fk.classid);
+SELECT	ctid, objid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	objid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_database pk WHERE pk.oid = fk.objid);
 SELECT	ctid, refclassid
 FROM	pg_catalog.pg_shdepend fk
 WHERE	refclassid != 0 AND
 	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_class pk WHERE pk.oid = fk.refclassid);
+SELECT	ctid, refobjid
+FROM	pg_catalog.pg_shdepend fk
+WHERE	refobjid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_authid pk WHERE pk.oid = fk.refobjid);
+SELECT	ctid, objoid
+FROM	pg_catalog.pg_shdescription fk
+WHERE	objoid != 0 AND
+	NOT EXISTS(SELECT 1 FROM pg_catalog.pg_database pk WHERE pk.oid = fk.objoid);
 SELECT	ctid, classoid
 FROM	pg_catalog.pg_shdescription fk
 WHERE	classoid != 0 AND
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index e2943a38f1..95d5125533 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1241,3 +1241,66 @@ SELECT to_char(SUM(n::float8) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FO
 SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
   FROM (VALUES (1,true), (2,true), (3,false), (4,false), (5,true)) v(i,b)
   WINDOW w AS (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FOLLOWING);
+
+-- FROM LAST and IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit int
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560);
+
+  -- test view definitions are preserved
+CREATE TEMP VIEW v_planets AS
+    SELECT
+      name,
+      sum(orbit) OVER (order by orbit) as sum_rows,
+      lag(orbit, 1) RESPECT NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+      lag(orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,
+      first_value(orbit) IGNORE NULLS OVER w AS first_value_ignore,
+      nth_value(orbit,2) FROM FIRST IGNORE NULLS OVER w AS nth_first_ignore,
+      nth_value(orbit,2) FROM LAST IGNORE NULLS OVER w AS nth_last_ignore
+    FROM planets
+    WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_planets');
+
+SELECT name, lag(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lag(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lag(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, lead(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, lag(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, first_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, first_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, first_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, last_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, last_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, last_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM FIRST OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM FIRST IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM FIRST RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM LAST OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM LAST IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) FROM LAST RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.17.1

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 28035f1635..3d73c96891 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -15702,7 +15702,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <function>
          lag(<replaceable class="parameter">value</replaceable> <type>anyelement</type>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</type>
-             [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]])
+             [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]]) [null_treatment]
        </function>
       </entry>
       <entry>
@@ -15731,7 +15731,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <function>
          lead(<replaceable class="parameter">value</replaceable> <type>anyelement</type>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</type>
-              [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]])
+              [, <replaceable class="parameter">default</replaceable> <type>anyelement</type> ]]) [null_treatment]
        </function>
       </entry>
       <entry>
@@ -15757,7 +15757,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <indexterm>
         <primary>first_value</primary>
        </indexterm>
-       <function>first_value(<replaceable class="parameter">value</replaceable> <type>any</type>)</function>
+       <function>first_value(<replaceable class="parameter">value</replaceable> <type>any</type>) [null_treatment]</function>
       </entry>
       <entry>
        <type>same type as <replaceable class="parameter">value</replaceable></type>
@@ -15773,7 +15773,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <indexterm>
         <primary>last_value</primary>
        </indexterm>
-       <function>last_value(<replaceable class="parameter">value</replaceable> <type>any</type>)</function>
+       <function>last_value(<replaceable class="parameter">value</replaceable> <type>any</type>) [null_treatment]</function>
       </entry>
       <entry>
        <type>same type as <replaceable class="parameter">value</replaceable></type>
@@ -15790,7 +15790,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <primary>nth_value</primary>
        </indexterm>
        <function>
-         nth_value(<replaceable class="parameter">value</replaceable> <type>any</type>, <replaceable class="parameter">nth</replaceable> <type>integer</type>)
+         nth_value(<replaceable class="parameter">value</replaceable> <type>any</type>, <replaceable class="parameter">nth</replaceable> <type>integer</type>) [null_treatment]
        </function>
       </entry>
       <entry>
@@ -15806,6 +15806,16 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
    </tgroup>
   </table>
 
+  <para>
+   In <xref linkend="functions-window-table"/>, <replaceable>null_treatment</replaceable> is one of:
+   <synopsis>
+     RESPECT NULLS
+     IGNORE NULLS
+   </synopsis>
+   <literal>RESPECT NULLS</literal> specifies the default behavior to include nulls in the result.
+   <literal>IGNORE NULLS</literal> ignores any null values when determining a result.
+  </para>
+
   <para>
    All of the functions listed in
    <xref linkend="functions-window-table"/> depend on the sort ordering
@@ -15843,17 +15853,11 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
 
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
-    ordering.)
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in <productname>PostgreSQL</productname>:
+    only the default <literal>FROM FIRST</literal> behavior is supported.
+    (You can achieve the result of <literal>FROM LAST</literal> by using negative number for the position argument,
+    as is done in many languages to indicate a <literal>FROM END</literal> index.)
    </para>
   </note>
 
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 9f840ddfd2..a355e379e7 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -508,9 +508,9 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE function			YES	
-T618	NTH_VALUE function			NO	function exists, but some options missing
+T618	NTH_VALUE function			YES	FROM LAST is supported by using negative number for the position argument
 T619	Nested window functions			NO	
 T620	WINDOW clause: GROUPS option			YES	
 T621	Enhanced numeric functions			YES	
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 96e7fdbcfe..db369b1f9a 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -154,6 +154,7 @@ static Node *makeBitStringConst(char *str, int location);
 static Node *makeNullAConst(int location);
 static Node *makeAConst(Value *v, int location);
 static Node *makeBoolAConst(bool state, int location);
+static Node *makeTypedBoolAConst(bool state, char *type, int location);
 static RoleSpec *makeRoleSpec(RoleSpecType type, int location);
 static void check_qualified_name(List *names, core_yyscan_t yyscanner);
 static List *check_func_name(List *names, core_yyscan_t yyscanner);
@@ -569,7 +570,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	xml_namespace_list
 %type <target>	xml_namespace_el
 
-%type <node>	func_application func_expr_common_subexpr
+%type <node>	func_application func_expr_common_subexpr func_expr_respect_ignore
 %type <node>	func_expr func_expr_windowless
 %type <node>	common_table_expr
 %type <with>	with_clause opt_with_clause
@@ -577,6 +578,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 %type <list>	within_group_clause
 %type <node>	filter_clause
+%type <ival>	null_treatment_clause
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
@@ -642,14 +644,14 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	EXCLUDE EXCLUDING EXCLUSIVE EXECUTE EXISTS EXPLAIN EXPRESSION
 	EXTENSION EXTERNAL EXTRACT
 
-	FALSE_P FAMILY FETCH FILTER FIRST_P FLOAT_P FOLLOWING FOR
+	FALSE_P FAMILY FETCH FILTER FIRST_P FIRST_VALUE FLOAT_P FOLLOWING FOR
 	FORCE FOREIGN FORWARD FREEZE FROM FULL FUNCTION FUNCTIONS
 
 	GENERATED GLOBAL GRANT GRANTED GREATEST GROUP_P GROUPING GROUPS
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -658,14 +660,14 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	KEY
 
-	LABEL LANGUAGE LARGE_P LAST_P LATERAL_P
-	LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
+	LABEL LAG LANGUAGE LARGE_P LAST_P LAST_VALUE LATERAL_P
+	LEAD LEADING LEAKPROOF LEAST LEFT LEVEL LIKE LIMIT LISTEN LOAD LOCAL
 	LOCALTIME LOCALTIMESTAMP LOCATION LOCK_P LOCKED LOGGED
 
 	MAPPING MATCH MATERIALIZED MAXVALUE METHOD MINUTE_P MINVALUE MODE MONTH_P MOVE
 
 	NAME_P NAMES NATIONAL NATURAL NCHAR NEW NEXT NO NONE
-	NOT NOTHING NOTIFY NOTNULL NOWAIT NULL_P NULLIF
+	NOT NOTHING NOTIFY NOTNULL NOWAIT NTH_VALUE NULL_P NULLIF
 	NULLS_P NUMERIC
 
 	OBJECT_P OF OFF OFFSET OIDS OLD ON ONLY OPERATOR OPTION OPTIONS OR
@@ -680,7 +682,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -724,6 +726,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 /* Precedence: lowest to highest */
 %nonassoc	SET				/* see relation_expr_opt_alias */
+%nonassoc	FIRST_VALUE LAG LAST_VALUE LEAD NTH_VALUE
 %left		UNION EXCEPT
 %left		INTERSECT
 %left		OR
@@ -13769,6 +13772,10 @@ func_application: func_name '(' ')'
 				}
 		;
 
+null_treatment_clause:
+			RESPECT NULLS_P			{ $$ = 0; }
+			| IGNORE_P NULLS_P		{ $$ = WINFUNC_OPT_IGNORE_NULLS; }
+		;
 
 /*
  * func_expr and its cousin func_expr_windowless are split out from c_expr just
@@ -13816,8 +13823,133 @@ func_expr: func_application within_group_clause filter_clause over_clause
 				}
 			| func_expr_common_subexpr
 				{ $$ = $1; }
+			| func_expr_respect_ignore over_clause
+				{
+					FuncCall *n = (FuncCall *) $1;
+					n->over = $2;
+					$$ = (Node *) n;
+				}
+		;
+
+func_expr_respect_ignore:
+			FIRST_VALUE '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("first_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| FIRST_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("first_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAG '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("lag")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAG '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("lag")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAST_VALUE '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("last_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LAST_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("last_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LEAD '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Ignore Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("lead")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| LEAD '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("lead")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| NTH_VALUE '(' func_arg_list opt_sort_clause ')' null_treatment_clause
+				{
+					FuncCall *n;
+					List *l = $3;
+					int winFuncArgs = $6;
+
+					/* Convert Nulls option to bool */
+					if (winFuncArgs & WINFUNC_OPT_IGNORE_NULLS)
+						l = lappend(l, makeTypedBoolAConst(true, "ignorenulls", @2));
+
+					n = makeFuncCall(list_make1(makeString("nth_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
+			| NTH_VALUE '(' func_arg_list opt_sort_clause ')'
+				{
+					FuncCall *n;
+					List *l = $3;
+
+					n = makeFuncCall(list_make1(makeString("nth_value")), l, @1);
+					n->agg_order = $4;
+					$$ = (Node *) n;
+				}
 		;
 
+
 /*
  * As func_expr but does not accept WINDOW functions directly
  * (but they can still be contained in arguments for functions etc).
@@ -15225,6 +15357,7 @@ unreserved_keyword:
 			| FAMILY
 			| FILTER
 			| FIRST_P
+			| FIRST_VALUE
 			| FOLLOWING
 			| FORCE
 			| FORWARD
@@ -15240,6 +15373,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -15260,9 +15394,12 @@ unreserved_keyword:
 			| ISOLATION
 			| KEY
 			| LABEL
+			| LAG
 			| LANGUAGE
 			| LARGE_P
 			| LAST_P
+			| LAST_VALUE
+			| LEAD
 			| LEAKPROOF
 			| LEVEL
 			| LISTEN
@@ -15290,6 +15427,7 @@ unreserved_keyword:
 			| NOTHING
 			| NOTIFY
 			| NOWAIT
+			| NTH_VALUE
 			| NULLS_P
 			| OBJECT_P
 			| OF
@@ -15341,6 +15479,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
@@ -15815,6 +15954,15 @@ makeAConst(Value *v, int location)
  */
 static Node *
 makeBoolAConst(bool state, int location)
+{
+	return makeTypedBoolAConst(state, "bool", location);
+}
+
+/* makeTypedBoolAConst()
+ * Create an A_Const string node from a boolean and store inside the specified type.
+ */
+static Node *
+makeTypedBoolAConst(bool state, char *type, int location)
 {
 	A_Const *n = makeNode(A_Const);
 
@@ -15822,7 +15970,7 @@ makeBoolAConst(bool state, int location)
 	n->val.val.str = (state ? "t" : "f");
 	n->location = location;
 
-	return makeTypeCast((Node *)n, SystemTypeName("bool"), -1);
+	return makeTypeCast((Node *)n, SystemTypeName(type), -1);
 }
 
 /* makeRoleSpec
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 158784474d..ae7e821ab2 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -9437,6 +9437,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 	int			nargs;
 	List	   *argnames;
 	ListCell   *l;
+	bool		ignorenulls = false;
 
 	if (list_length(wfunc->args) > FUNC_MAX_ARGS)
 		ereport(ERROR,
@@ -9463,7 +9464,32 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 	if (wfunc->winstar)
 		appendStringInfoChar(buf, '*');
 	else
-		get_rule_expr((Node *) wfunc->args, context, true);
+	{
+		ListCell	*arglist;
+		Node *argnode = (Node *) wfunc->args;
+
+		get_rule_expr(argnode, context, true);
+
+		/* Determine if IGNORE NULLS should be appended */
+		foreach(arglist, (List *) argnode)
+		{
+			Node *arg = (Node *) lfirst(arglist);
+			if (nodeTag(arg) == T_Const)
+			{
+				Const *constnode = (Const *) arg;
+				if (constnode->consttype == IGNORENULLSOID)
+				{
+					/* parser does not save RESPECT NULLS arguments */
+					ignorenulls = true;
+					buf->len -= 2;
+				}
+			}
+		}
+        }
+
+	appendStringInfoChar(buf, ')');
+	if (ignorenulls)
+		appendStringInfoString(buf, " IGNORE NULLS");
 
 	if (wfunc->aggfilter != NULL)
 	{
@@ -9471,7 +9497,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, " OVER ");
 
 	foreach(l, context->windowClause)
 	{
@@ -9649,6 +9675,10 @@ get_const_expr(Const *constval, deparse_context *context, int showtype)
 				appendStringInfoString(buf, "false");
 			break;
 
+		case IGNORENULLSOID:
+			showtype = -1;
+			break;
+
 		default:
 			simple_quote_literal(buf, extval);
 			break;
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index f0c8ae686d..bc639b1883 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -38,7 +38,12 @@ typedef struct
 static bool rank_up(WindowObject winobj);
 static Datum leadlag_common(FunctionCallInfo fcinfo,
 							bool forward, bool withoffset, bool withdefault);
-
+static Datum leadlag_common_ignore_nulls(FunctionCallInfo fcinfo,
+							bool forward, bool withoffset, bool withdefault);
+static Datum
+window_nth_value_ignorenulls_common(FunctionCallInfo fcinfo, int32 nth);
+static Datum
+window_nth_value_respectnulls_common(FunctionCallInfo fcinfo, int32 nth);
 
 /*
  * utility routine for *_rank functions.
@@ -328,6 +333,79 @@ leadlag_common(FunctionCallInfo fcinfo,
 	PG_RETURN_DATUM(result);
 }
 
+static Datum
+leadlag_common_ignore_nulls(FunctionCallInfo fcinfo,
+			    bool forward, bool withoffset, bool withdefault)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	int32           offset;
+	Datum           result;
+	bool            isnull;
+	bool            isout = false;
+	int32           notnull_offset = 0, tmp_offset = 0;
+
+	if (withoffset)
+	{
+		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+		if (isnull)
+			PG_RETURN_NULL();
+		if (offset < 0)
+		{
+			offset = abs(offset);
+			forward = !forward;
+		} else if (offset == 0)
+		{
+			result = WinGetFuncArgInPartition(winobj, 0, 0,
+									    WINDOW_SEEK_CURRENT,
+									    false,
+									    &isnull, &isout);
+			if (isnull || isout)
+				PG_RETURN_NULL();
+			else
+				PG_RETURN_DATUM(result);
+		}
+	}
+	else
+		offset = 1;
+
+	while (notnull_offset < offset)
+	{
+		tmp_offset++;
+		result = WinGetFuncArgInPartition(winobj, 0,
+									    (forward ? tmp_offset : -tmp_offset),
+									    WINDOW_SEEK_CURRENT,
+									    false,
+									    &isnull, &isout);
+		if (isout)
+			goto out_of_frame;
+		else if (!isnull)
+			notnull_offset++;
+	}
+
+	result = WinGetFuncArgInPartition(winobj, 0,
+									    (forward ? tmp_offset : -tmp_offset),
+									    WINDOW_SEEK_CURRENT,
+									    false,
+									    &isnull, &isout);
+	if (isout)
+		goto out_of_frame;
+	else
+		PG_RETURN_DATUM(result);
+
+	out_of_frame:
+	/*
+	* target row is out of the partition; supply default value if
+	* provided. Otherwise return NULL.
+	*/
+	if (withdefault)
+	{
+		result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		PG_RETURN_DATUM(result);
+	}
+	else
+		PG_RETURN_NULL();
+}
+
 /*
  * lag
  * returns the value of VE evaluated on a row that is 1
@@ -363,6 +441,24 @@ window_lag_with_offset_and_default(PG_FUNCTION_ARGS)
 	return leadlag_common(fcinfo, false, true, true);
 }
 
+Datum
+window_lag_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, false, false);
+}
+
+Datum
+window_lag_with_offset_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, true, false);
+}
+
+Datum
+window_lag_with_offset_and_default_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, false, true, true);
+}
+
 /*
  * lead
  * returns the value of VE evaluated on a row that is 1
@@ -398,6 +494,24 @@ window_lead_with_offset_and_default(PG_FUNCTION_ARGS)
 	return leadlag_common(fcinfo, true, true, true);
 }
 
+Datum
+window_lead_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, false, false);
+}
+
+Datum
+window_lead_with_offset_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, true, false);
+}
+
+Datum
+window_lead_with_offset_and_default_nulls_opt(PG_FUNCTION_ARGS)
+{
+	return leadlag_common_ignore_nulls(fcinfo, true, true, true);
+}
+
 /*
  * first_value
  * return the value of VE evaluated on the first row of the
@@ -419,6 +533,31 @@ window_first_value(PG_FUNCTION_ARGS)
 	PG_RETURN_DATUM(result);
 }
 
+Datum
+window_first_value_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	int64		pos;
+
+	isout = false;
+	pos = 0;
+
+	while (!isout)
+	{
+		result = WinGetFuncArgInFrame(winobj, 0,
+							    pos, WINDOW_SEEK_HEAD, false,
+							    &isnull, &isout);
+	if (!isnull)
+		PG_RETURN_DATUM(result);
+	pos++;
+	}
+
+	PG_RETURN_NULL();
+}
+
 /*
  * last_value
  * return the value of VE evaluated on the last row of the
@@ -440,35 +579,149 @@ window_last_value(PG_FUNCTION_ARGS)
 	PG_RETURN_DATUM(result);
 }
 
+Datum
+window_last_value_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	int64		pos;
+
+	isout = false;
+	pos = 0;
+
+	while (!isout)
+	{
+		result = WinGetFuncArgInFrame(winobj, 0,
+								    pos, WINDOW_SEEK_TAIL, false,
+								    &isnull, &isout);
+		if (!isnull)
+			PG_RETURN_DATUM(result);
+		pos--;
+	}
+
+	PG_RETURN_NULL();
+}
+
 /*
  * nth_value
  * return the value of VE evaluated on the n-th row from the first
  * row of the window frame, per spec.
  */
-Datum
-window_nth_value(PG_FUNCTION_ARGS)
+static Datum
+window_nth_value_respectnulls_common(FunctionCallInfo fcinfo, int32 nth)
 {
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	bool		const_offset;
 	Datum		result;
 	bool		isnull;
-	int32		nth;
+	bool		fromlast;
 
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
 	const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
 
-	if (nth <= 0)
+	if (nth == 0)
 		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
-				 errmsg("argument of nth_value must be greater than zero")));
+		(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
+		errmsg("argument of nth_value must be greater or less than zero")));
+	else if (nth < 0)
+	{
+		nth = abs(nth);
+		fromlast = true;
+	}
+	else
+		fromlast = false;
+
+	result = WinGetFuncArgInFrame(winobj,
+								0,
+								nth - 1,
+								fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD, const_offset,
+								&isnull,
+								NULL);
 
-	result = WinGetFuncArgInFrame(winobj, 0,
-								  nth - 1, WINDOW_SEEK_HEAD, const_offset,
-								  &isnull, NULL);
 	if (isnull)
 		PG_RETURN_NULL();
 
 	PG_RETURN_DATUM(result);
 }
+
+static Datum
+window_nth_value_ignorenulls_common(FunctionCallInfo fcinfo, int32 nth)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	Datum		result;
+	bool		isnull,
+				isout;
+	bool		fromlast;
+	int32		tmp_offset, notnull_offset = 0;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+
+	if (nth == 0)
+		ereport(ERROR,
+		(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
+		errmsg("argument of nth_value must be greater or less than zero")));
+	else if (nth < 0)
+	{
+		nth = abs(nth);
+		fromlast = true;
+		tmp_offset = 1;
+	}
+	else
+	{
+		fromlast = false;
+		tmp_offset = -1;
+	}
+
+	while (notnull_offset < nth)
+	{
+		fromlast ? tmp_offset-- : tmp_offset++;
+		result = WinGetFuncArgInFrame(winobj, 0,
+									tmp_offset, fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD,
+									false, &isnull, &isout);
+		if (isout)
+			PG_RETURN_NULL();
+		if (!isnull)
+			notnull_offset++;
+	}
+
+	result = WinGetFuncArgInFrame(winobj, 0,
+								tmp_offset, fromlast ? WINDOW_SEEK_TAIL : WINDOW_SEEK_HEAD,
+								false, &isnull, &isout);
+
+	if (isout || isnull)
+		PG_RETURN_NULL();
+
+	PG_RETURN_DATUM(result);
+}
+
+Datum
+window_nth_value(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_respectnulls_common(fcinfo, nth));
+}
+
+Datum
+window_nth_value_with_nulls_opt(PG_FUNCTION_ARGS)
+{
+	WindowObject winobj = PG_WINDOW_OBJECT();
+	bool		isnull;
+	int32		nth;
+
+	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
+	if (isnull)
+		PG_RETURN_NULL();
+	PG_RETURN_DATUM(window_nth_value_ignorenulls_common(fcinfo, nth));
+}
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
index 07a86c7b7b..f07a9e442d 100644
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -9539,32 +9539,64 @@
 { oid => '3106', descr => 'fetch the preceding row value',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_lag' },
+{ oid => '4191', descr => 'fetch the preceding row value with nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_lag_nulls_opt' },
 { oid => '3107', descr => 'fetch the Nth preceding row value',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_lag_with_offset' },
+{ oid => '4192', descr => 'fetch the Nth preceding row value with nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_lag_with_offset_nulls_opt' },
 { oid => '3108', descr => 'fetch the Nth preceding row value with default',
   proname => 'lag', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4 anyelement',
   prosrc => 'window_lag_with_offset_and_default' },
+{ oid => '4193', descr => 'fetch the Nth preceding row value with default and nulls option',
+  proname => 'lag', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 anyelement ignorenulls',
+  prosrc => 'window_lag_with_offset_and_default_nulls_opt' },
 { oid => '3109', descr => 'fetch the following row value',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_lead' },
+{ oid => '4194', descr => 'fetch the following row value with nulls option',
+ proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+ proargtypes => 'anyelement ignorenulls', prosrc => 'window_lead_nulls_opt' },
 { oid => '3110', descr => 'fetch the Nth following row value',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_lead_with_offset' },
+{ oid => '4195', descr => 'fetch the Nth following row value with nulls option',
+  proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_lead_with_offset_nulls_opt' },
 { oid => '3111', descr => 'fetch the Nth following row value with default',
   proname => 'lead', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4 anyelement',
   prosrc => 'window_lead_with_offset_and_default' },
+{ oid => '4196', descr => 'fetch the Nth following row value with default and nulls option',
+  proname => 'lead', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 anyelement ignorenulls',
+  prosrc => 'window_lead_with_offset_and_default_nulls_opt' },
 { oid => '3112', descr => 'fetch the first row value',
   proname => 'first_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_first_value' },
+{ oid => '4197', descr => 'fetch the first row value with nulls option',
+  proname => 'first_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_first_value_nulls_opt' },
 { oid => '3113', descr => 'fetch the last row value',
   proname => 'last_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement', prosrc => 'window_last_value' },
+{ oid => '4198', descr => 'fetch the last row value with nulls option',
+  proname => 'last_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement ignorenulls', prosrc => 'window_last_value_nulls_opt' },
 { oid => '3114', descr => 'fetch the Nth row value',
   proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
   proargtypes => 'anyelement int4', prosrc => 'window_nth_value' },
+{ oid => '4199', descr => 'fetch the Nth row value with nulls option',
+  proname => 'nth_value', prokind => 'w', prorettype => 'anyelement',
+  proargtypes => 'anyelement int4 ignorenulls',
+  prosrc => 'window_nth_value_with_nulls_opt' },
 
 # functions for range types
 { oid => '3832', descr => 'I/O',
diff --git a/src/include/catalog/pg_type.dat b/src/include/catalog/pg_type.dat
index 4cf2b9df7b..3c847e6db5 100644
--- a/src/include/catalog/pg_type.dat
+++ b/src/include/catalog/pg_type.dat
@@ -594,5 +594,10 @@
   typname => 'anyrange', typlen => '-1', typbyval => 'f', typtype => 'p',
   typcategory => 'P', typinput => 'anyrange_in', typoutput => 'anyrange_out',
   typreceive => '-', typsend => '-', typalign => 'd', typstorage => 'x' },
+{ oid => '4142',
+  descr => 'boolean wrapper, \'true\'/\'false\'',
+  typname => 'ignorenulls', typlen => '1', typbyval => 't', typtype => 'b',
+  typcategory => 'B', typinput => 'boolin', typoutput => 'boolout',
+  typreceive => 'boolrecv', typsend => 'boolsend', typalign => 'c' },
 
 ]
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index da0706add5..0899bddd6e 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -532,6 +532,11 @@ typedef struct WindowDef
 	(FRAMEOPTION_RANGE | FRAMEOPTION_START_UNBOUNDED_PRECEDING | \
 	 FRAMEOPTION_END_CURRENT_ROW)
 
+/*
+ * Null Treatment option
+ */
+#define WINFUNC_OPT_IGNORE_NULLS			0x00001 /* IGNORE NULLS */
+
 /*
  * RangeSubselect - subquery appearing in a FROM clause
  */
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b1184c2d15..a33ce1d0fd 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -164,6 +164,7 @@ PG_KEYWORD("family", FAMILY, UNRESERVED_KEYWORD)
 PG_KEYWORD("fetch", FETCH, RESERVED_KEYWORD)
 PG_KEYWORD("filter", FILTER, UNRESERVED_KEYWORD)
 PG_KEYWORD("first", FIRST_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("first_value", FIRST_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("float", FLOAT_P, COL_NAME_KEYWORD)
 PG_KEYWORD("following", FOLLOWING, UNRESERVED_KEYWORD)
 PG_KEYWORD("for", FOR, RESERVED_KEYWORD)
@@ -190,6 +191,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -223,10 +225,13 @@ PG_KEYWORD("isolation", ISOLATION, UNRESERVED_KEYWORD)
 PG_KEYWORD("join", JOIN, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("key", KEY, UNRESERVED_KEYWORD)
 PG_KEYWORD("label", LABEL, UNRESERVED_KEYWORD)
+PG_KEYWORD("lag", LAG, UNRESERVED_KEYWORD)
 PG_KEYWORD("language", LANGUAGE, UNRESERVED_KEYWORD)
 PG_KEYWORD("large", LARGE_P, UNRESERVED_KEYWORD)
 PG_KEYWORD("last", LAST_P, UNRESERVED_KEYWORD)
+PG_KEYWORD("last_value", LAST_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("lateral", LATERAL_P, RESERVED_KEYWORD)
+PG_KEYWORD("lead", LEAD, UNRESERVED_KEYWORD)
 PG_KEYWORD("leading", LEADING, RESERVED_KEYWORD)
 PG_KEYWORD("leakproof", LEAKPROOF, UNRESERVED_KEYWORD)
 PG_KEYWORD("least", LEAST, COL_NAME_KEYWORD)
@@ -267,6 +272,7 @@ PG_KEYWORD("nothing", NOTHING, UNRESERVED_KEYWORD)
 PG_KEYWORD("notify", NOTIFY, UNRESERVED_KEYWORD)
 PG_KEYWORD("notnull", NOTNULL, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("nowait", NOWAIT, UNRESERVED_KEYWORD)
+PG_KEYWORD("nth_value", NTH_VALUE, UNRESERVED_KEYWORD)
 PG_KEYWORD("null", NULL_P, RESERVED_KEYWORD)
 PG_KEYWORD("nullif", NULLIF, COL_NAME_KEYWORD)
 PG_KEYWORD("nulls", NULLS_P, UNRESERVED_KEYWORD)
@@ -336,6 +342,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD)
+PG_KEYWORD("respect", RESPECT, UNRESERVED_KEYWORD)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD)
 PG_KEYWORD("returning", RETURNING, RESERVED_KEYWORD)
diff --git a/src/test/regress/expected/type_sanity.out b/src/test/regress/expected/type_sanity.out
index cd7fc03b04..0ac49263ec 100644
--- a/src/test/regress/expected/type_sanity.out
+++ b/src/test/regress/expected/type_sanity.out
@@ -73,7 +73,8 @@ WHERE p1.typtype not in ('c','d','p') AND p1.typname NOT LIKE E'\\_%'
  3361 | pg_ndistinct
  3402 | pg_dependencies
  5017 | pg_mcv_list
-(4 rows)
+ 4142 | ignorenulls
+(5 rows)
 
 -- Make sure typarray points to a varlena array type of our own base
 SELECT p1.oid, p1.typname as basetype, p2.typname as arraytype,
@@ -166,10 +167,11 @@ WHERE p1.typinput = p2.oid AND p1.typtype in ('b', 'p') AND NOT
     (p1.typelem != 0 AND p1.typlen < 0) AND NOT
     (p2.prorettype = p1.oid AND NOT p2.proretset)
 ORDER BY 1;
- oid  |  typname  | oid | proname 
-------+-----------+-----+---------
- 1790 | refcursor |  46 | textin
-(1 row)
+ oid  |   typname   | oid  | proname 
+------+-------------+------+---------
+ 1790 | refcursor   |   46 | textin
+ 4142 | ignorenulls | 1242 | boolin
+(2 rows)
 
 -- Varlena array types will point to array_in
 -- Exception as of 8.1: int2vector and oidvector have their own I/O routines
@@ -217,10 +219,11 @@ WHERE p1.typoutput = p2.oid AND p1.typtype in ('b', 'p') AND NOT
       (p2.oid = 'array_out'::regproc AND
        p1.typelem != 0 AND p1.typlen = -1)))
 ORDER BY 1;
- oid  |  typname  | oid | proname 
-------+-----------+-----+---------
- 1790 | refcursor |  47 | textout
-(1 row)
+ oid  |   typname   | oid  | proname 
+------+-------------+------+---------
+ 1790 | refcursor   |   47 | textout
+ 4142 | ignorenulls | 1243 | boolout
+(2 rows)
 
 SELECT p1.oid, p1.typname, p2.oid, p2.proname
 FROM pg_type AS p1, pg_proc AS p2
@@ -280,10 +283,11 @@ WHERE p1.typreceive = p2.oid AND p1.typtype in ('b', 'p') AND NOT
     (p1.typelem != 0 AND p1.typlen < 0) AND NOT
     (p2.prorettype = p1.oid AND NOT p2.proretset)
 ORDER BY 1;
- oid  |  typname  | oid  | proname  
-------+-----------+------+----------
- 1790 | refcursor | 2414 | textrecv
-(1 row)
+ oid  |   typname   | oid  | proname  
+------+-------------+------+----------
+ 1790 | refcursor   | 2414 | textrecv
+ 4142 | ignorenulls | 2436 | boolrecv
+(2 rows)
 
 -- Varlena array types will point to array_recv
 -- Exception as of 8.1: int2vector and oidvector have their own I/O routines
@@ -340,10 +344,11 @@ WHERE p1.typsend = p2.oid AND p1.typtype in ('b', 'p') AND NOT
       (p2.oid = 'array_send'::regproc AND
        p1.typelem != 0 AND p1.typlen = -1)))
 ORDER BY 1;
- oid  |  typname  | oid  | proname  
-------+-----------+------+----------
- 1790 | refcursor | 2415 | textsend
-(1 row)
+ oid  |   typname   | oid  | proname  
+------+-------------+------+----------
+ 1790 | refcursor   | 2415 | textsend
+ 4142 | ignorenulls | 2437 | boolsend
+(2 rows)
 
 SELECT p1.oid, p1.typname, p2.oid, p2.proname
 FROM pg_type AS p1, pg_proc AS p2
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index d5fd4045f9..54ded65906 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -2985,7 +2985,7 @@ LINE 1: SELECT generate_series(1, 100) OVER () FROM empsalary;
 SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 ERROR:  argument of ntile must be greater than zero
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
-ERROR:  argument of nth_value must be greater than zero
+ERROR:  argument of nth_value must be greater or less than zero
 -- filter
 SELECT sum(salary), row_number() OVER (ORDER BY depname), sum(
     sum(salary) FILTER (WHERE enroll_date > '2007-01-01')
@@ -3863,3 +3863,369 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- RESPECT NULLS and IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit int
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560);
+  -- test view definitions are preserved
+CREATE TEMP VIEW v_planets AS
+    SELECT
+      name,
+      sum(orbit) OVER (order by orbit) as sum_rows,
+      lag(orbit, 1) RESPECT NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+      lag(orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,
+      first_value(orbit) IGNORE NULLS OVER w AS first_value_ignore,
+      nth_value(orbit,2) IGNORE NULLS OVER w AS nth_first_ignore,
+      nth_value(orbit,-2) IGNORE NULLS OVER w AS nth_last_ignore
+    FROM planets
+    WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_planets');
+                                   pg_get_viewdef                                   
+------------------------------------------------------------------------------------
+  SELECT planets.name,                                                             +
+     sum(planets.orbit) OVER (ORDER BY planets.orbit) AS sum_rows,                 +
+     lag(planets.orbit, 1) OVER (ORDER BY planets.name DESC) AS lagged_by_1,       +
+     lag(planets.orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,                     +
+     first_value(planets.orbit) IGNORE NULLS OVER w AS first_value_ignore,         +
+     nth_value(planets.orbit, 2) IGNORE NULLS OVER w AS nth_first_ignore,          +
+     nth_value(planets.orbit, '-2'::integer) IGNORE NULLS OVER w AS nth_last_ignore+
+    FROM planets                                                                   +
+   WINDOW w AS (ORDER BY planets.name);
+(1 row)
+
+SELECT name, lag(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |      
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |      
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |  4332
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   | 24491
+(9 rows)
+
+SELECT name, lead(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |      
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |      
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |      
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |      
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |  4332
+ jupiter |    88
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |   224
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lag(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   |  lag  
+---------+-------
+ earth   |  4332
+ jupiter |    88
+ mars    |    88
+ mercury | 60182
+ neptune | 90560
+ pluto   | 24491
+ saturn  |   224
+ uranus  |   224
+ venus   |      
+(9 rows)
+
+SELECT name, lead(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | lead  
+---------+-------
+ earth   |      
+ jupiter |      
+ mars    |  4332
+ mercury |  4332
+ neptune |    88
+ pluto   | 60182
+ saturn  | 90560
+ uranus  | 24491
+ venus   | 24491
+(9 rows)
+
+SELECT name, first_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |            
+ jupiter |            
+ mars    |            
+ mercury |            
+ neptune |            
+ pluto   |            
+ saturn  |            
+ uranus  |            
+ venus   |            
+(9 rows)
+
+SELECT name, first_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |            
+ jupiter |            
+ mars    |            
+ mercury |            
+ neptune |            
+ pluto   |            
+ saturn  |            
+ uranus  |            
+ venus   |            
+(9 rows)
+
+SELECT name, first_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | first_value 
+---------+-------------
+ earth   |        4332
+ jupiter |        4332
+ mars    |        4332
+ mercury |        4332
+ neptune |        4332
+ pluto   |        4332
+ saturn  |        4332
+ uranus  |        4332
+ venus   |        4332
+(9 rows)
+
+SELECT name, last_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, last_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, last_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | last_value 
+---------+------------
+ earth   |        224
+ jupiter |        224
+ mars    |        224
+ mercury |        224
+ neptune |        224
+ pluto   |        224
+ saturn  |        224
+ uranus  |        224
+ venus   |        224
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |        88
+ jupiter |        88
+ mars    |        88
+ mercury |        88
+ neptune |        88
+ pluto   |        88
+ saturn  |        88
+ uranus  |        88
+ venus   |        88
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |        88
+ jupiter |        88
+ mars    |        88
+ mercury |        88
+ neptune |        88
+ pluto   |        88
+ saturn  |        88
+ uranus  |        88
+ venus   |        88
+(9 rows)
+
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |      4332
+ jupiter |      4332
+ mars    |      4332
+ mercury |      4332
+ neptune |      4332
+ pluto   |      4332
+ saturn  |      4332
+ uranus  |      4332
+ venus   |      4332
+(9 rows)
+
+SELECT name, nth_value(orbit, -2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |          
+ jupiter |          
+ mars    |          
+ mercury |          
+ neptune |          
+ pluto   |          
+ saturn  |          
+ uranus  |          
+ venus   |          
+(9 rows)
+
+SELECT name, nth_value(orbit, -2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |     24491
+ jupiter |     24491
+ mars    |     24491
+ mercury |     24491
+ neptune |     24491
+ pluto   |     24491
+ saturn  |     24491
+ uranus  |     24491
+ venus   |     24491
+(9 rows)
+
+SELECT name, nth_value(orbit, -2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+  name   | nth_value 
+---------+-----------
+ earth   |          
+ jupiter |          
+ mars    |          
+ mercury |          
+ neptune |          
+ pluto   |          
+ saturn  |          
+ uranus  |          
+ venus   |          
+(9 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view v_planets
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index fe273aa31e..548902d482 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1276,3 +1276,67 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- RESPECT NULLS and IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit int
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560);
+
+  -- test view definitions are preserved
+CREATE TEMP VIEW v_planets AS
+    SELECT
+      name,
+      sum(orbit) OVER (order by orbit) as sum_rows,
+      lag(orbit, 1) RESPECT NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+      lag(orbit, 2) IGNORE NULLS OVER w AS lagged_by_2,
+      first_value(orbit) IGNORE NULLS OVER w AS first_value_ignore,
+      nth_value(orbit,2) IGNORE NULLS OVER w AS nth_first_ignore,
+      nth_value(orbit,-2) IGNORE NULLS OVER w AS nth_last_ignore
+    FROM planets
+    WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_planets');
+
+SELECT name, lag(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lag(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lag(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, lead(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, lag(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, lead(orbit, -1) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, first_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, first_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, first_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, last_value(orbit) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, last_value(orbit) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, last_value(orbit) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+SELECT name, nth_value(orbit, 2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, 2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, -2) OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, -2) IGNORE NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+SELECT name, nth_value(orbit, -2) RESPECT NULLS OVER (ORDER BY name range between unbounded preceding and unbounded following) FROM planets ORDER BY name;
+
+--cleanup
+DROP TABLE planets CASCADE;

From 07f01f8859e159c908ada72e8f53daf51e0b8bdf Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 22 Apr 2023 16:52:50 +0900
Subject: [PATCH v1 1/3] Implement IGNORE or RESPECT NULLS parse/analysis part.

Implement SQL standard's IGNORE/RESPECT NULLS clause for window functions.
For now, only nth_value() can use this option.
---
 src/backend/parser/gram.y       | 22 ++++++++++++++++++----
 src/backend/parser/parse_func.c | 13 +++++++++++++
 src/include/nodes/parsenodes.h  |  8 ++++++++
 src/include/nodes/primnodes.h   |  2 ++
 src/include/parser/kwlist.h     |  2 ++
 5 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index acf6cf4866..2980ecd666 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -276,6 +276,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	MergeWhenClause *mergewhen;
 	struct KeyActions *keyactions;
 	struct KeyAction *keyaction;
+	NullTreatment	nulltreatment;
 }
 
 %type <node>	stmt toplevel_stmt schema_stmt routine_body_stmt
@@ -661,6 +662,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 					json_object_constructor_null_clause_opt
 					json_array_constructor_null_clause_opt
 
+%type <nulltreatment>		opt_null_treatment
+
 /*
  * Non-keyword token types.  These are hard-wired into the "flex" lexer.
  * They must be listed first so that their numeric codes do not depend on
@@ -718,7 +721,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -752,7 +755,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15213,7 +15216,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause opt_null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15246,7 +15249,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->null_treatment = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -15790,6 +15794,14 @@ filter_clause:
 			| /*EMPTY*/								{ $$ = NULL; }
 		;
 
+/*
+ * Window function option clauses
+ */
+opt_null_treatment:
+			RESPECT NULLS_P							{ $$ = RESPECT_NULLS; }
+			| IGNORE_P NULLS_P						{ $$ = IGNORE_NULLS; }
+			| /*EMPTY*/								{ $$ = NULL_TREATMENT_NOT_SET; }
+		;
 
 /*
  * Window Definitions
@@ -17111,6 +17123,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17223,6 +17236,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index b3f0b6a137..92af0d10f1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -31,6 +31,7 @@
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
 #include "utils/builtins.h"
+#include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
 
@@ -99,6 +100,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
+	NullTreatment null_treatment = (fn ? fn->null_treatment : NULL_TREATMENT_NOT_SET);
 	bool		could_be_projection;
 	Oid			rettype;
 	Oid			funcid;
@@ -534,6 +536,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("window function %s cannot have WITHIN GROUP",
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
+		/* Check RESPECT NULLS or IGNORE NULLS is specified. They are only allowed with nth_value */
+		if (null_treatment != NULL_TREATMENT_NOT_SET && funcid != F_NTH_VALUE)
+			ereport(ERROR,
+					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+					 errmsg("window function %s cannot have RESPECT NULLS or IGNORE NULLS",
+							NameListToString(funcname)),
+					 parser_errposition(pstate, location)));
 	}
 	else if (fdresult == FUNCDETAIL_COERCION)
 	{
@@ -835,6 +844,10 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
 		wfunc->location = location;
+		if (null_treatment == IGNORE_NULLS)
+			wfunc->ignorenulls = true;
+		else
+			wfunc->ignorenulls = false;
 
 		/*
 		 * agg_star is allowed for aggregate functions but distinct isn't
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index cc7b32b279..f13ae26a24 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -404,6 +404,13 @@ typedef struct RoleSpec
 	int			location;		/* token location, or -1 if unknown */
 } RoleSpec;
 
+typedef enum NullTreatment
+{
+	NULL_TREATMENT_NOT_SET = 0,
+	RESPECT_NULLS,
+	IGNORE_NULLS
+} NullTreatment;
+
 /*
  * FuncCall - a function or aggregate invocation
  *
@@ -431,6 +438,7 @@ typedef struct FuncCall
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
 	bool		func_variadic;	/* last argument was labeled VARIADIC */
 	CoercionForm funcformat;	/* how to display this node */
+	NullTreatment null_treatment;	/* RESPECT_NULLS or IGNORE NULLS */
 	int			location;		/* token location, or -1 if unknown */
 } FuncCall;
 
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index be9c29f0bf..213297dbd3 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -559,6 +559,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* true if IGNORE NULLS, false if RESPECT NULLS */
+	bool		ignorenulls pg_node_attr(query_jumble_ignore);
 	/* token location, or -1 if unknown */
 	int			location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f5b2e61ca5..c7e61a8f0e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -198,6 +198,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -360,6 +361,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.25.1

From 3dc6f4bb897f76247589db018716bf5680d5331c Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 22 Apr 2023 16:58:48 +0900
Subject: [PATCH v1 2/3] Implement IGNORE or RESPECT NULLS planner part.

---
 src/backend/optimizer/util/clauses.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index a9c7bc342e..40fc62c447 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2474,6 +2474,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignorenulls = expr->ignorenulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
-- 
2.25.1

From a78feec9bf7b08c644c2b3089b2de9237d4fcd9e Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 22 Apr 2023 17:00:06 +0900
Subject: [PATCH v1 3/3] Implement IGNORE or RESPECT NULLS executor and window
 functions part.

---
 src/backend/executor/nodeWindowAgg.c | 11 ++++++++++
 src/backend/utils/adt/windowfuncs.c  | 30 +++++++++++++++++++++++++---
 src/include/windowapi.h              |  2 ++
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 3ac581a711..7e2affb12c 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	WindowFunc	*wfunc;			/* WindowFunc of this function */
 } WindowObjectData;
 
 /*
@@ -2617,6 +2618,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->winstate = winstate;
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
+			winobj->wfunc = wfunc;
 			perfuncstate->winobj = winobj;
 
 			/* It's a real window function, so set up to call it. */
@@ -3620,3 +3622,12 @@ WinGetFuncArgCurrent(WindowObject winobj, int argno, bool *isnull)
 	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
 						econtext, isnull);
 }
+
+/*
+ * Return current WindowFunc
+ */
+WindowFunc	*
+WinGetWindowFunc(WindowObject winobj)
+{
+	return winobj->wfunc;
+}
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b87a624fb2..919295ba13 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -693,6 +693,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		const_offset;
 	Datum		result;
 	bool		isnull;
+	bool		isout;
 	int32		nth;
 
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -705,9 +706,32 @@ window_nth_value(PG_FUNCTION_ARGS)
 				(errcode(ERRCODE_INVALID_ARGUMENT_FOR_NTH_VALUE),
 				 errmsg("argument of nth_value must be greater than zero")));
 
-	result = WinGetFuncArgInFrame(winobj, 0,
-								  nth - 1, WINDOW_SEEK_HEAD, const_offset,
-								  &isnull, NULL);
+	if (WinGetWindowFunc(winobj)->ignorenulls)
+	{
+		int		i, n;
+
+		i = n = 0;
+
+		for (;;)
+		{
+			result = WinGetFuncArgInFrame(winobj, 0,
+										  i++, WINDOW_SEEK_HEAD, false,
+										  &isnull, &isout);
+			if (isout)
+				break;
+
+			if (!isnull)
+			{
+				if (n == nth - 1)
+					break;
+				n++;
+			}
+		}
+	}
+	else
+		result = WinGetFuncArgInFrame(winobj, 0,
+									  nth - 1, WINDOW_SEEK_HEAD, const_offset,
+									  &isnull, NULL);
 	if (isnull)
 		PG_RETURN_NULL();
 
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index b8c2c565d1..64f7d4c84d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -61,4 +61,6 @@ extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
 extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
 								  bool *isnull);
 
+extern WindowFunc	*WinGetWindowFunc(WindowObject winobj);
+
 #endif							/* WINDOWAPI_H */
-- 
2.25.1

From 81c48df9a08deb065379e8bccffb2f5592faa4d0 Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Wed, 19 Apr 2023 01:07:14 +0100
Subject: [PATCH] initial window ignore

---
 src/backend/executor/nodeWindowAgg.c | 263 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  20 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |   2 +
 src/include/parser/kwlist.h          |   2 +
 8 files changed, 297 insertions(+), 8 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 4f0618f27a..fac0e05dee 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,11 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+
+	bool		ignore_nulls;	/* ignore nulls */
+	int64		*win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -97,6 +102,7 @@ typedef struct WindowStatePerFuncData
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
 
+	bool		ignore_nulls;	/* ignore nulls */
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
 
@@ -2560,14 +2566,14 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/* Look for a previous duplicate window function, which needs the same ignore_nulls value */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2620,6 +2626,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls)
+			{
+				winobj->win_nonnulls = palloc_array(int64, 16);
+				winobj->nonnulls_size = 16;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3306,6 +3319,244 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+static void increment_notnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+							int64,
+							winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+	case WINDOW_SEEK_CURRENT:
+		abs_pos = winstate->currentpos;
+		break;
+	case WINDOW_SEEK_HEAD:
+		abs_pos = 0;
+		break;
+	case WINDOW_SEEK_TAIL:
+		spool_tuples(winstate, -1);
+		abs_pos = winstate->spooled_rows - 1;
+		break;
+	default:
+		elog(ERROR, "unrecognized window seek type: %d", seektype);
+		abs_pos = 0; /* keep compiler quiet */
+		break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i=0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum)0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_notnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum)0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+			int inframe;
+			if (winobj->win_nonnulls[i] < winobj->markpos)
+				continue;
+			if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+				continue;
+
+			inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+			if (inframe <= 0)
+			{
+				if (inframe == -1 && set_mark)
+					WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+				continue;
+			}
+
+			abs_pos = winobj->win_nonnulls[i] + 1;
+			++notnull_offset;
+
+			if (notnull_offset > notnull_relpos)
+			{
+				if (isout)
+				*isout = false;
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+	}
+
+check_frame:
+	do
+	{
+			int inframe;
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			inframe = row_is_in_frame(winstate, abs_pos, slot);
+			if (inframe == -1)
+				goto out_of_frame;
+			else if (inframe == 0)
+				goto advance;
+
+			gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+			if (!gottuple)
+			{
+				if (isout)
+					*isout = true;
+				*isnull = true;
+				return (Datum)0;
+			}
+
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+
+			if (!*isnull)
+			{
+				++notnull_offset;
+				increment_notnulls(winobj, abs_pos);
+			}
+
+advance:
+			abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3340,6 +3591,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+													set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3428,6 +3683,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+												set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index a9c7bc342e..01fd16acf9 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2474,6 +2474,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index acf6cf4866..3992839618 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -633,6 +633,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				opt_frame_clause frame_extent frame_bound
 %type <ival>	opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
+%type <boolean> null_treatment
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
 %type <ival>	generated_when override_kind
@@ -718,7 +719,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -752,8 +753,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
-	ROUTINE ROUTINES ROW ROWS RULE
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	ROLLUP ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
 	SEQUENCE SEQUENCES
@@ -15213,7 +15214,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15246,7 +15247,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -15794,6 +15796,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = true; }
+			| RESPECT_P NULLS_P						{ $$ = false; }
+			| /*EMPTY*/								{ $$ = false; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17111,6 +17119,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17223,6 +17232,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index b3f0b6a137..afa4bcc8d1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	bool		ignore_nulls = (fn ? fn->ignore_nulls : false);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->location = location;
 
 		/*
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 461735e84f..8c77b62263 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10060,7 +10060,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index cc7b32b279..073e2469ba 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -426,6 +426,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	bool		ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index be9c29f0bf..221b5e6218 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -559,6 +559,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls */
+	bool		ignore_nulls;
 	/* token location, or -1 if unknown */
 	int			location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f5b2e61ca5..ed652571e0 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -198,6 +198,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -360,6 +361,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.34.1

From a314d60936b19bd6f0d89876e053ce2eb17b0c09 Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Sat, 29 Apr 2023 23:51:47 +0100
Subject: [PATCH] ignore nulls tests

---
 src/test/regress/expected/window.out | 249 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 120 +++++++++++++
 2 files changed, 369 insertions(+)

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 1d4b78b9b2..f8f59a98d0 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -4850,3 +4850,252 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets;
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 3ab6ac715d..cf47093f34 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1734,3 +1734,123 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets;
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- succeeds
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.34.1

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index fac0e05dee..b8519d9890 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -74,6 +74,7 @@ typedef struct WindowObjectData
 	int64		*win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
 	int			nonnulls_size;	/* track size of the win_nonnulls array */
 	int			nonnulls_len;	/* track length of the win_nonnulls array */
+	WindowFunc	*wfunc;			/* WindowFunc of this function */
 } WindowObjectData;
 
 /*
@@ -2634,6 +2635,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 				winobj->nonnulls_len = 0;
 			}
 
+			winobj->wfunc = wfunc;
+
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
 						  econtext->ecxt_per_query_memory);
@@ -3881,3 +3884,24 @@ WinGetFuncArgCurrent(WindowObject winobj, int argno, bool *isnull)
 	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
 						econtext, isnull);
 }
+
+/*
+ * Error out that this window function cannot have null treatement.
+ */
+void
+ErrorOutNullTreatment(WindowObject winobj)
+{
+	char			*fname;
+
+	Assert(WindowObjectIsValid(winobj));
+
+	if (winobj->wfunc->null_treatment == NULL_TREATMENT_NOT_SET)
+		return;
+
+	fname = get_func_name(winobj->wfunc->winfnoid);
+
+	ereport(ERROR,
+			(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+			 errmsg("window function %s cannot have RESPECT NULLS or IGNORE NULLS",
+					fname)));
+}
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 01fd16acf9..05e64c4569 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2475,6 +2475,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
 				newexpr->ignore_nulls = expr->ignore_nulls;
+				newexpr->null_treatment = expr->null_treatment;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 58c00bfd4f..e131428e85 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -276,6 +276,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 	MergeWhenClause *mergewhen;
 	struct KeyActions *keyactions;
 	struct KeyAction *keyaction;
+	NullTreatment	nulltreatment;
 }
 
 %type <node>	stmt toplevel_stmt schema_stmt routine_body_stmt
@@ -633,7 +634,6 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				opt_frame_clause frame_extent frame_bound
 %type <ival>	opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
-%type <boolean> null_treatment
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
 %type <ival>	generated_when override_kind
@@ -662,6 +662,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 					json_object_constructor_null_clause_opt
 					json_array_constructor_null_clause_opt
 
+%type <nulltreatment>		null_treatment
+
 /*
  * Non-keyword token types.  These are hard-wired into the "flex" lexer.
  * They must be listed first so that their numeric codes do not depend on
@@ -15247,7 +15249,7 @@ func_expr: func_application within_group_clause filter_clause null_treatment ove
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->ignore_nulls = $4;
+					n->null_treatment = $4;
 					n->over = $5;
 					$$ = (Node *) n;
 				}
@@ -15797,9 +15799,9 @@ filter_clause:
  * Window Definitions
  */
 null_treatment:
-			IGNORE_P NULLS_P						{ $$ = true; }
-			| RESPECT_P NULLS_P						{ $$ = false; }
-			| /*EMPTY*/								{ $$ = false; }
+			RESPECT_P NULLS_P						{ $$ = RESPECT_NULLS; }
+			| IGNORE_P NULLS_P						{ $$ = IGNORE_NULLS; }
+			| /*EMPTY*/								{ $$ = NULL_TREATMENT_NOT_SET; }
 		;
 
 window_clause:
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index afa4bcc8d1..63af8ca6aa 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,7 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
-	bool		ignore_nulls = (fn ? fn->ignore_nulls : false);
+	NullTreatment null_treatment = (fn ? fn->null_treatment : NULL_TREATMENT_NOT_SET);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -516,11 +516,12 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
 
-			/* It also can't treat nulls as a window function */
-			if (ignore_nulls)
+			/* Aggregate functions cannot have null treatment clause */
+			if (null_treatment != NULL_TREATMENT_NOT_SET)
 				ereport(ERROR,
 						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 errmsg("aggregate function %s cannot have RESPECT NULLS or IGNORE NULLS",
+								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
 		}
 	}
@@ -842,7 +843,8 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
-		wfunc->ignore_nulls = ignore_nulls;
+		wfunc->null_treatment = null_treatment;
+		wfunc->ignore_nulls = (null_treatment == IGNORE_NULLS);
 		wfunc->location = location;
 
 		/*
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b87a624fb2..297e787927 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -85,6 +85,9 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	/* row_number() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -140,6 +143,9 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	/* rank() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -202,6 +208,9 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	/* dense_rank() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +275,9 @@ window_percent_rank(PG_FUNCTION_ARGS)
 
 	Assert(totalrows > 0);
 
+	/* percent_rank() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -335,6 +347,9 @@ window_cume_dist(PG_FUNCTION_ARGS)
 
 	Assert(totalrows > 0);
 
+	/* cume_dist() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -412,6 +427,9 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	/* ntile() does not support null treatment */
+	ErrorOutNullTreatment(winobj);
+
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 073e2469ba..32fbab46a0 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -432,6 +432,7 @@ typedef struct FuncCall
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
 	bool		func_variadic;	/* last argument was labeled VARIADIC */
 	CoercionForm funcformat;	/* how to display this node */
+	NullTreatment null_treatment;	/* RESPECT_NULLS or IGNORE NULLS */
 	int			location;		/* token location, or -1 if unknown */
 } FuncCall;
 
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 221b5e6218..545b5e5ac8 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -532,6 +532,13 @@ typedef struct GroupingFunc
 	int			location;
 } GroupingFunc;
 
+typedef enum NullTreatment
+{
+	NULL_TREATMENT_NOT_SET = 0,
+	RESPECT_NULLS,
+	IGNORE_NULLS
+} NullTreatment;
+
 /*
  * WindowFunc
  *
@@ -559,7 +566,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
-	/* ignore nulls */
+	/* null treatement */
+	NullTreatment null_treatment pg_node_attr(query_jumble_ignore);
 	bool		ignore_nulls;
 	/* token location, or -1 if unknown */
 	int			location;
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index b8c2c565d1..8a50478ee9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -61,4 +61,6 @@ extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
 extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
 								  bool *isnull);
 
+extern void	ErrorOutNullTreatment(WindowObject winobj);
+
 #endif							/* WINDOWAPI_H */

From 050f4f690d4e3fdfddf2f2aead474a3031f2ebac Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Wed, 4 Sep 2024 10:34:34 +0100
Subject: [PATCH] add ignore_nulls

---
 doc/src/sgml/func.sgml               |  35 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 262 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  18 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |   2 +
 src/include/parser/kwlist.h          |   2 +
 src/test/regress/expected/window.out | 249 +++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 120 ++++++++++++
 13 files changed, 691 insertions(+), 27 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 461fc3f..3ea41d9 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23172,7 +23172,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23197,7 +23197,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23220,7 +23220,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23234,7 +23234,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23248,7 +23248,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23297,18 +23297,23 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 4dfbbd0..b66fcaa 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index c002f37..3187898 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 3221fa1..00fd72e 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	bool		ignore_nulls;	/* ignore nulls */
+	int64		*win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -96,6 +100,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	bool		ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -2563,14 +2568,14 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/* Look for a previous duplicate window function, which needs the same ignore_nulls value */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2623,6 +2628,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls)
+			{
+				winobj->win_nonnulls = palloc_array(int64, 16);
+				winobj->nonnulls_size = 16;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3289,6 +3301,244 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+static void increment_notnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+							int64,
+							winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+	case WINDOW_SEEK_CURRENT:
+		abs_pos = winstate->currentpos;
+		break;
+	case WINDOW_SEEK_HEAD:
+		abs_pos = 0;
+		break;
+	case WINDOW_SEEK_TAIL:
+		spool_tuples(winstate, -1);
+		abs_pos = winstate->spooled_rows - 1;
+		break;
+	default:
+		elog(ERROR, "unrecognized window seek type: %d", seektype);
+		abs_pos = 0; /* keep compiler quiet */
+		break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i=0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum)0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_notnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum)0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+			int inframe;
+			if (winobj->win_nonnulls[i] < winobj->markpos)
+				continue;
+			if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+				continue;
+
+			inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+			if (inframe <= 0)
+			{
+				if (inframe == -1 && set_mark)
+					WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+				continue;
+			}
+
+			abs_pos = winobj->win_nonnulls[i] + 1;
+			++notnull_offset;
+
+			if (notnull_offset > notnull_relpos)
+			{
+				if (isout)
+				*isout = false;
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+	}
+
+check_frame:
+	do
+	{
+			int inframe;
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			inframe = row_is_in_frame(winstate, abs_pos, slot);
+			if (inframe == -1)
+				goto out_of_frame;
+			else if (inframe == 0)
+				goto advance;
+
+			gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+			if (!gottuple)
+			{
+				if (isout)
+					*isout = true;
+				*isnull = true;
+				return (Datum)0;
+			}
+
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+
+			if (!*isnull)
+			{
+				++notnull_offset;
+				increment_notnulls(winobj, abs_pos);
+			}
+
+advance:
+			abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3323,6 +3573,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+													set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3411,6 +3665,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+												set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index b4e085e..d3a5596 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 84cef57..d4d59d4 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -638,6 +638,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 				opt_frame_clause frame_extent frame_bound
 %type <ival>	opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
+%type <boolean> null_treatment
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
 %type <ival>	generated_when override_kind
@@ -734,7 +735,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -769,7 +770,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15546,7 +15547,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15579,7 +15580,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16175,6 +16177,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = true; }
+			| RESPECT_P NULLS_P						{ $$ = false; }
+			| /*EMPTY*/								{ $$ = false; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17609,6 +17617,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17725,6 +17734,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9b23344..e692931 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	bool		ignore_nulls = (fn ? fn->ignore_nulls : false);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index b31be31..0851333 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10752,7 +10752,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 124d853..7eaf2bc 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -428,6 +428,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	bool		ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index ea47652..89d77c0 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -583,6 +583,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls */
+	bool		ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f865907..70a6824 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -201,6 +201,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -375,6 +376,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 8b447aa..bebee66 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5393,3 +5393,252 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets;
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6de5493..73f8261 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1951,3 +1951,123 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets;
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- succeeds
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.34.1

From c6c3b228d70bc3458056a9d2ecba5b75876943d9 Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Sun, 8 Sep 2024 15:21:13 +0100
Subject: [PATCH] add ignore_nulls

---
 doc/src/sgml/func.sgml               |  35 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 262 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |   2 +
 src/include/parser/kwlist.h          |   2 +
 src/test/regress/expected/window.out | 238 ++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 120 ++++++++++++
 13 files changed, 680 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 461fc3f..4d5aa78 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23172,7 +23172,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23197,7 +23197,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23220,7 +23220,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23234,7 +23234,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23248,7 +23248,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23297,18 +23297,23 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 4dfbbd0..b66fcaa 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index c002f37..3187898 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 51a6708..7e310b6 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
+	int64		*win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -96,6 +100,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -2620,14 +2625,14 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/* Look for a previous duplicate window function, which needs the same ignore_nulls value */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2680,6 +2685,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == 1)
+			{
+				winobj->win_nonnulls = palloc_array(int64, 16);
+				winobj->nonnulls_size = 16;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3355,6 +3367,244 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+static void increment_notnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+							int64,
+							winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+	case WINDOW_SEEK_CURRENT:
+		abs_pos = winstate->currentpos;
+		break;
+	case WINDOW_SEEK_HEAD:
+		abs_pos = 0;
+		break;
+	case WINDOW_SEEK_TAIL:
+		spool_tuples(winstate, -1);
+		abs_pos = winstate->spooled_rows - 1;
+		break;
+	default:
+		elog(ERROR, "unrecognized window seek type: %d", seektype);
+		abs_pos = 0; /* keep compiler quiet */
+		break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i=0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum)0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_notnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+						int relpos, int seektype, bool set_mark, bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum)0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+			int inframe;
+			if (winobj->win_nonnulls[i] < winobj->markpos)
+				continue;
+			if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+				continue;
+
+			inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+			if (inframe <= 0)
+			{
+				if (inframe == -1 && set_mark)
+					WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+				continue;
+			}
+
+			abs_pos = winobj->win_nonnulls[i] + 1;
+			++notnull_offset;
+
+			if (notnull_offset > notnull_relpos)
+			{
+				if (isout)
+				*isout = false;
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+	}
+
+check_frame:
+	do
+	{
+			int inframe;
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			inframe = row_is_in_frame(winstate, abs_pos, slot);
+			if (inframe == -1)
+				goto out_of_frame;
+			else if (inframe == 0)
+				goto advance;
+
+			gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+			if (!gottuple)
+			{
+				if (isout)
+					*isout = true;
+				*isnull = true;
+				return (Datum)0;
+			}
+
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+
+			if (!*isnull)
+			{
+				++notnull_offset;
+				increment_notnulls(winobj, abs_pos);
+			}
+
+advance:
+			abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3389,6 +3639,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == 1 && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+													set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3477,6 +3731,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == 1)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+												set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index b4e085e..d3a5596 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 84cef57..8cff433 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -636,7 +636,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -734,7 +734,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -769,7 +769,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15546,7 +15546,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15579,7 +15579,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16175,6 +16176,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = +1; }
+			| RESPECT_P NULLS_P						{ $$ = -1; }
+			| /*EMPTY*/								{ $$ = 0; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17609,6 +17616,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17725,6 +17733,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 9b23344..9108932 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index cd9c3ed..16c7088 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -10752,7 +10752,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == 1)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 124d853..82dc2dc 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -428,6 +428,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index ea47652..f336e67 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -583,6 +583,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. 1 for IGNORE, -1 for RESPECT, 0 if unspecified */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index f865907..70a6824 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -201,6 +201,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -375,6 +376,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 8b447aa..6d16f1f 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5393,3 +5393,241 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6de5493..b4bc2db 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1951,3 +1951,123 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- regular aggregate
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.34.1

From 09b27d27d0904100a35548a938d8d20c8d277cda Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Fri, 17 Jan 2025 09:17:44 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 282 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |  36 ++++
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |   2 +
 src/include/parser/kwlist.h          |   2 +
 src/test/regress/expected/window.out | 261 +++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 123 ++++++++++++
 13 files changed, 756 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 47370e581a..f86b715ba5 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23252,7 +23252,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23277,7 +23277,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23300,7 +23300,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23314,7 +23314,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23328,7 +23328,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23377,18 +23377,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..e1117857dc 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -96,6 +100,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -2619,14 +2624,14 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/* Look for a previous duplicate window function, which needs the same ignore_nulls value */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2684,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == 1)
+			{
+				winobj->win_nonnulls = palloc_array(int64, 16);
+				winobj->nonnulls_size = 16;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3354,6 +3366,264 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+							int64,
+							winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+	case WINDOW_SEEK_CURRENT:
+		abs_pos = winstate->currentpos;
+		break;
+	case WINDOW_SEEK_HEAD:
+		abs_pos = 0;
+		break;
+	case WINDOW_SEEK_TAIL:
+		spool_tuples(winstate, -1);
+		abs_pos = winstate->spooled_rows - 1;
+		break;
+	default:
+		elog(ERROR, "unrecognized window seek type: %d", seektype);
+		abs_pos = 0; /* keep compiler quiet */
+		break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i=0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum)0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout) {
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum)0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+			int inframe;
+			if (winobj->win_nonnulls[i] < winobj->markpos)
+				continue;
+			if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+				continue;
+
+			inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+			if (inframe <= 0)
+			{
+				if (inframe == -1 && set_mark)
+					WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+				continue;
+			}
+
+			abs_pos = winobj->win_nonnulls[i] + 1;
+			++notnull_offset;
+
+			if (notnull_offset > notnull_relpos)
+			{
+				if (isout)
+				*isout = false;
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+	}
+
+check_frame:
+	do
+	{
+			int inframe;
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			inframe = row_is_in_frame(winstate, abs_pos, slot);
+			if (inframe == -1)
+				goto out_of_frame;
+			else if (inframe == 0)
+				goto advance;
+
+			gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+			if (!gottuple)
+			{
+				if (isout)
+					*isout = true;
+				*isnull = true;
+				return (Datum)0;
+			}
+
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+
+			if (!*isnull)
+			{
+				++notnull_offset;
+				increment_nonnulls(winobj, abs_pos);
+			}
+
+advance:
+			abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3388,6 +3658,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == 1 && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+													set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3750,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == 1)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+												set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c40..5dac1223d1 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15723,7 +15723,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15756,7 +15756,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16352,6 +16353,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = +1; }
+			| RESPECT_P NULLS_P						{ $$ = -1; }
+			| /*EMPTY*/								{ $$ = 0; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17789,6 +17796,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17906,6 +17914,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..ca663e1bfa 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -31,6 +31,7 @@
 #include "parser/parse_target.h"
 #include "parser/parse_type.h"
 #include "utils/builtins.h"
+#include "utils/fmgroids.h"
 #include "utils/lsyscache.h"
 #include "utils/syscache.h"
 
@@ -98,6 +99,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +516,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != 0)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -534,6 +543,32 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("window function %s cannot have WITHIN GROUP",
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
+		/* Null treatment is currently limited to specific functions */
+		if (ignore_nulls != 0)
+		{
+			switch (funcid)
+			{
+				case F_LAG_ANYELEMENT:
+				case F_LAG_ANYELEMENT_INT4:
+				case F_LAG_ANYCOMPATIBLE_INT4_ANYCOMPATIBLE:
+				case F_LEAD_ANYELEMENT:
+				case F_LEAD_ANYELEMENT_INT4:
+				case F_LEAD_ANYCOMPATIBLE_INT4_ANYCOMPATIBLE:
+				case F_FIRST_VALUE:
+				case F_LAST_VALUE:
+				case F_NTH_VALUE:
+					/* valid function */
+					break;
+				default:
+					ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("window function %s cannot have a RESPECT/IGNORE NULLS clause",
+								NameListToString(funcname)),
+						 parser_errposition(pstate, location)));
+					break;
+
+			}
+		}
 	}
 	else if (fdresult == FUNCDETAIL_COERCION)
 	{
@@ -834,6 +869,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..072fe5a755 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == 1)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ffe155ee20..51e2ea19c5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 59e7bb26bb..6b2eb7872e 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -599,6 +599,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. 1 for IGNORE, -1 for RESPECT, 0 if unspecified */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index cf2917ad07..4d662b5276 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..16285c812a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,264 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  window function row_number cannot have a RESPECT/IGNORE NULLS clause
+LINE 1: SELECT row_number() RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  window function row_number cannot have a RESPECT/IGNORE NULLS clause
+LINE 1: SELECT row_number() IGNORE NULLS OVER () FROM planets;
+               ^
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..236a1630cf 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,126 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e1117857dc0..520e7e1bfcb 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2624,7 +2624,10 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function, which needs the same ignore_nulls value */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
@@ -3379,8 +3382,8 @@ increment_nonnulls(WindowObject winobj, int64 pos)
 		winobj->nonnulls_size *= 2;
 		winobj->win_nonnulls =
 			repalloc_array(winobj->win_nonnulls,
-							int64,
-							winobj->nonnulls_size);
+						   int64,
+						   winobj->nonnulls_size);
 	}
 	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
 	winobj->nonnulls_len++;
@@ -3394,7 +3397,8 @@ increment_nonnulls(WindowObject winobj, int64 pos)
 static Datum
 ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
 								  int relpos, int seektype, bool set_mark,
-								  bool *isnull, bool *isout) {
+								  bool *isnull, bool *isout)
+{
 	WindowAggState *winstate;
 	ExprContext *econtext;
 	TupleTableSlot *slot;
@@ -3416,27 +3420,27 @@ ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
 
 	switch (seektype)
 	{
-	case WINDOW_SEEK_CURRENT:
-		abs_pos = winstate->currentpos;
-		break;
-	case WINDOW_SEEK_HEAD:
-		abs_pos = 0;
-		break;
-	case WINDOW_SEEK_TAIL:
-		spool_tuples(winstate, -1);
-		abs_pos = winstate->spooled_rows - 1;
-		break;
-	default:
-		elog(ERROR, "unrecognized window seek type: %d", seektype);
-		abs_pos = 0; /* keep compiler quiet */
-		break;
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
 	}
 
 	if (forward == -1)
 		goto check_partition;
 
 	/* if we're moving forward, store previous rows */
-	for (i=0; i < winobj->nonnulls_len; ++i)
+	for (i = 0; i < winobj->nonnulls_len; ++i)
 	{
 		if (winobj->win_nonnulls[i] > abs_pos)
 		{
@@ -3448,7 +3452,7 @@ ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
 					*isout = false;
 				window_gettupleslot(winobj, abs_pos, slot);
 				econtext->ecxt_outertuple = slot;
-				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
 									econtext, isnull);
 			}
 		}
@@ -3465,13 +3469,13 @@ check_partition:
 			if (isout)
 				*isout = true;
 			*isnull = true;
-			return (Datum)0;
+			return (Datum) 0;
 		}
 
 		if (isout)
 			*isout = false;
 		econtext->ecxt_outertuple = slot;
-		datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
 							 econtext, isnull);
 
 		if (!*isnull)
@@ -3494,7 +3498,8 @@ check_partition:
 static Datum
 ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 							  int relpos, int seektype, bool set_mark,
-							  bool *isnull, bool *isout) {
+							  bool *isnull, bool *isout)
+{
 	WindowAggState *winstate;
 	ExprContext *econtext;
 	TupleTableSlot *slot;
@@ -3511,7 +3516,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 	winstate = winobj->winstate;
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
-	datum = (Datum)0;
+	datum = (Datum) 0;
 	notnull_offset = 0;
 	notnull_relpos = abs(relpos);
 
@@ -3549,70 +3554,72 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 	 */
 	for (i = 0; i < winobj->nonnulls_len; ++i)
 	{
-			int inframe;
-			if (winobj->win_nonnulls[i] < winobj->markpos)
-				continue;
-			if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
-				continue;
+		int			inframe;
 
-			inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
-			if (inframe <= 0)
-			{
-				if (inframe == -1 && set_mark)
-					WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
-				continue;
-			}
+		if (winobj->win_nonnulls[i] < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+			continue;
 
-			abs_pos = winobj->win_nonnulls[i] + 1;
-			++notnull_offset;
+		inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+		if (inframe <= 0)
+		{
+			if (inframe == -1 && set_mark)
+				WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+			continue;
+		}
 
-			if (notnull_offset > notnull_relpos)
-			{
-				if (isout)
+		abs_pos = winobj->win_nonnulls[i] + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
 				*isout = false;
-				econtext->ecxt_outertuple = slot;
-				return ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
-									econtext, isnull);
-			}
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
 	}
 
 check_frame:
 	do
 	{
-			int inframe;
-			if (!window_gettupleslot(winobj, abs_pos, slot))
-				goto out_of_frame;
+		int			inframe;
 
-			inframe = row_is_in_frame(winstate, abs_pos, slot);
-			if (inframe == -1)
-				goto out_of_frame;
-			else if (inframe == 0)
-				goto advance;
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
 
-			gottuple = window_gettupleslot(winobj, abs_pos, slot);
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
 
-			if (!gottuple)
-			{
-				if (isout)
-					*isout = true;
-				*isnull = true;
-				return (Datum)0;
-			}
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
 
+		if (!gottuple)
+		{
 			if (isout)
-				*isout = false;
-			econtext->ecxt_outertuple = slot;
-			datum = ExecEvalExpr((ExprState *)list_nth(winobj->argstates, argno),
-								 econtext, isnull);
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
 
-			if (!*isnull)
-			{
-				++notnull_offset;
-				increment_nonnulls(winobj, abs_pos);
-			}
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
 
 advance:
-			abs_pos += forward;
+		abs_pos += forward;
 	} while (notnull_offset <= notnull_relpos);
 
 	return datum;
@@ -3660,7 +3667,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 
 	if (winobj->ignore_nulls == 1 && relpos != 0)
 		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
-													set_mark, isnull, isout);
+												 set_mark, isnull, isout);
 
 	switch (seektype)
 	{
@@ -3752,7 +3759,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 
 	if (winobj->ignore_nulls == 1)
 		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
-												set_mark, isnull, isout);
+											 set_mark, isnull, isout);
 
 	switch (seektype)
 	{

From 892e82cb0e08f6736056593076a976e765822cfd Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Fri, 17 Jan 2025 09:17:44 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 320 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  14 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 257 +++++++++++++++++++++
 src/test/regress/sql/window.sql      | 123 ++++++++++
 15 files changed, 789 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 47370e581a..f86b715ba5 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23252,7 +23252,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23277,7 +23277,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23300,7 +23300,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23314,7 +23314,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23328,7 +23328,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23377,18 +23377,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..74c99e7cd7 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -96,6 +100,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -2619,14 +2624,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2687,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3220,6 +3229,43 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and initialize non-nulls array
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to initialize the
+ * win_nonnulls array.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		winobj->ignore_nulls = IGNORE_NULLS;
+		winobj->win_nonnulls = palloc_array(int64, 16);
+		winobj->nonnulls_size = 16;
+		winobj->nonnulls_len = 0;
+	}
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3354,6 +3400,268 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+						   int64,
+						   winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int			inframe;
+
+		if (winobj->win_nonnulls[i] < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+			continue;
+
+		inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+		if (inframe <= 0)
+		{
+			if (inframe == -1 && set_mark)
+				WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+			continue;
+		}
+
+		abs_pos = winobj->win_nonnulls[i] + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
+	}
+
+check_frame:
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3388,6 +3696,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3788,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c40..7ca616e8f7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15723,7 +15723,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15756,7 +15756,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16352,6 +16353,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17789,6 +17796,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17906,6 +17914,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..4c0837cb2a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ffe155ee20..51e2ea19c5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 59e7bb26bb..cc4221ab0d 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -576,6 +576,18 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE
+ * or PARSER_RESPECT. PARSER_IGNORE_NULLS is then converted to IGNORE_NULLS
+ * if the window function allows the null treatment clause.
+ */
+#define IGNORE_NULLS 4
+#define RESPECT_NULLS 3
+#define PARSER_IGNORE_NULLS 2
+#define PARSER_RESPECT_NULLS 1
+#define NO_NULLTREATMENT 0
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -599,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. one of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index cf2917ad07..4d662b5276 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..99cfc27e2c 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,260 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..236a1630cf 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,126 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 88),
+  ('venus', 224),
+  ('earth', NULL),
+  ('mars', NULL),
+  ('jupiter', 4332),
+  ('saturn', 24491),
+  ('uranus', NULL),
+  ('neptune', 60182),
+  ('pluto', 90560),
+  ('xyzzy', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From 5268754b33103fefc511b57ec546103899f70dbe Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Thu, 23 Jan 2025 20:11:17 +0000
Subject: [PATCH] :ignore nulls

---
 doc/src/sgml/func.sgml               |  38 +--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 332 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  14 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 284 +++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 137 +++++++++++
 15 files changed, 842 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 5678e7621a..07018a5070 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23265,7 +23265,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23290,7 +23290,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23313,7 +23313,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23327,7 +23327,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23341,7 +23341,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23390,18 +23390,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..d93a44633e 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
 /*
@@ -96,6 +100,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -1263,6 +1268,15 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+
+			/* reallocate null check */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+			{
+				perfuncstate->winobj->win_nonnulls = palloc_array(int64, 16);
+				perfuncstate->winobj->nonnulls_size = 16;
+				perfuncstate->winobj->nonnulls_len = 0;
+			}
 		}
 	}
 
@@ -1383,7 +1397,9 @@ release_partition(WindowAggState *winstate)
 
 		/* Release any partition-local state of this window function */
 		if (perfuncstate->winobj)
+		{
 			perfuncstate->winobj->localmem = NULL;
+		}
 	}
 
 	/*
@@ -2619,14 +2635,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2698,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+			{
+				winobj->win_nonnulls = palloc_array(int64, 16);
+				winobj->nonnulls_size = 16;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3220,6 +3246,38 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3354,6 +3412,268 @@ WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2)
 	return res;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+						   int64,
+						   winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		if (winobj->win_nonnulls[i] > abs_pos)
+		{
+			abs_pos = winobj->win_nonnulls[i];
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int			inframe;
+
+		if (winobj->win_nonnulls[i] < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, winobj->win_nonnulls[i], slot))
+			continue;
+
+		inframe = row_is_in_frame(winstate, winobj->win_nonnulls[i], slot);
+		if (inframe <= 0)
+		{
+			if (inframe == -1 && set_mark)
+				WinSetMarkPosition(winobj, winobj->win_nonnulls[i]);
+			continue;
+		}
+
+		abs_pos = winobj->win_nonnulls[i] + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
+	}
+
+check_frame:
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 /*
  * WinGetFuncArgInPartition
  *		Evaluate a window function's argument expression on a specified
@@ -3388,6 +3708,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3800,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c40..7ca616e8f7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15723,7 +15723,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15756,7 +15756,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16352,6 +16353,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17789,6 +17796,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17906,6 +17914,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..4c0837cb2a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ffe155ee20..51e2ea19c5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 59e7bb26bb..cc4221ab0d 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -576,6 +576,18 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE
+ * or PARSER_RESPECT. PARSER_IGNORE_NULLS is then converted to IGNORE_NULLS
+ * if the window function allows the null treatment clause.
+ */
+#define IGNORE_NULLS 4
+#define RESPECT_NULLS 3
+#define PARSER_IGNORE_NULLS 2
+#define PARSER_RESPECT_NULLS 1
+#define NO_NULLTREATMENT 0
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -599,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. one of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index cf2917ad07..4d662b5276 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..361596a526 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,287 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..3bdd2d66e2 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,140 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From 6822d04516fedbe2ea6e939fcb44a36e5e85d26b Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Mon, 27 Jan 2025 15:41:40 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 325 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 284 +++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 137 +++++++++++
 15 files changed, 834 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7efc81936a..79022c9d45 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23303,7 +23303,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23328,7 +23328,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23351,7 +23351,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23365,7 +23365,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23379,7 +23379,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23428,18 +23428,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..c18910f21d 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,8 +69,15 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			ignore_nulls;	/* ignore nulls */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
+/* Initial size of the win_nonnulls array */
+#define WIN_NONNULLS_SIZE		16
+
 /*
  * We have one WindowStatePerFunc struct for each window function and
  * window aggregate handled by this node.
@@ -96,6 +103,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +206,15 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static void increment_nonnulls(WindowObject winobj, int64 pos);
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool set_mark,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1280,10 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null array length */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				perfuncstate->winobj->nonnulls_len = 0;
 		}
 	}
 
@@ -2619,14 +2640,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2703,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+			{
+				winobj->win_nonnulls = palloc_array(int64, WIN_NONNULLS_SIZE);
+				winobj->nonnulls_size = WIN_NONNULLS_SIZE;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3245,294 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+						   int64,
+						   winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull > abs_pos)
+		{
+			abs_pos = nonnull;
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int			inframe;
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, nonnull, slot))
+			continue;
+
+		inframe = row_is_in_frame(winstate, nonnull, slot);
+		if (inframe <= 0)
+			continue;
+
+		abs_pos = nonnull + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
+	}
+
+check_frame:
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3701,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3793,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c40..7ca616e8f7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15723,7 +15723,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15756,7 +15756,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16352,6 +16353,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17789,6 +17796,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17906,6 +17914,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..4c0837cb2a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ffe155ee20..51e2ea19c5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 59e7bb26bb..c633250cce 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -576,6 +576,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -599,6 +610,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index cf2917ad07..4d662b5276 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..361596a526 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,287 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..3bdd2d66e2 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,140 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From 37f891a6fb3dc64b7f091f87bc000ceedfca98f5 Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Mon, 3 Feb 2025 19:02:15 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 328 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 ++++++++++++
 15 files changed, 874 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7efc81936a..79022c9d45 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23303,7 +23303,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23328,7 +23328,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23351,7 +23351,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23365,7 +23365,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23379,7 +23379,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23428,18 +23428,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..ec69831252 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,8 +69,15 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			ignore_nulls;	/* ignore nulls */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
+/* Initial size of the win_nonnulls array */
+#define WIN_NONNULLS_SIZE		16
+
 /*
  * We have one WindowStatePerFunc struct for each window function and
  * window aggregate handled by this node.
@@ -96,6 +103,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +206,15 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static void increment_nonnulls(WindowObject winobj, int64 pos);
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool set_mark,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1280,10 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null array length */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				perfuncstate->winobj->nonnulls_len = 0;
 		}
 	}
 
@@ -2619,14 +2640,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2703,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+			{
+				winobj->win_nonnulls = palloc_array(int64, WIN_NONNULLS_SIZE);
+				winobj->nonnulls_size = WIN_NONNULLS_SIZE;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3245,297 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+						   int64,
+						   winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull > abs_pos)
+		{
+			abs_pos = nonnull;
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			forward = 1;
+			if (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
+				goto check_frame;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode without an
+	 * exclusion clause.
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int			inframe;
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, nonnull, slot))
+			continue;
+
+		inframe = row_is_in_frame(winstate, nonnull, slot);
+		if (inframe <= 0)
+			continue;
+
+		abs_pos = nonnull + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
+	}
+
+check_frame:
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3704,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3796,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c40..7ca616e8f7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15723,7 +15723,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15756,7 +15756,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16352,6 +16353,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17789,6 +17796,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17906,6 +17914,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..4c0837cb2a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ffe155ee20..51e2ea19c5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 839e71d52f..82f812fbd0 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index cf2917ad07..4d662b5276 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..f596dfff6e 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..1f8c866943 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From d8f1e28411b8cea52e1c66697125c86b511c08a6 Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Tue, 18 Feb 2025 13:06:29 +0000
Subject: [PATCH] ignore

---
 doc/src/sgml/func.sgml               |  38 +--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 333 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 ++++++++++++
 15 files changed, 879 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7efc81936a..79022c9d45 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23303,7 +23303,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23328,7 +23328,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23351,7 +23351,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23365,7 +23365,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23379,7 +23379,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23428,18 +23428,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..3d7a812168 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,8 +69,15 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int64	   *win_nonnulls;	/* tracks non-nulls in ignore nulls mode */
+	int			ignore_nulls;	/* ignore nulls */
+	int			nonnulls_size;	/* track size of the win_nonnulls array */
+	int			nonnulls_len;	/* track length of the win_nonnulls array */
 } WindowObjectData;
 
+/* Initial size of the win_nonnulls array */
+#define WIN_NONNULLS_SIZE		16
+
 /*
  * We have one WindowStatePerFunc struct for each window function and
  * window aggregate handled by this node.
@@ -96,6 +103,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +206,15 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static void increment_nonnulls(WindowObject winobj, int64 pos);
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool set_mark,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1280,10 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null array length */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				perfuncstate->winobj->nonnulls_len = 0;
 		}
 	}
 
@@ -2619,14 +2640,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2703,13 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+			{
+				winobj->win_nonnulls = palloc_array(int64, WIN_NONNULLS_SIZE);
+				winobj->nonnulls_size = WIN_NONNULLS_SIZE;
+				winobj->nonnulls_len = 0;
+			}
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3245,302 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * increment_nonnulls
+ * For IGNORE NULLS, add the current position to the nonnulls array,
+ * doubling the array capacity if needed.
+ */
+static void
+increment_nonnulls(WindowObject winobj, int64 pos)
+{
+	if (winobj->nonnulls_len == winobj->nonnulls_size)
+	{
+		winobj->nonnulls_size *= 2;
+		winobj->win_nonnulls =
+			repalloc_array(winobj->win_nonnulls,
+						   int64,
+						   winobj->nonnulls_size);
+	}
+	winobj->win_nonnulls[winobj->nonnulls_len] = pos;
+	winobj->nonnulls_len++;
+}
+
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool set_mark,
+								  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	if (forward == -1)
+		goto check_partition;
+
+	/* if we're moving forward, store previous rows */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull > abs_pos)
+		{
+			abs_pos = nonnull;
+			++notnull_offset;
+			if (notnull_offset == notnull_relpos)
+			{
+				if (isout)
+					*isout = false;
+				window_gettupleslot(winobj, abs_pos, slot);
+				econtext->ecxt_outertuple = slot;
+				return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+									econtext, isnull);
+			}
+		}
+	}
+
+check_partition:
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			i;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			if (winstate->frameOptions & FRAMEOPTION_EXCLUSION)
+				goto check_frame;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0; /* keep compiler quiet */
+			forward = -1;
+			goto check_frame;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Store previous rows. Only possible in SEEK_HEAD mode without an
+	 * exclusion clause.
+	 */
+	for (i = 0; i < winobj->nonnulls_len; ++i)
+	{
+		int			inframe;
+		int64	nonnull = winobj->win_nonnulls[i];
+
+		if (nonnull < winobj->markpos)
+			continue;
+		if (!window_gettupleslot(winobj, nonnull, slot))
+			continue;
+
+		inframe = row_is_in_frame(winstate, nonnull, slot);
+		if (inframe <= 0)
+			continue;
+
+		abs_pos = nonnull + 1;
+		++notnull_offset;
+
+		if (notnull_offset > notnull_relpos)
+		{
+			if (isout)
+				*isout = false;
+			econtext->ecxt_outertuple = slot;
+			return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+								econtext, isnull);
+		}
+	}
+
+check_frame:
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+		{
+			++notnull_offset;
+			increment_nonnulls(winobj, abs_pos);
+		}
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3709,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3801,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d3887628d4..2eac4d27e7 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15730,7 +15730,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15763,7 +15763,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16359,6 +16360,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17796,6 +17803,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17913,6 +17921,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 54dad97555..4c0837cb2a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11021,7 +11021,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 8dd421fa0e..2fcdbf61d2 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 839e71d52f..82f812fbd0 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 40cf090ce6..3ba00a39e5 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..f596dfff6e 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..1f8c866943 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From a952152474a310f9c62928f9c4fc751a1ca5366a Mon Sep 17 00:00:00 2001
From: Oliver Ford <ojford@gmail.com>
Date: Thu, 6 Mar 2025 08:12:45 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 225 ++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   4 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++++
 15 files changed, 771 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index f97f0ce570..e2a56b6c91 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23425,7 +23425,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23450,7 +23450,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23473,7 +23473,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23487,7 +23487,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23501,7 +23501,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23550,18 +23550,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d6..237d7306fe 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57..46a8959cb2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5..149333bb68 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +97,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +200,13 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -2619,14 +2628,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2691,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3227,212 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool *isnull,
+								  bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1 + relpos;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+	} while (notnull_offset < notnull_relpos);
+
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0; /* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3601,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3693,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47..e7091d7468 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 271ae26cba..19b1e61d10 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15758,7 +15758,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15791,7 +15791,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16387,6 +16388,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17824,6 +17831,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17941,6 +17949,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232..3772c514b1 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d11a8a20ee..63e9a347fe 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11028,7 +11028,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a..969f02aa59 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 23c9e3c5ab..b13a7bfe67 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d0576da3e2..6508161640 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 40cf090ce6..3ba00a39e5 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b..b1595d308d 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,6 +41,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df2..f596dfff6e 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070..1f8c866943 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.47.2

From cf678af9b4ebf4f31af5c3e9b0632b2c777a9ad1 Mon Sep 17 00:00:00 2001
From: Oliver Ford <oliver.f@argodevops.co.uk>
Date: Sun, 9 Mar 2025 16:39:26 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 225 ++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++++
 15 files changed, 773 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 51dd8ad6571..d8cf8b039d5 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23442,7 +23442,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23467,7 +23467,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23490,7 +23490,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23504,7 +23504,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23518,7 +23518,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23567,18 +23567,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57b..46a8959cb2f 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..149333bb687 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +97,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +200,13 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -2619,14 +2628,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2691,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3227,212 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool *isnull,
+								  bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1 + relpos;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+	} while (notnull_offset < notnull_relpos);
+
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0; /* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3601,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3693,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47f..e7091d7468c 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 271ae26cbaf..19b1e61d10b 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15758,7 +15758,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15791,7 +15791,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16387,6 +16388,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17824,6 +17831,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17941,6 +17949,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index d11a8a20eea..63e9a347fed 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11028,7 +11028,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	foreach(l, context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 23c9e3c5abf..b13a7bfe674 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d0576da3e25..65081616402 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 40cf090ce61..3ba00a39e5d 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 23d1463df22..f596dfff6ef 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5403,3 +5403,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From bf4ddaa83c1004a96471106babf6a06022c4228c Mon Sep 17 00:00:00 2001
From: Oliver Ford <oliver.f@argodevops.co.uk>
Date: Wed, 12 Mar 2025 13:34:30 +0000
Subject: [PATCH] ignore nulls

---
 doc/src/sgml/func.sgml               |  38 ++--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 225 ++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 ++
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++++
 15 files changed, 773 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 51dd8ad6571..d8cf8b039d5 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23442,7 +23442,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23467,7 +23467,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23490,7 +23490,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23504,7 +23504,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23518,7 +23518,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23567,18 +23567,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57b..46a8959cb2f 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..149333bb687 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +97,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +200,13 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark,  bool *isnull,
+										   bool *isout);
 
 /*
  * initialize_windowaggregate
@@ -2619,14 +2628,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2691,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3227,212 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull value in the partition, moving forward or backward
+ * until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool *isnull,
+								  bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1 + relpos;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+	} while (notnull_offset < notnull_relpos);
+
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward or backward
+ * until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0; /* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		int			inframe;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3601,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(winobj, argno, relpos, seektype,
+												 isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3693,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 43dfecfb47f..e7091d7468c 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2570,6 +2570,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 271ae26cbaf..19b1e61d10b 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15758,7 +15758,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15791,7 +15791,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16387,6 +16388,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17824,6 +17831,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17941,6 +17949,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9e90acedb91..ac97a35ad47 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11080,7 +11080,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 23c9e3c5abf..b13a7bfe674 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -439,6 +439,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index d0576da3e25..65081616402 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 40cf090ce61..3ba00a39e5d 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -377,6 +378,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From f1da51ab3c5b2eb5fa07c762ba6e4ccaf30ad208 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 11 Jun 2025 20:47:54 +0900
Subject: [PATCH v12] Add IGNORE NULLS/RESPECT NULLS option to Window
 functions.

Add IGNORE NULLS/RESPECT NULLS option to lead, lag, first_value,
last_value and nth_value.
---
 doc/src/sgml/func.sgml               |  38 +--
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 359 ++++++++++++++++++++++++++-
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 +
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++
 15 files changed, 907 insertions(+), 28 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index c67688cbf5f..fd9bdf2f73c 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23533,7 +23533,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23558,7 +23558,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23581,7 +23581,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23595,7 +23595,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23609,7 +23609,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23658,18 +23658,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..11e0a496e25 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,9 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +99,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +202,35 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+											   int relpos, int seektype,
+											   bool *isnull, bool *isout);
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info map consists of 2-bits array:
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1296,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -2619,14 +2657,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2720,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3257,235 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * ignorenulls_getfuncarginpartition
+ * For IGNORE NULLS, get the next nonnull * value in the partition, moving
+ * forward or backward until we find a value or reach the partition's end.
+ */
+static Datum
+ignorenulls_getfuncarginpartition(WindowObject winobj, int argno,
+								  int relpos, int seektype, bool *isnull,
+								  bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	bool		gottuple;
+	int64		abs_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	forward = relpos > 0 ? 1 : -1;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			abs_pos = winstate->currentpos;
+			break;
+		case WINDOW_SEEK_HEAD:
+			abs_pos = 0;
+			break;
+		case WINDOW_SEEK_TAIL:
+			spool_tuples(winstate, -1);
+			abs_pos = winstate->spooled_rows - 1 + relpos;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = 0;		/* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		abs_pos += forward;
+		gottuple = window_gettupleslot(winobj, abs_pos, slot);
+
+		if (!gottuple)
+		{
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			return (Datum) 0;
+		}
+
+		if (isout)
+			*isout = false;
+		econtext->ecxt_outertuple = slot;
+		datum = ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+							 econtext, isnull);
+
+		if (!*isnull)
+			++notnull_offset;
+	} while (notnull_offset < notnull_relpos);
+
+	return datum;
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		int			inframe;
+		int			v;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3388,6 +3654,10 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+		return ignorenulls_getfuncarginpartition(
+												 winobj, argno, relpos, seektype, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3476,6 +3746,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3670,3 +3944,84 @@ WinGetFuncArgCurrent(WindowObject winobj, int argno, bool *isnull)
 	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
 						econtext, isnull);
 }
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 26a3e050086..9705c8ef2e8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2572,6 +2572,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 0b5652071d1..84d92332053 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15760,7 +15760,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15793,7 +15793,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16389,6 +16390,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17826,6 +17833,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17944,6 +17952,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index dd00ab420b8..02b7216e9d0 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -444,6 +444,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 7d3b4198f26..a013cd2c1ac 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From 872588099b49623f24fc97bd2418292d4bbe685c Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 19 Jun 2025 14:40:41 +0900
Subject: [PATCH v13] Add IGNORE NULLS/RESPECT NULLS option to Window
 functions.

Add IGNORE NULLS/RESPECT NULLS option to lead, lag, first_value,
last_value and nth_value.
---
 doc/src/sgml/func.sgml               |  38 ++-
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 403 +++++++++++++++++++++++++--
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 +
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 ++++++++++
 15 files changed, 928 insertions(+), 51 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 8d7d9a2f3e8..6b7c22a2109 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23533,7 +23533,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23558,7 +23558,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23581,7 +23581,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23595,7 +23595,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23609,7 +23609,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23658,18 +23658,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..20355effb95 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,9 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +99,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +202,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1294,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -2619,14 +2655,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2718,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3255,274 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	do
+	{
+		int			inframe;
+		int			v;
+
+		if (!window_gettupleslot(winobj, abs_pos, slot))
+			goto out_of_frame;
+
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3681,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3723,57 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
-	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3825,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 26a3e050086..9705c8ef2e8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2572,6 +2572,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 50f53159d58..547b7f7e465 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15738,7 +15738,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15771,7 +15771,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16367,6 +16368,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17793,6 +17800,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17911,6 +17919,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ba12678d1cb..8bedaf2f750 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 01510b01b64..2f0a77d2cc2 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -577,6 +577,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -600,6 +611,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From f47fee700e97f0f5f2537676671885f376619871 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 25 Jun 2025 14:55:33 +0900
Subject: [PATCH v14] Add IGNORE NULLS/RESPECT NULLS option to Window
 functions.

Add IGNORE NULLS/RESPECT NULLS option to lead, lag, first_value,
last_value and nth_value.
---
 doc/src/sgml/func.sgml               |  38 ++-
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 437 +++++++++++++++++++++++++--
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 +
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++
 15 files changed, 962 insertions(+), 51 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 224d4fe5a9f..a95fdbab031 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23543,7 +23543,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23568,7 +23568,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23591,7 +23591,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23605,7 +23605,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23619,7 +23619,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23668,18 +23668,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..ba40cde550c 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,9 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +99,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +202,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1294,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -2619,14 +2655,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2718,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3255,308 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			frameOptions;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	frameOptions = winstate->frameOptions;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+		bool		gottuple = false;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/*
+		 * row_is_in_frame requires slot if following frame options are set.
+		 */
+		if (frameOptions & FRAMEOPTION_END_CURRENT_ROW &&
+			frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+			gottuple = true;
+		}
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!gottuple)
+			{
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+			}
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!gottuple)
+				{
+					if (!window_gettupleslot(winobj, abs_pos, slot))
+						goto out_of_frame;
+				}
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3715,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3757,57 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
-	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3859,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 26a3e050086..9705c8ef2e8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2572,6 +2572,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 50f53159d58..547b7f7e465 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15738,7 +15738,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15771,7 +15771,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16367,6 +16368,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17793,6 +17800,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17911,6 +17919,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ba12678d1cb..8bedaf2f750 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From fb63e9a73c475be518c393d438b6dddb3b4ca833 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 30 Jun 2025 14:21:48 +0900
Subject: [PATCH v15] Add IGNORE NULLS/RESPECT NULLS option to Window
 functions.

Add IGNORE NULLS/RESPECT NULLS option to lead, lag, first_value,
last_value and nth_value.
---
 doc/src/sgml/func.sgml               |  38 ++-
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 447 +++++++++++++++++++++++++--
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 +
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 +++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++
 15 files changed, 972 insertions(+), 51 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 224d4fe5a9f..a95fdbab031 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23543,7 +23543,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23568,7 +23568,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23591,7 +23591,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23605,7 +23605,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23619,7 +23619,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23668,18 +23668,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..9265c2754a7 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,9 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +99,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -198,6 +202,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -1263,6 +1294,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -2619,14 +2655,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2718,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3255,308 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+	int			frameOptions;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+	frameOptions = winstate->frameOptions;
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+		bool		gottuple = false;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/*
+		 * row_is_in_frame requires slot if following frame options are set.
+		 */
+		if (frameOptions & FRAMEOPTION_END_CURRENT_ROW &&
+			frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+			gottuple = true;
+		}
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winstate, abs_pos, slot);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!gottuple)
+			{
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+			}
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!gottuple)
+				{
+					if (!window_gettupleslot(winobj, abs_pos, slot))
+						goto out_of_frame;
+				}
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3715,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3757,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
-	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3869,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 26a3e050086..9705c8ef2e8 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2572,6 +2572,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 50f53159d58..547b7f7e465 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15738,7 +15738,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15771,7 +15771,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16367,6 +16368,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17793,6 +17800,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17911,6 +17919,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ba12678d1cb..8bedaf2f750 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From 5825053d159e77fc475c0201eea27b23144fcd37 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 7 Jul 2025 14:12:15 +0900
Subject: [PATCH v16] Add IGNORE NULLS/RESPECT NULLS option to Window
 functions.

Add IGNORE NULLS/RESPECT NULLS option to lead, lag, first_value,
last_value and nth_value.
---
 doc/src/sgml/func.sgml               |  38 ++-
 doc/src/sgml/syntax.sgml             |  10 +-
 src/backend/catalog/sql_features.txt |   2 +-
 src/backend/executor/nodeWindowAgg.c | 454 ++++++++++++++++++++++++---
 src/backend/optimizer/util/clauses.c |   1 +
 src/backend/parser/gram.y            |  19 +-
 src/backend/parser/parse_func.c      |   9 +
 src/backend/utils/adt/ruleutils.c    |   7 +-
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/nodes/parsenodes.h       |   1 +
 src/include/nodes/primnodes.h        |  13 +
 src/include/parser/kwlist.h          |   2 +
 src/include/windowapi.h              |   6 +
 src/test/regress/expected/window.out | 311 ++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++
 15 files changed, 969 insertions(+), 61 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 810b2b50f0d..5f3d9e85d4b 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23543,7 +23543,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23568,7 +23568,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23591,7 +23591,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23605,7 +23605,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23619,7 +23619,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23668,18 +23668,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..8def00425f6 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,9 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	int			ignore_nulls;	/* ignore nulls */
 } WindowObjectData;
 
 /*
@@ -96,6 +99,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -182,8 +186,8 @@ static void begin_partition(WindowAggState *winstate);
 static void spool_tuples(WindowAggState *winstate, int64 pos);
 static void release_partition(WindowAggState *winstate);
 
-static int	row_is_in_frame(WindowAggState *winstate, int64 pos,
-							TupleTableSlot *slot);
+static int	row_is_in_frame(WindowObject winobj, int64 pos,
+							TupleTableSlot *slot, bool fetch_tuple);
 static void update_frameheadpos(WindowAggState *winstate);
 static void update_frametailpos(WindowAggState *winstate);
 static void update_grouptailpos(WindowAggState *winstate);
@@ -198,6 +202,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -942,7 +973,7 @@ eval_windowaggregates(WindowAggState *winstate)
 		 * Exit loop if no more rows can be in frame.  Skip aggregation if
 		 * current row is not in frame but there might be more in the frame.
 		 */
-		ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
+		ret = row_is_in_frame(agg_winobj, winstate->aggregatedupto, agg_row_slot, false);
 		if (ret < 0)
 			break;
 		if (ret == 0)
@@ -1263,6 +1294,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -1412,8 +1448,8 @@ release_partition(WindowAggState *winstate)
  * to our window framing rule
  *
  * The caller must have already determined that the row is in the partition
- * and fetched it into a slot.  This function just encapsulates the framing
- * rules.
+ * and fetched it into a slot if fetch_tuple is false.
+.* This function just encapsulates the framing rules.
  *
  * Returns:
  * -1, if the row is out of frame and no succeeding rows can be in frame
@@ -1423,8 +1459,9 @@ release_partition(WindowAggState *winstate)
  * May clobber winstate->temp_slot_2.
  */
 static int
-row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
+row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot, bool fetch_tuple)
 {
+	WindowAggState *winstate = winobj->winstate;
 	int			frameOptions = winstate->frameOptions;
 
 	Assert(pos >= 0);			/* else caller error */
@@ -1453,9 +1490,13 @@ row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
 		else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
 		{
 			/* following row that is not peer is out of frame */
-			if (pos > winstate->currentpos &&
-				!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
-				return -1;
+			if (pos > winstate->currentpos)
+			{
+				if (fetch_tuple)
+					window_gettupleslot(winobj, pos, slot);
+				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
+					return -1;
+			}
 		}
 		else
 			Assert(false);
@@ -2619,14 +2660,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2723,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3260,290 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winobj, abs_pos, slot, true);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3702,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3744,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
-	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3856,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3624,7 +4008,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		goto out_of_frame;
 
 	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
 		goto out_of_frame;
 
 	if (isout)
diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index f45131c34c5..2765d794d20 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2572,6 +2572,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 70a0d832a11..27adff5f9d6 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15796,7 +15796,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15829,7 +15829,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16425,6 +16426,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17851,6 +17858,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17969,6 +17977,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 28e2e8dc0fd..5933e64e9b3 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

662c662
< select x, lag(x, 1) over (order by x), lead(x, 3) over (order by x)
---
> select x, lag(x, 1) ignore nulls over (order by x), lead(x, 3) ignore nulls over (order by x)
681c681
< 	last_value(ten) over (partition by four order by ten)
---
> 	last_value(ten) ignore nulls over (partition by four order by ten)
709c709
< 	last_value(ten) over (partition by four order by ten range between unbounded preceding and current row)
---
> 	last_value(ten) ignore nulls over (partition by four order by ten range between unbounded preceding and current row)
737c737
< 	last_value(ten) over (partition by four order by ten range between unbounded preceding and unbounded following)
---
> 	last_value(ten) ignore nulls over (partition by four order by ten range between unbounded preceding and unbounded following)
765c765
< 	last_value(ten/4) over (partition by four order by ten/4 range between unbounded preceding and current row)
---
> 	last_value(ten/4) ignore nulls over (partition by four order by ten/4 range between unbounded preceding and current row)
793c793
< 	last_value(ten/4) over (partition by four order by ten/4 rows between unbounded preceding and current row)
---
> 	last_value(ten/4) ignore nulls over (partition by four order by ten/4 rows between unbounded preceding and current row)
938c938
< SELECT first_value(unique1) over (ORDER BY four rows between current row and 2 following exclude current row),
---
> SELECT first_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude current row),
955c955
< SELECT first_value(unique1) over (ORDER BY four rows between current row and 2 following exclude group),
---
> SELECT first_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude group),
972c972
< SELECT first_value(unique1) over (ORDER BY four rows between current row and 2 following exclude ties),
---
> SELECT first_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude ties),
989c989
< SELECT last_value(unique1) over (ORDER BY four rows between current row and 2 following exclude current row),
---
> SELECT last_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude current row),
1006c1006
< SELECT last_value(unique1) over (ORDER BY four rows between current row and 2 following exclude group),
---
> SELECT last_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude group),
1023c1023
< SELECT last_value(unique1) over (ORDER BY four rows between current row and 2 following exclude ties),
---
> SELECT last_value(unique1) ignore nulls over (ORDER BY four rows between current row and 2 following exclude ties),
1159,1161c1159,1161
< SELECT first_value(unique1) over w,
< 	nth_value(unique1, 2) over w AS nth_2,
< 	last_value(unique1) over w, unique1, four
---
> SELECT first_value(unique1) ignore nulls over w,
> 	nth_value(unique1, 2) ignore nulls over w AS nth_2,
> 	last_value(unique1) ignore nulls over w, unique1, four
1631,1633c1631,1633
< select first_value(salary) over(order by salary range between 1000 preceding and 1000 following),
< 	lead(salary) over(order by salary range between 1000 preceding and 1000 following),
< 	nth_value(salary, 1) over(order by salary range between 1000 preceding and 1000 following),
---
> select first_value(salary) ignore nulls over(order by salary range between 1000 preceding and 1000 following),
> 	lead(salary) ignore nulls over(order by salary range between 1000 preceding and 1000 following),
> 	nth_value(salary, 1) ignore nulls over(order by salary range between 1000 preceding and 1000 following),
1649,1650c1649,1650
< select last_value(salary) over(order by salary range between 1000 preceding and 1000 following),
< 	lag(salary) over(order by salary range between 1000 preceding and 1000 following),
---
> select last_value(salary) ignore nulls over(order by salary range between 1000 preceding and 1000 following),
> 	lag(salary) ignore nulls over(order by salary range between 1000 preceding and 1000 following),
1666c1666
< select first_value(salary) over(order by salary range between 1000 following and 3000 following
---
> select first_value(salary) ignore nulls over(order by salary range between 1000 following and 3000 following
1668,1669c1668,1669
< 	lead(salary) over(order by salary range between 1000 following and 3000 following exclude ties),
< 	nth_value(salary, 1) over(order by salary range between 1000 following and 3000 following
---
> 	lead(salary) ignore nulls over(order by salary range between 1000 following and 3000 following exclude ties),
> 	nth_value(salary, 1) ignore nulls over(order by salary range between 1000 following and 3000 following
1686c1686
< select last_value(salary) over(order by salary range between 1000 following and 3000 following
---
> select last_value(salary) ignore nulls over(order by salary range between 1000 following and 3000 following
1688c1688
< 	lag(salary) over(order by salary range between 1000 following and 3000 following exclude group),
---
> 	lag(salary) ignore nulls over(order by salary range between 1000 following and 3000 following exclude group),
1704c1704
< select first_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> select first_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1706c1706
< 	last_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following),
---
> 	last_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following),
1722c1722
< select first_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> select first_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1724c1724
< 	last_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> 	last_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1741c1741
< select first_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> select first_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1743c1743
< 	last_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> 	last_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1760c1760
< select first_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> select first_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1762c1762
< 	last_value(salary) over(order by enroll_date range between unbounded preceding and '1 year'::interval following
---
> 	last_value(salary) ignore nulls over(order by enroll_date range between unbounded preceding and '1 year'::interval following
1781,1782c1781,1782
<        first_value(y) over w,
<        last_value(y) over w
---
>        first_value(y) ignore nulls over w,
>        last_value(y) ignore nulls over w
1801,1802c1801,1802
<        first_value(y) over w,
<        last_value(y) over w
---
>        first_value(y) ignore nulls over w,
>        last_value(y) ignore nulls over w
1821,1822c1821,1822
<        first_value(y) over w,
<        last_value(y) over w
---
>        first_value(y) ignore nulls over w,
>        last_value(y) ignore nulls over w
1841,1842c1841,1842
<        first_value(y) over w,
<        last_value(y) over w
---
>        first_value(y) ignore nulls over w,
>        last_value(y) ignore nulls over w
2001c2001
< select x, last_value(x) over (order by x::smallint range between current row and 2147450884 following)
---
> select x, last_value(x) ignore nulls over (order by x::smallint range between current row and 2147450884 following)
2010c2010
< select x, last_value(x) over (order by x::smallint desc range between current row and 2147450885 following)
---
> select x, last_value(x) ignore nulls over (order by x::smallint desc range between current row and 2147450885 following)
2019c2019
< select x, last_value(x) over (order by x range between current row and 4 following)
---
> select x, last_value(x) ignore nulls over (order by x range between current row and 4 following)
2028c2028
< select x, last_value(x) over (order by x desc range between current row and 5 following)
---
> select x, last_value(x) ignore nulls over (order by x desc range between current row and 5 following)
2037c2037
< select x, last_value(x) over (order by x range between current row and 4 following)
---
> select x, last_value(x) ignore nulls over (order by x range between current row and 4 following)
2046c2046
< select x, last_value(x) over (order by x desc range between current row and 5 following)
---
> select x, last_value(x) ignore nulls over (order by x desc range between current row and 5 following)
2073c2073
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2091c2091
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2109c2109
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2127c2127
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2145c2145
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2163c2163
< select id, f_float4, first_value(id) over w, last_value(id) over w
---
> select id, f_float4, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2168c2168
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2186c2186
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2204c2204
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2222c2222
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2240c2240
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2258c2258
< select id, f_float8, first_value(id) over w, last_value(id) over w
---
> select id, f_float8, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2263c2263
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2281c2281
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2299c2299
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2307c2307
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2325c2325
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2343c2343
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2361c2361
< select id, f_numeric, first_value(id) over w, last_value(id) over w
---
> select id, f_numeric, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2388c2388
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2408c2408
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2428c2428
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2433c2433
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2453c2453
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2473c2473
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2493c2493
< select id, f_time, first_value(id) over w, last_value(id) over w
---
> select id, f_time, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2499c2499
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2519c2519
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2539c2539
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2544c2544
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2564c2564
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2584c2584
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2604c2604
< select id, f_timetz, first_value(id) over w, last_value(id) over w
---
> select id, f_timetz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2610c2610
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2630c2630
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2650c2650
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2655c2655
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2675c2675
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2695c2695
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2715c2715
< select id, f_interval, first_value(id) over w, last_value(id) over w
---
> select id, f_interval, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2721c2721
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2741c2741
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2761c2761
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2766c2766
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2786c2786
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2806c2806
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2826c2826
< select id, f_timestamptz, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamptz, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2832c2832
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2852c2852
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2872c2872
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2877c2877
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2897c2897
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2917c2917
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
2937c2937
< select id, f_timestamp, first_value(id) over w, last_value(id) over w
---
> select id, f_timestamp, first_value(id) ignore nulls over w, last_value(id) ignore nulls over w
3253,3255c3253,3255
< select first_value(salary) over(order by enroll_date groups between 1 preceding and 1 following),
< 	lead(salary) over(order by enroll_date groups between 1 preceding and 1 following),
< 	nth_value(salary, 1) over(order by enroll_date groups between 1 preceding and 1 following),
---
> select first_value(salary) ignore nulls over(order by enroll_date groups between 1 preceding and 1 following),
> 	lead(salary) ignore nulls over(order by enroll_date groups between 1 preceding and 1 following),
> 	nth_value(salary, 1) ignore nulls over(order by enroll_date groups between 1 preceding and 1 following),
3271,3272c3271,3272
< select last_value(salary) over(order by enroll_date groups between 1 preceding and 1 following),
< 	lag(salary) over(order by enroll_date groups between 1 preceding and 1 following),
---
> select last_value(salary) ignore nulls over(order by enroll_date groups between 1 preceding and 1 following),
> 	lag(salary) ignore nulls over(order by enroll_date groups between 1 preceding and 1 following),
3288c3288
< select first_value(salary) over(order by enroll_date groups between 1 following and 3 following
---
> select first_value(salary) ignore nulls over(order by enroll_date groups between 1 following and 3 following
3290,3291c3290,3291
< 	lead(salary) over(order by enroll_date groups between 1 following and 3 following exclude ties),
< 	nth_value(salary, 1) over(order by enroll_date groups between 1 following and 3 following
---
> 	lead(salary) ignore nulls over(order by enroll_date groups between 1 following and 3 following exclude ties),
> 	nth_value(salary, 1) ignore nulls over(order by enroll_date groups between 1 following and 3 following
3308c3308
< select last_value(salary) over(order by enroll_date groups between 1 following and 3 following
---
> select last_value(salary) ignore nulls over(order by enroll_date groups between 1 following and 3 following
3310c3310
< 	lag(salary) over(order by enroll_date groups between 1 following and 3 following exclude group),
---
> 	lag(salary) ignore nulls over(order by enroll_date groups between 1 following and 3 following exclude group),

From b88424b08f6767b3902048b009fb23fe05301fe0 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:47 +0900
Subject: [PATCH v17 1/6] Modify parse/analysis modules to accept
 RESPECT/IGNORE NULLS option.

Following changes have been made to parse//analysis modules.

- add IGNORE_P RESPECT_P keywords

- add "null_treatment" to func_expr after filter_clause and before
  over_clause as the SQL standard requries. null_treatment is resolved
  to either PARSER_IGNORE_NULLS, PARSER_RESPECT_NULLS or
  NO_NULLTREATMENT

- add "ignore_nulls" to WindowFunc and FuncCall
---
 src/backend/parser/gram.y       | 19 ++++++++++++++-----
 src/backend/parser/parse_func.c |  9 +++++++++
 src/include/nodes/parsenodes.h  |  1 +
 src/include/nodes/primnodes.h   | 13 +++++++++++++
 src/include/parser/kwlist.h     |  2 ++
 5 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 73345bb3c70..5136e0992d2 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15803,7 +15803,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15836,7 +15836,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16432,6 +16433,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17858,6 +17865,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17976,6 +17984,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 86a236bd58b..9ec6d79d834 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.25.1

From 37fddc904ea66153e2ead1d40c2337854d61109f Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:47 +0900
Subject: [PATCH v17 2/6] Modify get_windowfunc_expr_helper to handle IGNORE
 NULLS option.

---
 src/backend/utils/adt/ruleutils.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
-- 
2.25.1

From 2a1eac74e7b1fbb4e53bf617c12e940f9bfbedb7 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:47 +0900
Subject: [PATCH v17 3/6] Modify eval_const_expressions_mutator to handle
 IGNORE NULLS option.

---
 src/backend/optimizer/util/clauses.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 6f0b338d2cd..92e0f14fa54 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2576,6 +2576,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
-- 
2.25.1

From 50ee381124728a89440c08a4ce16b9014ac6e2fc Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:47 +0900
Subject: [PATCH v17 4/6] Modify executor and window functions to handle IGNORE
 NULLS.

Following changes have been made to executor and window functions
modules.

- New window function API WinCheckAndInitializeNullTreatment() is
  added. Window functions should call this to express if they accept a
  null treatment clause or not.  If they do not, an error is raised in
  this function. Built-in window functions are modified to call it.

- WinGetFuncArgInPartition is modified to handle IGNORE NULLS.

- WinGetFuncArgInFrame is modified to handle IGNORE NULLS. The actual
  workhorse for this is ignorenulls_getfuncarginframe.

- While searching not null rows, to not scan tuples over and over
  again, "notnull_info" cache module added. This holds 2-bit info for
  each tuple, to keep whether the tuple has already been checked if it
  is not yet checked, null or not null. The notnull_info is added to
  WindowObjectData.
---
 src/backend/executor/nodeWindowAgg.c | 458 +++++++++++++++++++++++++--
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/windowapi.h              |   6 +
 3 files changed, 439 insertions(+), 35 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..85883958e8e 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,13 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	/*
+	 * Null treatment options. One of: NO_NULLTREATMENT, PARSER_IGNORE_NULLS,
+	 * PARSER_RESPECT_NULLS or IGNORE_NULLS.
+	 */
+	int			ignore_nulls;
 } WindowObjectData;
 
 /*
@@ -96,6 +103,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -182,8 +190,8 @@ static void begin_partition(WindowAggState *winstate);
 static void spool_tuples(WindowAggState *winstate, int64 pos);
 static void release_partition(WindowAggState *winstate);
 
-static int	row_is_in_frame(WindowAggState *winstate, int64 pos,
-							TupleTableSlot *slot);
+static int	row_is_in_frame(WindowObject winobj, int64 pos,
+							TupleTableSlot *slot, bool fetch_tuple);
 static void update_frameheadpos(WindowAggState *winstate);
 static void update_frametailpos(WindowAggState *winstate);
 static void update_grouptailpos(WindowAggState *winstate);
@@ -198,6 +206,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -942,7 +977,7 @@ eval_windowaggregates(WindowAggState *winstate)
 		 * Exit loop if no more rows can be in frame.  Skip aggregation if
 		 * current row is not in frame but there might be more in the frame.
 		 */
-		ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
+		ret = row_is_in_frame(agg_winobj, winstate->aggregatedupto, agg_row_slot, false);
 		if (ret < 0)
 			break;
 		if (ret == 0)
@@ -1263,6 +1298,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -1412,8 +1452,8 @@ release_partition(WindowAggState *winstate)
  * to our window framing rule
  *
  * The caller must have already determined that the row is in the partition
- * and fetched it into a slot.  This function just encapsulates the framing
- * rules.
+ * and fetched it into a slot if fetch_tuple is false.
+.* This function just encapsulates the framing rules.
  *
  * Returns:
  * -1, if the row is out of frame and no succeeding rows can be in frame
@@ -1423,8 +1463,9 @@ release_partition(WindowAggState *winstate)
  * May clobber winstate->temp_slot_2.
  */
 static int
-row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
+row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot, bool fetch_tuple)
 {
+	WindowAggState *winstate = winobj->winstate;
 	int			frameOptions = winstate->frameOptions;
 
 	Assert(pos >= 0);			/* else caller error */
@@ -1453,9 +1494,13 @@ row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
 		else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
 		{
 			/* following row that is not peer is out of frame */
-			if (pos > winstate->currentpos &&
-				!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
-				return -1;
+			if (pos > winstate->currentpos)
+			{
+				if (fetch_tuple)
+					window_gettupleslot(winobj, pos, slot);
+				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
+					return -1;
+			}
 		}
 		else
 			Assert(false);
@@ -2619,14 +2664,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2727,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3264,290 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winobj, abs_pos, slot, true);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3706,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3748,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
-	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3860,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3624,7 +4012,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		goto out_of_frame;
 
 	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
 		goto out_of_frame;
 
 	if (isout)
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
-- 
2.25.1

From f90eac87f324fd4888bfca4ced7f11b525275475 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:47 +0900
Subject: [PATCH v17 5/6] Modify documents to add null treatment clause.

---
 doc/src/sgml/func.sgml               | 38 +++++++++++++++++-----------
 doc/src/sgml/syntax.sgml             | 10 +++++---
 src/backend/catalog/sql_features.txt |  2 +-
 3 files changed, 30 insertions(+), 20 deletions(-)

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index de5b5929ee0..4106e1768d8 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -23543,7 +23543,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23568,7 +23568,7 @@ SELECT count(*) FROM sometable;
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -23591,7 +23591,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23605,7 +23605,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23619,7 +23619,7 @@ SELECT count(*) FROM sometable;
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -23668,18 +23668,26 @@ SELECT count(*) FROM sometable;
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
diff --git a/doc/src/sgml/syntax.sgml b/doc/src/sgml/syntax.sgml
index 916189a7d68..237d7306fe8 100644
--- a/doc/src/sgml/syntax.sgml
+++ b/doc/src/sgml/syntax.sgml
@@ -1834,8 +1834,8 @@ FROM generate_series(1,10) AS s(i);
     The syntax of a window function call is one of the following:
 
 <synopsis>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
-<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
+<replaceable>function_name</replaceable> (<optional><replaceable>expression</replaceable> <optional>, <replaceable>expression</replaceable> ... </optional></optional>) <optional>null treatment</optional> [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER <replaceable>window_name</replaceable>
 <replaceable>function_name</replaceable> ( * ) [ FILTER ( WHERE <replaceable>filter_clause</replaceable> ) ] OVER ( <replaceable class="parameter">window_definition</replaceable> )
 </synopsis>
@@ -1873,7 +1873,9 @@ EXCLUDE NO OTHERS
 
    <para>
     Here, <replaceable>expression</replaceable> represents any value
-    expression that does not itself contain window function calls.
+    expression that does not itself contain window function calls. Some
+    non-aggregate functions allow a <literal>null treatment</literal> clause,
+    described in <xref linkend="functions-window"/>.
    </para>
 
    <para>
@@ -2048,7 +2050,7 @@ EXCLUDE NO OTHERS
 
    <para>
     The built-in window functions are described in <xref
-    linkend="functions-window-table"/>.  Other window functions can be added by
+    linkend="functions-window-table"/>. Other window functions can be added by
     the user.  Also, any built-in or user-defined general-purpose or
     statistical aggregate can be used as a window function.  (Ordered-set
     and hypothetical-set aggregates cannot presently be used as window functions.)
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index ebe85337c28..3a8ad201607 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -518,7 +518,7 @@ T612	Advanced OLAP operations			YES
 T613	Sampling			YES	
 T614	NTILE function			YES	
 T615	LEAD and LAG functions			YES	
-T616	Null treatment option for LEAD and LAG functions			NO	
+T616	Null treatment option for LEAD and LAG functions			YES	
 T617	FIRST_VALUE and LAST_VALUE functions			YES	
 T618	NTH_VALUE function			NO	function exists, but some options missing
 T619	Nested window functions			NO	
-- 
2.25.1

From 77b39553d575c8e24b99e165a5d315a717051638 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 25 Jul 2025 16:22:48 +0900
Subject: [PATCH v17 6/6] Modify window function regression tests to test null
 treatment clause.

---
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++++
 2 files changed, 458 insertions(+)

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From 4db6a5d9a69b82af870232233e4ef77ac8b4153e Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 1/6] Modify parse/analysis modules to accept
 RESPECT/IGNORE NULLS option.

Following changes have been made to parse//analysis modules.

- add IGNORE_P RESPECT_P keywords

- add "null_treatment" to func_expr after filter_clause and before
  over_clause as the SQL standard requries. null_treatment is resolved
  to either PARSER_IGNORE_NULLS, PARSER_RESPECT_NULLS or
  NO_NULLTREATMENT

- add "ignore_nulls" to WindowFunc and FuncCall
---
 src/backend/parser/gram.y       | 19 ++++++++++++++-----
 src/backend/parser/parse_func.c |  9 +++++++++
 src/include/nodes/parsenodes.h  |  1 +
 src/include/nodes/primnodes.h   | 13 +++++++++++++
 src/include/parser/kwlist.h     |  2 ++
 5 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index db43034b9db..e7847a7b7a5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15791,7 +15791,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15824,7 +15824,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16420,6 +16421,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17846,6 +17853,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17964,6 +17972,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 583bbbf232f..3772c514b1e 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -98,6 +98,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : 0);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -514,6 +515,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -834,6 +842,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 86a236bd58b..9ec6d79d834 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.25.1

From 4ca53852c6af568fd5aca25f2dc01593338fc561 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 2/6] Modify get_windowfunc_expr_helper to handle IGNORE
 NULLS option.

---
 src/backend/utils/adt/ruleutils.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 3d6e6bdbfd2..4e837d2afea 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
-- 
2.25.1

From 8a95f6fd4ab49e97cbd54d55278fe91bdcf30e54 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 3/6] Modify eval_const_expressions_mutator to handle
 IGNORE NULLS option.

---
 src/backend/optimizer/util/clauses.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index 6f0b338d2cd..92e0f14fa54 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2576,6 +2576,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
-- 
2.25.1

From 163577c9191d63b80083a153fe2604227c3f9420 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 4/6] Modify executor and window functions to handle IGNORE
 NULLS.

Following changes have been made to executor and window functions
modules.

- New window function API WinCheckAndInitializeNullTreatment() is
  added. Window functions should call this to express if they accept a
  null treatment clause or not.  If they do not, an error is raised in
  this function. Built-in window functions are modified to call it.

- WinGetFuncArgInPartition is modified to handle IGNORE NULLS.

- WinGetFuncArgInFrame is modified to handle IGNORE NULLS. The actual
  workhorse for this is ignorenulls_getfuncarginframe.

- While searching not null rows, to not scan tuples over and over
  again, "notnull_info" cache module added. This holds 2-bit info for
  each tuple, to keep whether the tuple has already been checked if it
  is not yet checked, null or not null. The notnull_info is added to
  WindowObjectData.
---
 src/backend/executor/nodeWindowAgg.c | 458 +++++++++++++++++++++++++--
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/windowapi.h              |   6 +
 3 files changed, 439 insertions(+), 35 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..85883958e8e 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,13 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+	/*
+	 * Null treatment options. One of: NO_NULLTREATMENT, PARSER_IGNORE_NULLS,
+	 * PARSER_RESPECT_NULLS or IGNORE_NULLS.
+	 */
+	int			ignore_nulls;
 } WindowObjectData;
 
 /*
@@ -96,6 +103,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	int			ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -182,8 +190,8 @@ static void begin_partition(WindowAggState *winstate);
 static void spool_tuples(WindowAggState *winstate, int64 pos);
 static void release_partition(WindowAggState *winstate);
 
-static int	row_is_in_frame(WindowAggState *winstate, int64 pos,
-							TupleTableSlot *slot);
+static int	row_is_in_frame(WindowObject winobj, int64 pos,
+							TupleTableSlot *slot, bool fetch_tuple);
 static void update_frameheadpos(WindowAggState *winstate);
 static void update_frametailpos(WindowAggState *winstate);
 static void update_grouptailpos(WindowAggState *winstate);
@@ -198,6 +206,33 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull, bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -942,7 +977,7 @@ eval_windowaggregates(WindowAggState *winstate)
 		 * Exit loop if no more rows can be in frame.  Skip aggregation if
 		 * current row is not in frame but there might be more in the frame.
 		 */
-		ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
+		ret = row_is_in_frame(agg_winobj, winstate->aggregatedupto, agg_row_slot, false);
 		if (ret < 0)
 			break;
 		if (ret == 0)
@@ -1263,6 +1298,11 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (perfuncstate->winobj->ignore_nulls == IGNORE_NULLS)
+				memset(perfuncstate->winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -1412,8 +1452,8 @@ release_partition(WindowAggState *winstate)
  * to our window framing rule
  *
  * The caller must have already determined that the row is in the partition
- * and fetched it into a slot.  This function just encapsulates the framing
- * rules.
+ * and fetched it into a slot if fetch_tuple is false.
+.* This function just encapsulates the framing rules.
  *
  * Returns:
  * -1, if the row is out of frame and no succeeding rows can be in frame
@@ -1423,8 +1463,9 @@ release_partition(WindowAggState *winstate)
  * May clobber winstate->temp_slot_2.
  */
 static int
-row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
+row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot, bool fetch_tuple)
 {
+	WindowAggState *winstate = winobj->winstate;
 	int			frameOptions = winstate->frameOptions;
 
 	Assert(pos >= 0);			/* else caller error */
@@ -1453,9 +1494,13 @@ row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
 		else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
 		{
 			/* following row that is not peer is out of frame */
-			if (pos > winstate->currentpos &&
-				!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
-				return -1;
+			if (pos > winstate->currentpos)
+			{
+				if (fetch_tuple)
+					window_gettupleslot(winobj, pos, slot);
+				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
+					return -1;
+			}
 		}
 		else
 			Assert(false);
@@ -2619,14 +2664,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2727,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3264,290 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winobj, abs_pos, slot, true);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates, argno),
+								 econtext, isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth(winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+#define	INIT_NOT_NULL_INFO_NUM	128 /* initial number of notnull info members */
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3706,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3748,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
-	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3860,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3624,7 +4012,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		goto out_of_frame;
 
 	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
 		goto out_of_frame;
 
 	if (isout)
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
-- 
2.25.1

From f38a1fd9ecbabbe6fe975e039d7b29931a2831e0 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 5/6] Modify documents to add null treatment clause.

---
 doc/src/sgml/func/func-window.sgml | 38 ++++++++++++++++++------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/doc/src/sgml/func/func-window.sgml b/doc/src/sgml/func/func-window.sgml
index cce0165b952..bcf755c9ebc 100644
--- a/doc/src/sgml/func/func-window.sgml
+++ b/doc/src/sgml/func/func-window.sgml
@@ -140,7 +140,7 @@
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -165,7 +165,7 @@
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -188,7 +188,7 @@
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -202,7 +202,7 @@
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -216,7 +216,7 @@
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -265,18 +265,26 @@
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
-- 
2.25.1

From c9b09bd64a43c4155380eabd67433a91966588fd Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 16 Aug 2025 18:29:23 +0900
Subject: [PATCH v18 6/6] Modify window function regression tests to test null
 treatment clause.

---
 src/test/regress/expected/window.out | 311 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 147 +++++++++++++
 2 files changed, 458 insertions(+)

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..f929d81bc8a 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,314 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..1f8c8669436 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,150 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.25.1

From f860f4cc377b66c1f5a407476fa616e5bcf2b855 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 1/6] Modify parse/analysis modules to accept
 RESPECT/IGNORE NULLS option.

Following changes have been made to parse//analysis modules.

- add IGNORE_P RESPECT_P keywords

- add "null_treatment" to func_expr after filter_clause and before
  over_clause as the SQL standard requries. null_treatment is resolved
  to either PARSER_IGNORE_NULLS, PARSER_RESPECT_NULLS or
  NO_NULLTREATMENT

- add "ignore_nulls" to WindowFunc and FuncCall
---
 src/backend/parser/gram.y       | 19 ++++++++++++++-----
 src/backend/parser/parse_func.c |  9 +++++++++
 src/include/nodes/parsenodes.h  |  1 +
 src/include/nodes/primnodes.h   | 13 +++++++++++++
 src/include/parser/kwlist.h     |  2 ++
 5 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9fd48acb1f8..e7ad62c5e5e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -631,7 +631,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -729,7 +729,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -764,7 +764,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15792,7 +15792,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15825,7 +15825,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16421,6 +16422,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17847,6 +17854,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17965,6 +17973,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index c43020a769d..778d69c6f3c 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -100,6 +100,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : NO_NULLTREATMENT);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -518,6 +519,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -840,6 +848,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 4ed14fc5b78..95caa375fb8 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -452,6 +452,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.43.0

From b8e9eb7fd806d31a2156a8b1197d8defa6a8b0f6 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 2/6] Modify get_windowfunc_expr_helper to handle IGNORE
 NULLS option.

---
 src/backend/utils/adt/ruleutils.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 0408a95941d..867f4aea591 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11090,7 +11090,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
-- 
2.43.0

From 43a985fbef41e8a61a70dac546df5984bca27360 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 3/6] Modify eval_const_expressions_mutator to handle
 IGNORE NULLS option.

---
 src/backend/optimizer/util/clauses.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index f49bde7595b..81d768ff2a2 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2578,6 +2578,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
-- 
2.43.0

From 66dcc0ab8d6702d348d6796de7a0c70158a466c1 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 4/6] Modify executor and window functions to handle IGNORE
 NULLS.

Following changes have been made to executor and window functions
modules.

- New window function API WinCheckAndInitializeNullTreatment() is
  added. Window functions should call this to express if they accept a
  null treatment clause or not.  If they do not, an error is raised in
  this function. Built-in window functions are modified to call it.

- WinGetFuncArgInPartition is modified to handle IGNORE NULLS.

- WinGetFuncArgInFrame is modified to handle IGNORE NULLS. The actual
  workhorse for this is ignorenulls_getfuncarginframe.

- While searching not null rows, to not scan tuples over and over
  again, "notnull_info" cache module added. This holds 2-bit info for
  each tuple, to keep whether the tuple has already been checked if it
  is not yet checked, null or not null. The notnull_info is added to
  WindowObjectData.
---
 src/backend/executor/nodeWindowAgg.c | 467 +++++++++++++++++++++++++--
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/windowapi.h              |   6 +
 3 files changed, 448 insertions(+), 35 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..b459c980803 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,14 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+
+	/*
+	 * Null treatment options. One of: NO_NULLTREATMENT, PARSER_IGNORE_NULLS,
+	 * PARSER_RESPECT_NULLS or IGNORE_NULLS.
+	 */
+	int			ignore_nulls;
 } WindowObjectData;
 
 /*
@@ -96,6 +104,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	uint8		ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -182,8 +191,8 @@ static void begin_partition(WindowAggState *winstate);
 static void spool_tuples(WindowAggState *winstate, int64 pos);
 static void release_partition(WindowAggState *winstate);
 
-static int	row_is_in_frame(WindowAggState *winstate, int64 pos,
-							TupleTableSlot *slot);
+static int	row_is_in_frame(WindowObject winobj, int64 pos,
+							TupleTableSlot *slot, bool fetch_tuple);
 static void update_frameheadpos(WindowAggState *winstate);
 static void update_frametailpos(WindowAggState *winstate);
 static void update_grouptailpos(WindowAggState *winstate);
@@ -198,6 +207,34 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull,
+									 bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -942,7 +979,8 @@ eval_windowaggregates(WindowAggState *winstate)
 		 * Exit loop if no more rows can be in frame.  Skip aggregation if
 		 * current row is not in frame but there might be more in the frame.
 		 */
-		ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
+		ret = row_is_in_frame(agg_winobj, winstate->aggregatedupto,
+							  agg_row_slot, false);
 		if (ret < 0)
 			break;
 		if (ret == 0)
@@ -1263,6 +1301,12 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (winobj->ignore_nulls == IGNORE_NULLS)
+				memset(winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(
+									   perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -1412,8 +1456,8 @@ release_partition(WindowAggState *winstate)
  * to our window framing rule
  *
  * The caller must have already determined that the row is in the partition
- * and fetched it into a slot.  This function just encapsulates the framing
- * rules.
+ * and fetched it into a slot if fetch_tuple is false.
+.* This function just encapsulates the framing rules.
  *
  * Returns:
  * -1, if the row is out of frame and no succeeding rows can be in frame
@@ -1423,8 +1467,10 @@ release_partition(WindowAggState *winstate)
  * May clobber winstate->temp_slot_2.
  */
 static int
-row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
+row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot,
+				bool fetch_tuple)
 {
+	WindowAggState *winstate = winobj->winstate;
 	int			frameOptions = winstate->frameOptions;
 
 	Assert(pos >= 0);			/* else caller error */
@@ -1453,9 +1499,13 @@ row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
 		else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
 		{
 			/* following row that is not peer is out of frame */
-			if (pos > winstate->currentpos &&
-				!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
-				return -1;
+			if (pos > winstate->currentpos)
+			{
+				if (fetch_tuple)
+					window_gettupleslot(winobj, pos, slot);
+				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
+					return -1;
+			}
 		}
 		else
 			Assert(false);
@@ -2619,14 +2669,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2732,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3269,294 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth
+						(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winobj, abs_pos, slot, true);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates,
+														argno), econtext,
+								 isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth
+									 (winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+/* initial number of notnull info members */
+#define	INIT_NOT_NULL_INFO_NUM	128
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3715,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3757,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
-	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3869,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3624,7 +4021,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		goto out_of_frame;
 
 	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
 		goto out_of_frame;
 
 	if (isout)
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
-- 
2.43.0

From e632d9e9261b4983393828b09d079a950f9b68ca Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 5/6] Modify documents to add null treatment clause.

---
 doc/src/sgml/func/func-window.sgml | 38 ++++++++++++++++++------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/doc/src/sgml/func/func-window.sgml b/doc/src/sgml/func/func-window.sgml
index cce0165b952..bcf755c9ebc 100644
--- a/doc/src/sgml/func/func-window.sgml
+++ b/doc/src/sgml/func/func-window.sgml
@@ -140,7 +140,7 @@
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -165,7 +165,7 @@
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -188,7 +188,7 @@
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -202,7 +202,7 @@
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -216,7 +216,7 @@
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -265,18 +265,26 @@
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
-- 
2.43.0

From 6818690e8fcdfdac51fe5d48aedf1db6fb21a9eb Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Wed, 24 Sep 2025 14:15:19 +0900
Subject: [PATCH v19 6/6] Modify window function regression tests to test null
 treatment clause.

---
 src/test/regress/expected/window.out | 406 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 162 +++++++++++
 2 files changed, 568 insertions(+)

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..a595fa28ce1 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,409 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT rank() OVER () FROM planets; -- succeeds
+ rank 
+------
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+(10 rows)
+
+SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function rank does not allow RESPECT/IGNORE NULLS
+SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function rank does not allow RESPECT/IGNORE NULLS
+SELECT dense_rank() OVER () FROM planets; -- succeeds
+ dense_rank 
+------------
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+(10 rows)
+
+SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function dense_rank does not allow RESPECT/IGNORE NULLS
+SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function dense_rank does not allow RESPECT/IGNORE NULLS
+SELECT percent_rank() OVER () FROM planets; -- succeeds
+ percent_rank 
+--------------
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+(10 rows)
+
+SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function percent_rank does not allow RESPECT/IGNORE NULLS
+SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function percent_rank does not allow RESPECT/IGNORE NULLS
+SELECT cume_dist() OVER () FROM planets; -- succeeds
+ cume_dist 
+-----------
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+(10 rows)
+
+SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function cume_dist does not allow RESPECT/IGNORE NULLS
+SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function cume_dist does not allow RESPECT/IGNORE NULLS
+SELECT ntile(1) OVER () FROM planets; -- succeeds
+ ntile 
+-------
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+(10 rows)
+
+SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function ntile does not allow RESPECT/IGNORE NULLS
+SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function ntile does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..85fc621c8db 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,165 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT rank() OVER () FROM planets; -- succeeds
+SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT dense_rank() OVER () FROM planets; -- succeeds
+SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT percent_rank() OVER () FROM planets; -- succeeds
+SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT cume_dist() OVER () FROM planets; -- succeeds
+SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT ntile(1) OVER () FROM planets; -- succeeds
+SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From 428d094b3fe209bd398f1356e81191cedf97951b Mon Sep 17 00:00:00 2001
From: Oliver Ford <oliver.f@argodevops.co.uk>
Date: Wed, 24 Sep 2025 12:53:42 +0100
Subject: [PATCH] Add uint8/uint16 to gen_node_support

---
 src/backend/nodes/gen_node_support.pl | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/backend/nodes/gen_node_support.pl b/src/backend/nodes/gen_node_support.pl
index 9ecddb14231..b24713f000b 100644
--- a/src/backend/nodes/gen_node_support.pl
+++ b/src/backend/nodes/gen_node_support.pl
@@ -1030,7 +1030,9 @@ _read${n}(void)
 			print $off "\tWRITE_INT_FIELD($f);\n";
 			print $rff "\tREAD_INT_FIELD($f);\n" unless $no_read;
 		}
-		elsif ($t eq 'uint32'
+		elsif ($t eq 'uint8'
+			|| $t eq 'uint16'
+			|| $t eq 'uint32'
 			|| $t eq 'bits32'
 			|| $t eq 'BlockNumber'
 			|| $t eq 'Index'
-- 
2.43.0

From cb9575f920fae82e2a0e7b40f243fb6980054244 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 1/6] Modify parse/analysis modules to accept
 RESPECT/IGNORE NULLS option.

Following changes have been made to parse//analysis modules.

- add IGNORE_P RESPECT_P keywords

- add "null_treatment" to func_expr after filter_clause and before
  over_clause as the SQL standard requries. null_treatment is resolved
  to either PARSER_IGNORE_NULLS, PARSER_RESPECT_NULLS or
  NO_NULLTREATMENT

- add "ignore_nulls" to WindowFunc and FuncCall
---
 src/backend/parser/gram.y       | 19 ++++++++++++++-----
 src/backend/parser/parse_func.c |  9 +++++++++
 src/include/nodes/parsenodes.h  |  1 +
 src/include/nodes/primnodes.h   | 13 +++++++++++++
 src/include/parser/kwlist.h     |  2 ++
 5 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index f1def67ac7c..57bf7a7c7f2 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -632,7 +632,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	window_clause window_definition_list opt_partition_clause
 %type <windef>	window_definition over_clause window_specification
 				opt_frame_clause frame_extent frame_bound
-%type <ival>	opt_window_exclusion_clause
+%type <ival>	null_treatment opt_window_exclusion_clause
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 %type <boolean> opt_unique_null_treatment
@@ -730,7 +730,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	HANDLER HAVING HEADER_P HOLD HOUR_P
 
-	IDENTITY_P IF_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
+	IDENTITY_P IF_P IGNORE_P ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P INCLUDE
 	INCLUDING INCREMENT INDENT INDEX INDEXES INHERIT INHERITS INITIALLY INLINE_P
 	INNER_P INOUT INPUT_P INSENSITIVE INSERT INSTEAD INT_P INTEGER
 	INTERSECT INTERVAL INTO INVOKER IS ISNULL ISOLATION
@@ -765,7 +765,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECURSIVE REF_P REFERENCES REFERENCING
 	REFRESH REINDEX RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
+	RESET RESPECT_P RESTART RESTRICT RETURN RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK ROLLUP
 	ROUTINE ROUTINES ROW ROWS RULE
 
 	SAVEPOINT SCALAR SCHEMA SCHEMAS SCROLL SEARCH SECOND_P SECURITY SELECT
@@ -15805,7 +15805,7 @@ func_application: func_name '(' ')'
  * (Note that many of the special SQL functions wouldn't actually make any
  * sense as functional index entries, but we ignore that consideration here.)
  */
-func_expr: func_application within_group_clause filter_clause over_clause
+func_expr: func_application within_group_clause filter_clause null_treatment over_clause
 				{
 					FuncCall   *n = (FuncCall *) $1;
 
@@ -15838,7 +15838,8 @@ func_expr: func_application within_group_clause filter_clause over_clause
 						n->agg_within_group = true;
 					}
 					n->agg_filter = $3;
-					n->over = $4;
+					n->ignore_nulls = $4;
+					n->over = $5;
 					$$ = (Node *) n;
 				}
 			| json_aggregate_func filter_clause over_clause
@@ -16434,6 +16435,12 @@ filter_clause:
 /*
  * Window Definitions
  */
+null_treatment:
+			IGNORE_P NULLS_P						{ $$ = PARSER_IGNORE_NULLS; }
+			| RESPECT_P NULLS_P						{ $$ = PARSER_RESPECT_NULLS; }
+			| /*EMPTY*/								{ $$ = NO_NULLTREATMENT; }
+		;
+
 window_clause:
 			WINDOW window_definition_list			{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NIL; }
@@ -17861,6 +17868,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE_P
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -17979,6 +17987,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT_P
 			| RESTART
 			| RESTRICT
 			| RETURN
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index c43020a769d..778d69c6f3c 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -100,6 +100,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	bool		agg_star = (fn ? fn->agg_star : false);
 	bool		agg_distinct = (fn ? fn->agg_distinct : false);
 	bool		func_variadic = (fn ? fn->func_variadic : false);
+	int			ignore_nulls = (fn ? fn->ignore_nulls : NO_NULLTREATMENT);
 	CoercionForm funcformat = (fn ? fn->funcformat : COERCE_EXPLICIT_CALL);
 	bool		could_be_projection;
 	Oid			rettype;
@@ -518,6 +519,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 						 errmsg("%s is not an ordered-set aggregate, so it cannot have WITHIN GROUP",
 								NameListToString(funcname)),
 						 parser_errposition(pstate, location)));
+
+			/* It also can't treat nulls as a window function */
+			if (ignore_nulls != NO_NULLTREATMENT)
+				ereport(ERROR,
+						(errcode(ERRCODE_WRONG_OBJECT_TYPE),
+						 errmsg("aggregate functions do not accept RESPECT/IGNORE NULLS"),
+						 parser_errposition(pstate, location)));
 		}
 	}
 	else if (fdresult == FUNCDETAIL_WINDOWFUNC)
@@ -840,6 +848,7 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 		wfunc->winstar = agg_star;
 		wfunc->winagg = (fdresult == FUNCDETAIL_AGGREGATE);
 		wfunc->aggfilter = agg_filter;
+		wfunc->ignore_nulls = ignore_nulls;
 		wfunc->runCondition = NIL;
 		wfunc->location = location;
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index ac0e02a1db7..87c1086ec99 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -453,6 +453,7 @@ typedef struct FuncCall
 	List	   *agg_order;		/* ORDER BY (list of SortBy) */
 	Node	   *agg_filter;		/* FILTER clause, if any */
 	struct WindowDef *over;		/* OVER clause, if any */
+	int			ignore_nulls;	/* ignore nulls for window function */
 	bool		agg_within_group;	/* ORDER BY appeared in WITHIN GROUP */
 	bool		agg_star;		/* argument was really '*' */
 	bool		agg_distinct;	/* arguments were labeled DISTINCT */
diff --git a/src/include/nodes/primnodes.h b/src/include/nodes/primnodes.h
index 6dfca3cb35b..e9d8bf74145 100644
--- a/src/include/nodes/primnodes.h
+++ b/src/include/nodes/primnodes.h
@@ -579,6 +579,17 @@ typedef struct GroupingFunc
  * Collation information is irrelevant for the query jumbling, as is the
  * internal state information of the node like "winstar" and "winagg".
  */
+
+/*
+ * Null Treatment options. If specified, initially set to PARSER_IGNORE_NULLS
+ * which is then converted to IGNORE_NULLS if the window function allows the
+ * null treatment clause.
+ */
+#define NO_NULLTREATMENT 0
+#define PARSER_IGNORE_NULLS 1
+#define PARSER_RESPECT_NULLS 2
+#define IGNORE_NULLS 3
+
 typedef struct WindowFunc
 {
 	Expr		xpr;
@@ -602,6 +613,8 @@ typedef struct WindowFunc
 	bool		winstar pg_node_attr(query_jumble_ignore);
 	/* is function a simple aggregate? */
 	bool		winagg pg_node_attr(query_jumble_ignore);
+	/* ignore nulls. One of the Null Treatment options */
+	int			ignore_nulls;
 	/* token location, or -1 if unknown */
 	ParseLoc	location;
 } WindowFunc;
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index a4af3f717a1..84182eaaae2 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -202,6 +202,7 @@ PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("hour", HOUR_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("identity", IDENTITY_P, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("if", IF_P, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("ignore", IGNORE_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD, BARE_LABEL)
@@ -378,6 +379,7 @@ PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replace", REPLACE, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("replica", REPLICA, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("reset", RESET, UNRESERVED_KEYWORD, BARE_LABEL)
+PG_KEYWORD("respect", RESPECT_P, UNRESERVED_KEYWORD, AS_LABEL)
 PG_KEYWORD("restart", RESTART, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("restrict", RESTRICT, UNRESERVED_KEYWORD, BARE_LABEL)
 PG_KEYWORD("return", RETURN, UNRESERVED_KEYWORD, BARE_LABEL)
-- 
2.43.0

From 5e6c7b9306211384933b6c22af816c02ca9c5504 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 2/6] Modify get_windowfunc_expr_helper to handle IGNORE
 NULLS option.

---
 src/backend/utils/adt/ruleutils.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index c6d83d67b87..21663af6979 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -11091,7 +11091,12 @@ get_windowfunc_expr_helper(WindowFunc *wfunc, deparse_context *context,
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
+
+	if (wfunc->ignore_nulls == PARSER_IGNORE_NULLS)
+		appendStringInfoString(buf, "IGNORE NULLS ");
+
+	appendStringInfoString(buf, "OVER ");
 
 	if (context->windowClause)
 	{
-- 
2.43.0

From 1ecce664b714f4a03c57990b1be6a72dd6f26103 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 3/6] Modify eval_const_expressions_mutator to handle
 IGNORE NULLS option.

---
 src/backend/optimizer/util/clauses.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c
index f49bde7595b..81d768ff2a2 100644
--- a/src/backend/optimizer/util/clauses.c
+++ b/src/backend/optimizer/util/clauses.c
@@ -2578,6 +2578,7 @@ eval_const_expressions_mutator(Node *node,
 				newexpr->winref = expr->winref;
 				newexpr->winstar = expr->winstar;
 				newexpr->winagg = expr->winagg;
+				newexpr->ignore_nulls = expr->ignore_nulls;
 				newexpr->location = expr->location;
 
 				return (Node *) newexpr;
-- 
2.43.0

From cb0805b83d612d845a083d75094cddd22464e3dc Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 4/6] Modify executor and window functions to handle IGNORE
 NULLS.

Following changes have been made to executor and window functions
modules.

- New window function API WinCheckAndInitializeNullTreatment() is
  added. Window functions should call this to express if they accept a
  null treatment clause or not.  If they do not, an error is raised in
  this function. Built-in window functions are modified to call it.

- WinGetFuncArgInPartition is modified to handle IGNORE NULLS.

- WinGetFuncArgInFrame is modified to handle IGNORE NULLS. The actual
  workhorse for this is ignorenulls_getfuncarginframe.

- While searching not null rows, to not scan tuples over and over
  again, "notnull_info" cache module added. This holds 2-bit info for
  each tuple, to keep whether the tuple has already been checked if it
  is not yet checked, null or not null. The notnull_info is added to
  WindowObjectData.
---
 src/backend/executor/nodeWindowAgg.c | 467 +++++++++++++++++++++++++--
 src/backend/utils/adt/windowfuncs.c  |  10 +
 src/include/windowapi.h              |   6 +
 3 files changed, 448 insertions(+), 35 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 9a1acce2b5d..b459c980803 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,6 +69,14 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
+	uint8	   *notnull_info;	/* not null info */
+	int			num_notnull_info;	/* track size of the notnull_info array */
+
+	/*
+	 * Null treatment options. One of: NO_NULLTREATMENT, PARSER_IGNORE_NULLS,
+	 * PARSER_RESPECT_NULLS or IGNORE_NULLS.
+	 */
+	int			ignore_nulls;
 } WindowObjectData;
 
 /*
@@ -96,6 +104,7 @@ typedef struct WindowStatePerFuncData
 
 	bool		plain_agg;		/* is it just a plain aggregate function? */
 	int			aggno;			/* if so, index of its WindowStatePerAggData */
+	uint8		ignore_nulls;	/* ignore nulls */
 
 	WindowObject winobj;		/* object used in window function API */
 }			WindowStatePerFuncData;
@@ -182,8 +191,8 @@ static void begin_partition(WindowAggState *winstate);
 static void spool_tuples(WindowAggState *winstate, int64 pos);
 static void release_partition(WindowAggState *winstate);
 
-static int	row_is_in_frame(WindowAggState *winstate, int64 pos,
-							TupleTableSlot *slot);
+static int	row_is_in_frame(WindowObject winobj, int64 pos,
+							TupleTableSlot *slot, bool fetch_tuple);
 static void update_frameheadpos(WindowAggState *winstate);
 static void update_frametailpos(WindowAggState *winstate);
 static void update_grouptailpos(WindowAggState *winstate);
@@ -198,6 +207,34 @@ static bool are_peers(WindowAggState *winstate, TupleTableSlot *slot1,
 static bool window_gettupleslot(WindowObject winobj, int64 pos,
 								TupleTableSlot *slot);
 
+static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+										   int relpos, int seektype,
+										   bool set_mark, bool *isnull,
+										   bool *isout);
+static Datum gettuple_eval_partition(WindowObject winobj, int argno,
+									 int64 abs_pos, bool *isnull,
+									 bool *isout);
+static void init_notnull_info(WindowObject winobj);
+static void grow_notnull_info(WindowObject winobj, int64 pos);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos);
+static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+
+/*
+ * Not null info bit array consists of 2-bit items
+ */
+#define	NN_UNKNOWN	0x00		/* value not calculated yet */
+#define	NN_NULL		0x01		/* NULL */
+#define	NN_NOTNULL	0x02		/* NOT NULL */
+#define	NN_MASK		0x03		/* mask for NOT NULL MAP */
+#define NN_BITS_PER_MEMBER	2	/* number of bit in not null map */
+/* number of items per variable */
+#define NN_ITEM_PER_VAR	(BITS_PER_BYTE / NN_BITS_PER_MEMBER)
+/* convert map position to byte offset */
+#define NN_POS_TO_BYTES(pos)	((pos) / NN_ITEM_PER_VAR)
+/* bytes offset to map position */
+#define NN_BYTES_TO_POS(bytes)	((bytes) * NN_ITEM_PER_VAR)
+/* caculate shift bits */
+#define	NN_SHIFT(pos)	((pos) % NN_ITEM_PER_VAR) * NN_BITS_PER_MEMBER
 
 /*
  * initialize_windowaggregate
@@ -942,7 +979,8 @@ eval_windowaggregates(WindowAggState *winstate)
 		 * Exit loop if no more rows can be in frame.  Skip aggregation if
 		 * current row is not in frame but there might be more in the frame.
 		 */
-		ret = row_is_in_frame(winstate, winstate->aggregatedupto, agg_row_slot);
+		ret = row_is_in_frame(agg_winobj, winstate->aggregatedupto,
+							  agg_row_slot, false);
 		if (ret < 0)
 			break;
 		if (ret == 0)
@@ -1263,6 +1301,12 @@ begin_partition(WindowAggState *winstate)
 
 			winobj->markpos = -1;
 			winobj->seekpos = -1;
+
+			/* reset null map */
+			if (winobj->ignore_nulls == IGNORE_NULLS)
+				memset(winobj->notnull_info, 0,
+					   NN_POS_TO_BYTES(
+									   perfuncstate->winobj->num_notnull_info));
 		}
 	}
 
@@ -1412,8 +1456,8 @@ release_partition(WindowAggState *winstate)
  * to our window framing rule
  *
  * The caller must have already determined that the row is in the partition
- * and fetched it into a slot.  This function just encapsulates the framing
- * rules.
+ * and fetched it into a slot if fetch_tuple is false.
+.* This function just encapsulates the framing rules.
  *
  * Returns:
  * -1, if the row is out of frame and no succeeding rows can be in frame
@@ -1423,8 +1467,10 @@ release_partition(WindowAggState *winstate)
  * May clobber winstate->temp_slot_2.
  */
 static int
-row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
+row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot,
+				bool fetch_tuple)
 {
+	WindowAggState *winstate = winobj->winstate;
 	int			frameOptions = winstate->frameOptions;
 
 	Assert(pos >= 0);			/* else caller error */
@@ -1453,9 +1499,13 @@ row_is_in_frame(WindowAggState *winstate, int64 pos, TupleTableSlot *slot)
 		else if (frameOptions & (FRAMEOPTION_RANGE | FRAMEOPTION_GROUPS))
 		{
 			/* following row that is not peer is out of frame */
-			if (pos > winstate->currentpos &&
-				!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
-				return -1;
+			if (pos > winstate->currentpos)
+			{
+				if (fetch_tuple)
+					window_gettupleslot(winobj, pos, slot);
+				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
+					return -1;
+			}
 		}
 		else
 			Assert(false);
@@ -2619,14 +2669,17 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			elog(ERROR, "WindowFunc with winref %u assigned to WindowAgg with winref %u",
 				 wfunc->winref, node->winref);
 
-		/* Look for a previous duplicate window function */
+		/*
+		 * Look for a previous duplicate window function, which needs the same
+		 * ignore_nulls value
+		 */
 		for (i = 0; i <= wfuncno; i++)
 		{
 			if (equal(wfunc, perfunc[i].wfunc) &&
 				!contain_volatile_functions((Node *) wfunc))
 				break;
 		}
-		if (i <= wfuncno)
+		if (i <= wfuncno && wfunc->ignore_nulls == perfunc[i].ignore_nulls)
 		{
 			/* Found a match to an existing entry, so just mark it */
 			wfuncstate->wfuncno = i;
@@ -2679,6 +2732,8 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->argstates = wfuncstate->args;
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
+			winobj->ignore_nulls = wfunc->ignore_nulls;
+			init_notnull_info(winobj);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3214,12 +3269,294 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
+/*
+ * get tupple and evaluate in a partition
+ */
+static Datum
+gettuple_eval_partition(WindowObject winobj, int argno,
+						int64 abs_pos, bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+
+	winstate = winobj->winstate;
+	slot = winstate->temp_slot_1;
+	if (!window_gettupleslot(winobj, abs_pos, slot))
+	{
+		/* out of partition */
+		if (isout)
+			*isout = true;
+		*isnull = true;
+		return (Datum) 0;
+	}
+
+	if (isout)
+		*isout = false;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	econtext->ecxt_outertuple = slot;
+	return ExecEvalExpr((ExprState *) list_nth
+						(winobj->argstates, argno),
+						econtext, isnull);
+}
+
+/*
+ * ignorenulls_getfuncarginframe
+ * For IGNORE NULLS, get the next nonnull value in the frame, moving forward
+ * or backward until we find a value or reach the frame's end.
+ */
+static Datum
+ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
+							  int relpos, int seektype, bool set_mark,
+							  bool *isnull, bool *isout)
+{
+	WindowAggState *winstate;
+	ExprContext *econtext;
+	TupleTableSlot *slot;
+	Datum		datum;
+	int64		abs_pos;
+	int64		mark_pos;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
+
+	Assert(WindowObjectIsValid(winobj));
+	winstate = winobj->winstate;
+	econtext = winstate->ss.ps.ps_ExprContext;
+	slot = winstate->temp_slot_1;
+	datum = (Datum) 0;
+	notnull_offset = 0;
+	notnull_relpos = abs(relpos);
+
+	switch (seektype)
+	{
+		case WINDOW_SEEK_CURRENT:
+			elog(ERROR, "WINDOW_SEEK_CURRENT is not supported for WinGetFuncArgInFrame");
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+		case WINDOW_SEEK_HEAD:
+			/* rejecting relpos < 0 is easy and simplifies code below */
+			if (relpos < 0)
+				goto out_of_frame;
+			update_frameheadpos(winstate);
+			abs_pos = winstate->frameheadpos;
+			mark_pos = winstate->frameheadpos;
+			forward = 1;
+			break;
+		case WINDOW_SEEK_TAIL:
+			/* rejecting relpos > 0 is easy and simplifies code below */
+			if (relpos > 0)
+				goto out_of_frame;
+			update_frametailpos(winstate);
+			abs_pos = winstate->frametailpos - 1;
+			mark_pos = 0;		/* keep compiler quiet */
+			forward = -1;
+			break;
+		default:
+			elog(ERROR, "unrecognized window seek type: %d", seektype);
+			abs_pos = mark_pos = 0; /* keep compiler quiet */
+			break;
+	}
+
+	/*
+	 * Get the next nonnull value in the frame, moving forward or backward
+	 * until we find a value or reach the frame's end.
+	 */
+	do
+	{
+		int			inframe;
+		int			v;
+
+		/*
+		 * Check apparent out of frame case.  We need to do this because we
+		 * may not call window_gettupleslot before row_is_in_frame, which
+		 * supposes abs_pos is never negative.
+		 */
+		if (abs_pos < 0)
+			goto out_of_frame;
+
+		/* check whether row is in frame */
+		inframe = row_is_in_frame(winobj, abs_pos, slot, true);
+		if (inframe == -1)
+			goto out_of_frame;
+		else if (inframe == 0)
+			goto advance;
+
+		if (isout)
+			*isout = false;
+
+		v = get_notnull_info(winobj, abs_pos);
+		if (v == NN_NULL)		/* this row is known to be NULL */
+			goto advance;
+
+		else if (v == NN_UNKNOWN)	/* need to check NULL or not */
+		{
+			if (!window_gettupleslot(winobj, abs_pos, slot))
+				goto out_of_frame;
+
+			econtext->ecxt_outertuple = slot;
+			datum = ExecEvalExpr(
+								 (ExprState *) list_nth(winobj->argstates,
+														argno), econtext,
+								 isnull);
+			if (!*isnull)
+				notnull_offset++;
+
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
+		}
+		else					/* this row is known to be NOT NULL */
+		{
+			notnull_offset++;
+			if (notnull_offset > notnull_relpos)
+			{
+				/* to prepare exiting this loop, datum needs to be set */
+				if (!window_gettupleslot(winobj, abs_pos, slot))
+					goto out_of_frame;
+
+				econtext->ecxt_outertuple = slot;
+				datum = ExecEvalExpr(
+									 (ExprState *) list_nth
+									 (winobj->argstates, argno),
+									 econtext, isnull);
+			}
+		}
+advance:
+		abs_pos += forward;
+	} while (notnull_offset <= notnull_relpos);
+
+	if (set_mark)
+		WinSetMarkPosition(winobj, mark_pos);
+
+	return datum;
+
+out_of_frame:
+	if (isout)
+		*isout = true;
+	*isnull = true;
+	return (Datum) 0;
+}
+
+
+/*
+ * init_notnull_info
+ * Initialize non null map.
+ */
+static void
+init_notnull_info(WindowObject winobj)
+{
+/* initial number of notnull info members */
+#define	INIT_NOT_NULL_INFO_NUM	128
+
+	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+	{
+		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+
+		winobj->notnull_info = palloc0(size);
+		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+	}
+}
+
+/*
+ * grow_notnull_info
+ * expand notnull_info if necessary.
+ * pos: not null info position
+*/
+static void
+grow_notnull_info(WindowObject winobj, int64 pos)
+{
+	if (pos >= winobj->num_notnull_info)
+	{
+		for (;;)
+		{
+			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
+			Size		newsize = oldsize * 2;
+
+			winobj->notnull_info =
+				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info > pos)
+				break;
+		}
+	}
+}
+
+/*
+ * get_notnull_info
+ * retrieve a map
+ * pos: map position
+ */
+static uint8
+get_notnull_info(WindowObject winobj, int64 pos)
+{
+	uint8		mb;
+	int64		bpos;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
+}
+
+/*
+ * put_notnull_info
+ * update map
+ * pos: map position
+ */
+static void
+put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+{
+	uint8		mb;
+	int64		bpos;
+	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
+	int			shift;
+
+	grow_notnull_info(winobj, pos);
+	bpos = NN_POS_TO_BYTES(pos);
+	mb = winobj->notnull_info[bpos];
+	shift = NN_SHIFT(pos);
+	mb &= ~(NN_MASK << shift);	/* clear map */
+	mb |= (val << shift);		/* update map */
+	winobj->notnull_info[bpos] = mb;
+}
 
 /***********************************************************************
  * API exposed to window functions
  ***********************************************************************/
 
 
+/*
+ * WinCheckAndInitializeNullTreatment
+ *		Check null treatment clause and sets ignore_nulls
+ *
+ * Window functions should call this to check if they are being called with
+ * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ */
+void
+WinCheckAndInitializeNullTreatment(WindowObject winobj,
+								   bool allowNullTreatment,
+								   FunctionCallInfo fcinfo)
+{
+	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
+	{
+		HeapTuple	proctup;
+		Form_pg_proc procform;
+		Oid			funcid;
+
+		funcid = fcinfo->flinfo->fn_oid;
+		proctup = SearchSysCache1(PROCOID,
+								  ObjectIdGetDatum(funcid));
+		if (!HeapTupleIsValid(proctup))
+			elog(ERROR, "cache lookup failed for function %u", funcid);
+		procform = (Form_pg_proc) GETSTRUCT(proctup);
+		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
+			 NameStr(procform->proname));
+	}
+	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+		winobj->ignore_nulls = IGNORE_NULLS;
+
+}
+
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -3378,23 +3715,37 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 						 bool *isnull, bool *isout)
 {
 	WindowAggState *winstate;
-	ExprContext *econtext;
-	TupleTableSlot *slot;
-	bool		gottuple;
 	int64		abs_pos;
+	Datum		datum;
+	bool		null_treatment = false;
+	int			notnull_offset;
+	int			notnull_relpos;
+	int			forward;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
-	econtext = winstate->ss.ps.ps_ExprContext;
-	slot = winstate->temp_slot_1;
+
+	if (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0)
+	{
+		null_treatment = true;
+		notnull_offset = 0;
+		notnull_relpos = abs(relpos);
+		forward = relpos > 0 ? 1 : -1;
+	}
 
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
-			abs_pos = winstate->currentpos + relpos;
+			if (null_treatment)
+				abs_pos = winstate->currentpos;
+			else
+				abs_pos = winstate->currentpos + relpos;
 			break;
 		case WINDOW_SEEK_HEAD:
-			abs_pos = relpos;
+			if (null_treatment)
+				abs_pos = 0;
+			else
+				abs_pos = relpos;
 			break;
 		case WINDOW_SEEK_TAIL:
 			spool_tuples(winstate, -1);
@@ -3406,25 +3757,67 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 	}
 
-	gottuple = window_gettupleslot(winobj, abs_pos, slot);
-
-	if (!gottuple)
-	{
-		if (isout)
-			*isout = true;
-		*isnull = true;
-		return (Datum) 0;
-	}
-	else
+	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
-		if (isout)
-			*isout = false;
-		if (set_mark)
+		datum = gettuple_eval_partition(winobj, argno,
+										abs_pos, isnull, isout);
+		if (!*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
-		econtext->ecxt_outertuple = slot;
-		return ExecEvalExpr((ExprState *) list_nth(winobj->argstates, argno),
-							econtext, isnull);
+		return datum;
 	}
+
+	/*
+	 * Get the next nonnull value in the partition, moving forward or backward
+	 * until we find a value or reach the partition's end.
+	 */
+	do
+	{
+		abs_pos += forward;
+		if (abs_pos < 0)
+		{
+			/* out of partition */
+			if (isout)
+				*isout = true;
+			*isnull = true;
+			datum = 0;
+			break;
+		}
+
+		switch (get_notnull_info(winobj, abs_pos))
+		{
+			case NN_NOTNULL:	/* this row is known to be NOT NULL */
+				notnull_offset++;
+				if (notnull_offset >= notnull_relpos)
+				{
+					/* prepare to exit this loop */
+					datum = gettuple_eval_partition(winobj, argno,
+													abs_pos, isnull, isout);
+				}
+				break;
+			case NN_NULL:		/* this row is known to be NULL */
+				if (isout)
+					*isout = false;
+				*isnull = true;
+				datum = 0;
+				break;
+			default:			/* need to check NULL or not */
+				datum = gettuple_eval_partition(winobj, argno,
+												abs_pos, isnull, isout);
+				if (*isout)		/* out of partition? */
+					return datum;
+
+				if (!*isnull)
+					notnull_offset++;
+				/* record the row status */
+				put_notnull_info(winobj, abs_pos, *isnull);
+				break;
+		}
+	} while (notnull_offset < notnull_relpos);
+
+	if (!*isout && set_mark)
+		WinSetMarkPosition(winobj, abs_pos);
+
+	return datum;
 }
 
 /*
@@ -3476,6 +3869,10 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
+	if (winobj->ignore_nulls == IGNORE_NULLS)
+		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
+											 set_mark, isnull, isout);
+
 	switch (seektype)
 	{
 		case WINDOW_SEEK_CURRENT:
@@ -3624,7 +4021,7 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 		goto out_of_frame;
 
 	/* The code above does not detect all out-of-frame cases, so check */
-	if (row_is_in_frame(winstate, abs_pos, slot) <= 0)
+	if (row_is_in_frame(winobj, abs_pos, slot, false) <= 0)
 		goto out_of_frame;
 
 	if (isout)
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index bb35f3bc4a9..969f02aa59b 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -86,6 +86,7 @@ window_row_number(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	int64		curpos = WinGetCurrentPosition(winobj);
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	WinSetMarkPosition(winobj, curpos);
 	PG_RETURN_INT64(curpos + 1);
 }
@@ -141,6 +142,7 @@ window_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -203,6 +205,7 @@ window_dense_rank(PG_FUNCTION_ARGS)
 	rank_context *context;
 	bool		up;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	up = rank_up(winobj);
 	context = (rank_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(rank_context));
@@ -266,6 +269,7 @@ window_percent_rank(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -335,6 +339,7 @@ window_cume_dist(PG_FUNCTION_ARGS)
 	int64		totalrows = WinGetPartitionRowCount(winobj);
 
 	Assert(totalrows > 0);
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 
 	up = rank_up(winobj);
 	context = (rank_context *)
@@ -413,6 +418,7 @@ window_ntile(PG_FUNCTION_ARGS)
 	WindowObject winobj = PG_WINDOW_OBJECT();
 	ntile_context *context;
 
+	WinCheckAndInitializeNullTreatment(winobj, false, fcinfo);
 	context = (ntile_context *)
 		WinGetPartitionLocalMemory(winobj, sizeof(ntile_context));
 
@@ -535,6 +541,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -652,6 +659,7 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -673,6 +681,7 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -696,6 +705,7 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
+	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
diff --git a/src/include/windowapi.h b/src/include/windowapi.h
index cb2ece166b6..20cfd9e9dd9 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -28,6 +28,8 @@
 #ifndef WINDOWAPI_H
 #define WINDOWAPI_H
 
+#include "fmgr.h"
+
 /* values of "seektype" */
 #define WINDOW_SEEK_CURRENT 0
 #define WINDOW_SEEK_HEAD 1
@@ -41,6 +43,10 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern void WinCheckAndInitializeNullTreatment(WindowObject winobj,
+											   bool allowNullTreatment,
+											   FunctionCallInfo fcinfo);
+
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
-- 
2.43.0

From 112f9cd77e5fdcd78692d12b101dd5b46ea05d84 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 5/6] Modify documents to add null treatment clause.

---
 doc/src/sgml/func/func-window.sgml | 38 ++++++++++++++++++------------
 1 file changed, 23 insertions(+), 15 deletions(-)

diff --git a/doc/src/sgml/func/func-window.sgml b/doc/src/sgml/func/func-window.sgml
index cce0165b952..bcf755c9ebc 100644
--- a/doc/src/sgml/func/func-window.sgml
+++ b/doc/src/sgml/func/func-window.sgml
@@ -140,7 +140,7 @@
         </indexterm>
         <function>lag</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -165,7 +165,7 @@
         </indexterm>
         <function>lead</function> ( <parameter>value</parameter> <type>anycompatible</type>
           <optional>, <parameter>offset</parameter> <type>integer</type>
-          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> )
+          <optional>, <parameter>default</parameter> <type>anycompatible</type> </optional></optional> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anycompatible</returnvalue>
        </para>
        <para>
@@ -188,7 +188,7 @@
         <indexterm>
          <primary>first_value</primary>
         </indexterm>
-        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>first_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -202,7 +202,7 @@
         <indexterm>
          <primary>last_value</primary>
         </indexterm>
-        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> )
+        <function>last_value</function> ( <parameter>value</parameter> <type>anyelement</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -216,7 +216,7 @@
         <indexterm>
          <primary>nth_value</primary>
         </indexterm>
-        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> )
+        <function>nth_value</function> ( <parameter>value</parameter> <type>anyelement</type>, <parameter>n</parameter> <type>integer</type> ) <optional> <parameter>null treatment</parameter> </optional>
         <returnvalue>anyelement</returnvalue>
        </para>
        <para>
@@ -265,18 +265,26 @@
    Other frame specifications can be used to obtain other effects.
   </para>
 
+  <para>
+   The <literal>null treatment</literal> option must be one of:
+<synopsis>
+  RESPECT NULLS
+  IGNORE NULLS
+</synopsis>
+   If unspecified, the default is <literal>RESPECT NULLS</literal> which includes NULL
+   values in any result calculation. <literal>IGNORE NULLS</literal> ignores NULL values.
+   This option is only allowed for the following functions: <function>lag</function>,
+   <function>lead</function>, <function>first_value</function>, <function>last_value</function>,
+   <function>nth_value</function>.
+  </para>
+
   <note>
    <para>
-    The SQL standard defines a <literal>RESPECT NULLS</literal> or
-    <literal>IGNORE NULLS</literal> option for <function>lead</function>, <function>lag</function>,
-    <function>first_value</function>, <function>last_value</function>, and
-    <function>nth_value</function>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</literal>.
-    Likewise, the standard's <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
-    option for <function>nth_value</function> is not implemented: only the
-    default <literal>FROM FIRST</literal> behavior is supported.  (You can achieve
-    the result of <literal>FROM LAST</literal> by reversing the <literal>ORDER BY</literal>
+    The SQL standard defines a <literal>FROM FIRST</literal> or <literal>FROM LAST</literal>
+    option for <function>nth_value</function>. This is not implemented in
+    <productname>PostgreSQL</productname>: only the default <literal>FROM FIRST</literal>
+    behavior is supported. (You can achieve the result of <literal>FROM LAST</literal> by
+    reversing the <literal>ORDER BY</literal>
     ordering.)
    </para>
   </note>
-- 
2.43.0

From 041e95f6b11f4c9cfcd88480621aa70b8d1d753e Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 2 Oct 2025 21:06:40 +0900
Subject: [PATCH v20 6/6] Modify window function regression tests to test null
 treatment clause.

---
 src/test/regress/expected/window.out | 406 +++++++++++++++++++++++++++
 src/test/regress/sql/window.sql      | 162 +++++++++++
 2 files changed, 568 insertions(+)

diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index b86b668f433..a595fa28ce1 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5453,3 +5453,409 @@ SELECT * FROM pg_temp.f(2);
  {5}
 (5 rows)
 
+-- IGNORE NULLS tests
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+NOTICE:  view "planets_view" will be a temporary view
+SELECT pg_get_viewdef('planets_view');
+                  pg_get_viewdef                  
+--------------------------------------------------
+  SELECT name,                                   +
+     orbit,                                      +
+     lag(orbit) OVER w AS lag,                   +
+     lag(orbit) OVER w AS lag_respect,           +
+     lag(orbit) IGNORE NULLS OVER w AS lag_ignore+
+    FROM planets                                 +
+   WINDOW w AS (ORDER BY name);
+(1 row)
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit |  lag  | lag_respect | lag_ignore 
+---------+-------+-------+-------------+------------
+ earth   |       |       |             |           
+ jupiter |  4332 |       |             |           
+ mars    |       |  4332 |        4332 |       4332
+ mercury |    88 |       |             |       4332
+ neptune | 60182 |    88 |          88 |         88
+ pluto   | 90560 | 60182 |       60182 |      60182
+ saturn  | 24491 | 90560 |       90560 |      90560
+ uranus  |       | 24491 |       24491 |      24491
+ venus   |   224 |       |             |      24491
+ xyzzy   |       |   224 |         224 |        224
+(10 rows)
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+  name   | orbit | lead  | lead_respect | lead_ignore 
+---------+-------+-------+--------------+-------------
+ earth   |       |  4332 |         4332 |        4332
+ jupiter |  4332 |       |              |          88
+ mars    |       |    88 |           88 |          88
+ mercury |    88 | 60182 |        60182 |       60182
+ neptune | 60182 | 90560 |        90560 |       90560
+ pluto   | 90560 | 24491 |        24491 |       24491
+ saturn  | 24491 |       |              |         224
+ uranus  |       |   224 |          224 |         224
+ venus   |   224 |       |              |            
+ xyzzy   |       |       |              |            
+(10 rows)
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | first_value | first_value | first_value 
+---------+-------+-------------+-------------+-------------+-------------
+ earth   |       |             |        4332 |             |        4332
+ jupiter |  4332 |             |        4332 |             |        4332
+ mars    |       |             |        4332 |             |        4332
+ mercury |    88 |             |        4332 |        4332 |        4332
+ neptune | 60182 |             |        4332 |             |          88
+ pluto   | 90560 |             |        4332 |          88 |          88
+ saturn  | 24491 |             |        4332 |       60182 |       60182
+ uranus  |       |             |        4332 |       90560 |       90560
+ venus   |   224 |             |        4332 |       24491 |       24491
+ xyzzy   |       |             |        4332 |             |         224
+(10 rows)
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | nth_value | nth_value | nth_value | nth_value 
+---------+-------+-----------+-----------+-----------+-----------
+ earth   |       |      4332 |        88 |      4332 |          
+ jupiter |  4332 |      4332 |        88 |      4332 |        88
+ mars    |       |      4332 |        88 |      4332 |        88
+ mercury |    88 |      4332 |        88 |           |        88
+ neptune | 60182 |      4332 |        88 |        88 |     60182
+ pluto   | 90560 |      4332 |        88 |     60182 |     60182
+ saturn  | 24491 |      4332 |        88 |     90560 |     90560
+ uranus  |       |      4332 |        88 |     24491 |     24491
+ venus   |   224 |      4332 |        88 |           |       224
+ xyzzy   |       |      4332 |        88 |       224 |          
+(10 rows)
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | last_value | last_value | last_value | last_value 
+---------+-------+------------+------------+------------+------------
+ earth   |       |            |        224 |            |       4332
+ jupiter |  4332 |            |        224 |         88 |         88
+ mars    |       |            |        224 |      60182 |      60182
+ mercury |    88 |            |        224 |      90560 |      90560
+ neptune | 60182 |            |        224 |      24491 |      24491
+ pluto   | 90560 |            |        224 |            |      24491
+ saturn  | 24491 |            |        224 |        224 |        224
+ uranus  |       |            |        224 |            |        224
+ venus   |   224 |            |        224 |            |        224
+ xyzzy   |       |            |        224 |            |        224
+(10 rows)
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |        4332 |       4332 |           |        4332 |           
+ jupiter |  4332 |          88 |         88 |           |          88 |           
+ mars    |       |        4332 |      60182 |        88 |          88 |       4332
+ mercury |    88 |        4332 |      90560 |     60182 |       60182 |       4332
+ neptune | 60182 |          88 |      24491 |     90560 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |      24491 |           |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+  sum   
+--------
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+ 179877
+(10 rows)
+
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) RESPECT NULLS OVER () FROM planets;
+               ^
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  aggregate functions do not accept RESPECT/IGNORE NULLS
+LINE 1: SELECT sum(orbit) IGNORE NULLS OVER () FROM planets;
+               ^
+SELECT row_number() OVER () FROM planets; -- succeeds
+ row_number 
+------------
+          1
+          2
+          3
+          4
+          5
+          6
+          7
+          8
+          9
+         10
+(10 rows)
+
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function row_number does not allow RESPECT/IGNORE NULLS
+SELECT rank() OVER () FROM planets; -- succeeds
+ rank 
+------
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+    1
+(10 rows)
+
+SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function rank does not allow RESPECT/IGNORE NULLS
+SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function rank does not allow RESPECT/IGNORE NULLS
+SELECT dense_rank() OVER () FROM planets; -- succeeds
+ dense_rank 
+------------
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+          1
+(10 rows)
+
+SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function dense_rank does not allow RESPECT/IGNORE NULLS
+SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function dense_rank does not allow RESPECT/IGNORE NULLS
+SELECT percent_rank() OVER () FROM planets; -- succeeds
+ percent_rank 
+--------------
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+            0
+(10 rows)
+
+SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function percent_rank does not allow RESPECT/IGNORE NULLS
+SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function percent_rank does not allow RESPECT/IGNORE NULLS
+SELECT cume_dist() OVER () FROM planets; -- succeeds
+ cume_dist 
+-----------
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+         1
+(10 rows)
+
+SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function cume_dist does not allow RESPECT/IGNORE NULLS
+SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function cume_dist does not allow RESPECT/IGNORE NULLS
+SELECT ntile(1) OVER () FROM planets; -- succeeds
+ ntile 
+-------
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+     1
+(10 rows)
+
+SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
+ERROR:  function ntile does not allow RESPECT/IGNORE NULLS
+SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
+ERROR:  function ntile does not allow RESPECT/IGNORE NULLS
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+-------+-------------+------------+-----------+-------------+------------
+ earth   |       |             |            |           |          88 |           
+ jupiter |       |          88 |         88 |           |          88 |           
+ mars    |       |          88 |      60182 |     60182 |          88 |           
+ mercury |    88 |          88 |      90560 |     60182 |       60182 |           
+ neptune | 60182 |          88 |      24491 |     60182 |       90560 |         88
+ pluto   | 90560 |          88 |      24491 |     60182 |       24491 |      60182
+ saturn  | 24491 |       60182 |        224 |     90560 |         224 |      90560
+ uranus  |       |       90560 |        224 |     24491 |         224 |      24491
+ venus   |   224 |       24491 |        224 |       224 |             |      24491
+ xyzzy   |       |         224 |        224 |           |             |        224
+(10 rows)
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+  name   | distance | orbit | first_value | last_value | nth_value | lead_ignore | lag_ignore 
+---------+----------+-------+-------------+------------+-----------+-------------+------------
+ earth   | close    |       |             |            |           |          88 |           
+ jupiter | close    |       |          88 |         88 |           |          88 |           
+ mars    | close    |       |          88 |        224 |       224 |          88 |           
+ mercury | close    |    88 |          88 |        224 |       224 |         224 |           
+ venus   | close    |   224 |          88 |        224 |       224 |             |         88
+ neptune | far      | 60182 |       60182 |      24491 |     90560 |       90560 |           
+ pluto   | far      | 90560 |       60182 |      24491 |     90560 |       24491 |      60182
+ saturn  | far      | 24491 |       60182 |      24491 |     90560 |             |      90560
+ uranus  | far      |       |       90560 |      24491 |     24491 |             |      24491
+ xyzzy   | far      |       |       24491 |      24491 |           |             |      24491
+(10 rows)
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+ x | nth_value 
+---+-----------
+ 1 |         3
+ 2 |         3
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+ x | nth_value 
+---+-----------
+ 1 |         2
+ 2 |         2
+ 3 |         2
+ 4 |         3
+ 5 |         4
+(5 rows)
+
+--cleanup
+DROP TABLE planets CASCADE;
+NOTICE:  drop cascades to view planets_view
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 02f105f070e..85fc621c8db 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -1958,3 +1958,165 @@ $$ LANGUAGE SQL STABLE;
 
 EXPLAIN (costs off) SELECT * FROM pg_temp.f(2);
 SELECT * FROM pg_temp.f(2);
+
+-- IGNORE NULLS tests
+
+CREATE TEMPORARY TABLE planets (
+    name text,
+    distance text,
+    orbit integer
+);
+
+INSERT INTO planets VALUES
+  ('mercury', 'close', 88),
+  ('venus', 'close', 224),
+  ('earth', 'close', NULL),
+  ('mars', 'close', NULL),
+  ('jupiter', 'close', 4332),
+  ('saturn', 'far', 24491),
+  ('uranus', 'far', NULL),
+  ('neptune', 'far', 60182),
+  ('pluto', 'far', 90560),
+  ('xyzzy', 'far', NULL);
+
+-- test ruleutils
+CREATE VIEW planets_view AS
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+SELECT pg_get_viewdef('planets_view');
+
+-- lag
+SELECT name,
+       orbit,
+       lag(orbit) OVER w AS lag,
+       lag(orbit) RESPECT NULLS OVER w AS lag_respect,
+       lag(orbit) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- lead
+SELECT name,
+       orbit,
+       lead(orbit) OVER w AS lead,
+       lead(orbit) RESPECT NULLS OVER w AS lead_respect,
+       lead(orbit) IGNORE NULLS OVER w AS lead_ignore
+FROM planets
+WINDOW w AS (ORDER BY name)
+;
+
+-- first_value
+SELECT name,
+       orbit,
+       first_value(orbit) RESPECT NULLS OVER w1,
+       first_value(orbit) IGNORE NULLS OVER w1,
+       first_value(orbit) RESPECT NULLS OVER w2,
+       first_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value
+SELECT name,
+       orbit,
+       nth_value(orbit, 2) RESPECT NULLS OVER w1,
+       nth_value(orbit, 2) IGNORE NULLS OVER w1,
+       nth_value(orbit, 2) RESPECT NULLS OVER w2,
+       nth_value(orbit, 2) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- last_value
+SELECT name,
+       orbit,
+       last_value(orbit) RESPECT NULLS OVER w1,
+       last_value(orbit) IGNORE NULLS OVER w1,
+       last_value(orbit) RESPECT NULLS OVER w2,
+       last_value(orbit) IGNORE NULLS OVER w2
+FROM planets
+WINDOW w1 AS (ORDER BY name ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING),
+       w2 AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- exclude current row
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW)
+;
+
+-- valid and invalid functions
+SELECT sum(orbit) OVER () FROM planets; -- succeeds
+SELECT sum(orbit) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT sum(orbit) IGNORE NULLS OVER () FROM planets; -- fails
+SELECT row_number() OVER () FROM planets; -- succeeds
+SELECT row_number() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT row_number() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT rank() OVER () FROM planets; -- succeeds
+SELECT rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT dense_rank() OVER () FROM planets; -- succeeds
+SELECT dense_rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT dense_rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT percent_rank() OVER () FROM planets; -- succeeds
+SELECT percent_rank() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT percent_rank() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT cume_dist() OVER () FROM planets; -- succeeds
+SELECT cume_dist() RESPECT NULLS OVER () FROM planets; -- fails
+SELECT cume_dist() IGNORE NULLS OVER () FROM planets; -- fails
+SELECT ntile(1) OVER () FROM planets; -- succeeds
+SELECT ntile(1) RESPECT NULLS OVER () FROM planets; -- fails
+SELECT ntile(1) IGNORE NULLS OVER () FROM planets; -- fails
+
+-- test two consecutive nulls
+update planets set orbit=null where name='jupiter';
+SELECT name,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- test partitions
+SELECT name,
+       distance,
+       orbit,
+       first_value(orbit) IGNORE NULLS OVER w,
+       last_value(orbit) IGNORE NULLS OVER w,
+       nth_value(orbit, 2) IGNORE NULLS OVER w,
+       lead(orbit, 1) IGNORE NULLS OVER w AS lead_ignore,
+       lag(orbit, 1) IGNORE NULLS OVER w AS lag_ignore
+FROM planets
+WINDOW w AS (PARTITION BY distance ORDER BY name ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING)
+;
+
+-- nth_value without nulls
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING EXCLUDE CURRENT ROW);
+SELECT x,
+       nth_value(x,2) IGNORE NULLS OVER w
+FROM generate_series(1,5) g(x)
+WINDOW w AS (ORDER BY x ROWS BETWEEN 2 PRECEDING AND 2 FOLLOWING);
+
+--cleanup
+DROP TABLE planets CASCADE;
-- 
2.43.0

From 28f5332b50a7cf11f16d35b2860628e58077c239 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 6 Oct 2025 08:45:03 +0900
Subject: [PATCH v1] Fix Coverity issues reported in commit 25a30bbd423.

This commit fixes several issues pointed out by Coverity.

- In row_is_in_frame(), return value of window_gettupleslot() was not checked.

- WinGetFuncArgInPartition() tried to derefference "isout" pointer
 even if it's NULL in some places.

Discussion: https://postgr.es/m/202510051612.gw67jlc2iqpw%40alvherre.pgsql
---
 src/backend/executor/nodeWindowAgg.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index cf667c81211..7ccf1160dca 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1501,8 +1501,9 @@ row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot,
 			/* following row that is not peer is out of frame */
 			if (pos > winstate->currentpos)
 			{
-				if (fetch_tuple)
-					window_gettupleslot(winobj, pos, slot);
+				if (fetch_tuple)	/* need to fetch tuple? */
+					if (!window_gettupleslot(winobj, pos, slot))
+						return -1;
 				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
 					return -1;
 			}
@@ -3761,7 +3762,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	{
 		datum = gettuple_eval_partition(winobj, argno,
 										abs_pos, isnull, isout);
-		if (!*isout && set_mark)
+		if (isout && !*isout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
 		return datum;
 	}
@@ -3803,7 +3804,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			default:			/* need to check NULL or not */
 				datum = gettuple_eval_partition(winobj, argno,
 												abs_pos, isnull, isout);
-				if (*isout)		/* out of partition? */
+				if (isout && *isout)	/* out of partition? */
 					return datum;
 
 				if (!*isnull)
@@ -3814,7 +3815,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 		}
 	} while (notnull_offset < notnull_relpos);
 
-	if (!*isout && set_mark)
+	if (isout && !*isout && set_mark)
 		WinSetMarkPosition(winobj, abs_pos);
 
 	return datum;
-- 
2.43.0

From daf0113128eab7a55baf53fc676f863fba3914e8 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Tue, 7 Oct 2025 11:22:51 +0900
Subject: [PATCH v2] Fix Coverity issues reported in commit 25a30bbd423.

This commit fixes several issues pointed out by Coverity.

- In row_is_in_frame(), return value of window_gettupleslot() was not
  checked.

- WinGetFuncArgInPartition() tried to derefference "isout" pointer
  even if it's NULL in some places.

Moreover, in WinGetFuncArgInPartition refactor the do...while loop so
that the codes inside the loop simpler. Also simplify the case when
abs_pos < 0.

Discussion: https://postgr.es/m/202510051612.gw67jlc2iqpw%40alvherre.pgsql
---
 src/backend/executor/nodeWindowAgg.c | 77 ++++++++++++++--------------
 1 file changed, 38 insertions(+), 39 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index cf667c81211..0698aae37a7 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1501,8 +1501,9 @@ row_is_in_frame(WindowObject winobj, int64 pos, TupleTableSlot *slot,
 			/* following row that is not peer is out of frame */
 			if (pos > winstate->currentpos)
 			{
-				if (fetch_tuple)
-					window_gettupleslot(winobj, pos, slot);
+				if (fetch_tuple)	/* need to fetch tuple? */
+					if (!window_gettupleslot(winobj, pos, slot))
+						return -1;
 				if (!are_peers(winstate, slot, winstate->ss.ss_ScanTupleSlot))
 					return -1;
 			}
@@ -3721,6 +3722,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	int			notnull_offset;
 	int			notnull_relpos;
 	int			forward;
+	bool		myisout;
 
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
@@ -3759,63 +3761,60 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 
 	if (!null_treatment)		/* IGNORE NULLS is not specified */
 	{
+		/* get tupple and evaluate in a partition */
 		datum = gettuple_eval_partition(winobj, argno,
-										abs_pos, isnull, isout);
-		if (!*isout && set_mark)
+										abs_pos, isnull, &myisout);
+		if (!myisout && set_mark)
 			WinSetMarkPosition(winobj, abs_pos);
+		if (isout)
+			*isout = myisout;
 		return datum;
 	}
 
+	myisout = false;
+	datum = 0;
+
 	/*
 	 * Get the next nonnull value in the partition, moving forward or backward
 	 * until we find a value or reach the partition's end.
 	 */
 	do
 	{
+		int			nn_info;	/* NOT NULL info */
+
 		abs_pos += forward;
-		if (abs_pos < 0)
-		{
-			/* out of partition */
-			if (isout)
-				*isout = true;
-			*isnull = true;
-			datum = 0;
+		if (abs_pos < 0)		/* apparently out of partition */
 			break;
-		}
 
-		switch (get_notnull_info(winobj, abs_pos))
+		/* check NOT NULL cached info */
+		nn_info = get_notnull_info(winobj, abs_pos);
+		if (nn_info == NN_NOTNULL)	/* this row is known to be NOT NULL */
+			notnull_offset++;
+
+		else if (nn_info == NN_NULL)	/* this row is known to be NULL */
+			continue;			/* keep on moving forward or backward */
+
+		else					/* need to check NULL or not */
 		{
-			case NN_NOTNULL:	/* this row is known to be NOT NULL */
-				notnull_offset++;
-				if (notnull_offset >= notnull_relpos)
-				{
-					/* prepare to exit this loop */
-					datum = gettuple_eval_partition(winobj, argno,
-													abs_pos, isnull, isout);
-				}
-				break;
-			case NN_NULL:		/* this row is known to be NULL */
-				if (isout)
-					*isout = false;
-				*isnull = true;
-				datum = 0;
-				break;
-			default:			/* need to check NULL or not */
-				datum = gettuple_eval_partition(winobj, argno,
-												abs_pos, isnull, isout);
-				if (*isout)		/* out of partition? */
-					return datum;
-
-				if (!*isnull)
-					notnull_offset++;
-				/* record the row status */
-				put_notnull_info(winobj, abs_pos, *isnull);
+			/* get tupple and evaluate in a partition */
+			datum = gettuple_eval_partition(winobj, argno,
+											abs_pos, isnull, &myisout);
+			if (myisout)		/* out of partition? */
 				break;
+			if (!*isnull)
+				notnull_offset++;
+			/* record the row status */
+			put_notnull_info(winobj, abs_pos, *isnull);
 		}
 	} while (notnull_offset < notnull_relpos);
 
-	if (!*isout && set_mark)
+	/* get tupple and evaluate in a partition */
+	datum = gettuple_eval_partition(winobj, argno,
+									abs_pos, isnull, &myisout);
+	if (!myisout && set_mark)
 		WinSetMarkPosition(winobj, abs_pos);
+	if (isout)
+		*isout = myisout;
 
 	return datum;
 }
-- 
2.43.0

From 1a96b19b6f12c5a19ba11c9d4f5ea82f04733e39 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Fri, 10 Oct 2025 20:53:17 +0900
Subject: [PATCH v1] Allow multiple WinGetFuncArgInPartition/Frame calls with
 IGNORE NULLS option.

Previously it was assumed that there's only one call to
WinGetFuncArgInPartition/Frame in a window function when IGNORE NULLS
option is specified. To allow multiple calls to them,
winobj->notnull_info is modified from "uint8 *" to "uint8 **" so that
winobj->notnull_info could store pointers to not null info that
correspond to each function argument.
---
 src/backend/executor/nodeWindowAgg.c | 67 +++++++++++++++++-----------
 1 file changed, 42 insertions(+), 25 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..c7cb97a0643 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,7 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
-	uint8	   *notnull_info;	/* not null info */
+	uint8	  **notnull_info;	/* not null info for each func args */
 	int			num_notnull_info;	/* track size of the notnull_info array */
 
 	/*
@@ -214,10 +214,10 @@ static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 static Datum gettuple_eval_partition(WindowObject winobj, int argno,
 									 int64 abs_pos, bool *isnull,
 									 bool *isout);
-static void init_notnull_info(WindowObject winobj);
-static void grow_notnull_info(WindowObject winobj, int64 pos);
-static uint8 get_notnull_info(WindowObject winobj, int64 pos);
-static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+static void init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate);
+static void grow_notnull_info(WindowObject winobj, int64 pos, int argno);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos, int argno);
+static void put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull);
 
 /*
  * Not null info bit array consists of 2-bit items
@@ -1304,9 +1304,14 @@ begin_partition(WindowAggState *winstate)
 
 			/* reset null map */
 			if (winobj->ignore_nulls == IGNORE_NULLS)
-				memset(winobj->notnull_info, 0,
-					   NN_POS_TO_BYTES(
-									   perfuncstate->winobj->num_notnull_info));
+			{
+				int			numargs = perfuncstate->numArguments;
+
+				for (int j = 0; j < numargs; j++)
+					memset(winobj->notnull_info[j], 0,
+						   NN_POS_TO_BYTES(
+										   perfuncstate->winobj->num_notnull_info));
+			}
 		}
 	}
 
@@ -2734,7 +2739,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
 			winobj->ignore_nulls = wfunc->ignore_nulls;
-			init_notnull_info(winobj);
+			init_notnull_info(winobj, perfuncstate);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3386,7 +3391,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 		if (isout)
 			*isout = false;
 
-		v = get_notnull_info(winobj, abs_pos);
+		v = get_notnull_info(winobj, abs_pos, argno);
 		if (v == NN_NULL)		/* this row is known to be NULL */
 			goto advance;
 
@@ -3404,7 +3409,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 				notnull_offset++;
 
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 		else					/* this row is known to be NOT NULL */
 		{
@@ -3444,16 +3449,20 @@ out_of_frame:
  * Initialize non null map.
  */
 static void
-init_notnull_info(WindowObject winobj)
+init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate)
 {
 /* initial number of notnull info members */
 #define	INIT_NOT_NULL_INFO_NUM	128
+	int			numargs = perfuncstate->numArguments;
 
 	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 	{
 		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
 
-		winobj->notnull_info = palloc0(size);
+		winobj->notnull_info = palloc(sizeof(uint8 *) * numargs);
+		for (int i = 0; i < numargs; i++)
+			/* allocate notnull_info for each argument */
+			winobj->notnull_info[i] = palloc0(size);
 		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
 	}
 }
@@ -3462,9 +3471,10 @@ init_notnull_info(WindowObject winobj)
  * grow_notnull_info
  * expand notnull_info if necessary.
  * pos: not null info position
+ * argno: argument number
 */
 static void
-grow_notnull_info(WindowObject winobj, int64 pos)
+grow_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
 	if (pos >= winobj->num_notnull_info)
 	{
@@ -3473,8 +3483,8 @@ grow_notnull_info(WindowObject winobj, int64 pos)
 			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
 			Size		newsize = oldsize * 2;
 
-			winobj->notnull_info =
-				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->notnull_info[argno] =
+				repalloc0(winobj->notnull_info[argno], oldsize, newsize);
 			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
 			if (winobj->num_notnull_info > pos)
 				break;
@@ -3486,16 +3496,19 @@ grow_notnull_info(WindowObject winobj, int64 pos)
  * get_notnull_info
  * retrieve a map
  * pos: map position
+ * argno: argument number
  */
 static uint8
-get_notnull_info(WindowObject winobj, int64 pos)
+get_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
 }
 
@@ -3503,22 +3516,26 @@ get_notnull_info(WindowObject winobj, int64 pos)
  * put_notnull_info
  * update map
  * pos: map position
+ * argno: argument number
+ * isnull: indicate NULL or NOT
  */
 static void
-put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
 	int			shift;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	shift = NN_SHIFT(pos);
 	mb &= ~(NN_MASK << shift);	/* clear map */
 	mb |= (val << shift);		/* update map */
-	winobj->notnull_info[bpos] = mb;
+	mbp[bpos] = mb;
 }
 
 /***********************************************************************
@@ -3787,7 +3804,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 
 		/* check NOT NULL cached info */
-		nn_info = get_notnull_info(winobj, abs_pos);
+		nn_info = get_notnull_info(winobj, abs_pos, argno);
 		if (nn_info == NN_NOTNULL)	/* this row is known to be NOT NULL */
 			notnull_offset++;
 		else if (nn_info == NN_NULL)	/* this row is known to be NULL */
@@ -3802,7 +3819,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			if (!*isnull)
 				notnull_offset++;
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 	} while (notnull_offset < notnull_relpos);
 
-- 
2.43.0

From 61b4393bd12ad286e735a3bdf793443ecbf3b1aa Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sat, 11 Oct 2025 14:31:12 +0900
Subject: [PATCH v1] Use ereport rather than elog in
 WinCheckAndInitializeNullTreatment.

Previously WinCheckAndInitializeNullTreatment() used elog() to emit an
error message. ereport() should be used instead because it's a
user-facing error.

Also fix WinCheckAndInitializeNullTreatment() to use existing
get_func_name() to get a function's name, rather than own
implementation.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Author: Tatsuo Ishii <ishii@postgresql.org>
Discussion: https://postgr.es/m/2952409.1760023154%40sss.pgh.pa.us
---
 src/backend/executor/nodeWindowAgg.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..892bdbd5ef5 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -3540,22 +3540,15 @@ WinCheckAndInitializeNullTreatment(WindowObject winobj,
 {
 	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
 	{
-		HeapTuple	proctup;
-		Form_pg_proc procform;
-		Oid			funcid;
-
-		funcid = fcinfo->flinfo->fn_oid;
-		proctup = SearchSysCache1(PROCOID,
-								  ObjectIdGetDatum(funcid));
-		if (!HeapTupleIsValid(proctup))
-			elog(ERROR, "cache lookup failed for function %u", funcid);
-		procform = (Form_pg_proc) GETSTRUCT(proctup);
-		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
-			 NameStr(procform->proname));
+		char	   *funcname = get_func_name(fcinfo->flinfo->fn_oid);
+
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("function %s does not allow RESPECT/IGNORE NULLS",
+						funcname)));
 	}
 	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 		winobj->ignore_nulls = IGNORE_NULLS;
-
 }
 
 /*
-- 
2.43.0

From 925c527b4e776d49292a0fd747dcb16357418703 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sun, 12 Oct 2025 16:21:40 +0900
Subject: [PATCH v1] Allow window functions to accept a null treatment clause
 by default.

Previously window functions (either built-in or user defined) should
call WinCheckAndInitializeNullTreatment with allowNullTreatment==true
if they accept a null treatment clause (RESPECT NULLS/IGNORE
NULLS). Otherwise, they are called as if null treatment clause is not
specified.

This commit changes the behavior so that window functions accept a
null treatment clause as specified without calling
WinCheckAndInitializeNullTreatment.

If window functions do not want accept a null treatment clause, call
WinCheckAndInitializeNullTreatment with allowNullTreatment==false.
---
 src/backend/executor/nodeWindowAgg.c | 17 +++++++++++------
 src/backend/utils/adt/windowfuncs.c  |  4 ----
 2 files changed, 11 insertions(+), 10 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..c2e2ca69347 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1303,7 +1303,8 @@ begin_partition(WindowAggState *winstate)
 			winobj->seekpos = -1;
 
 			/* reset null map */
-			if (winobj->ignore_nulls == IGNORE_NULLS)
+			if (winobj->ignore_nulls == IGNORE_NULLS ||
+				winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 				memset(winobj->notnull_info, 0,
 					   NN_POS_TO_BYTES(
 									   perfuncstate->winobj->num_notnull_info));
@@ -3530,8 +3531,10 @@ put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
  * WinCheckAndInitializeNullTreatment
  *		Check null treatment clause and sets ignore_nulls
  *
- * Window functions should call this to check if they are being called with
- * a null treatment clause when they don't allow it, or to set ignore_nulls.
+ * Window functions call this if they do not accept a null treatment clause
+ * with allowNullTreatment==false. It's not mandatory but they can call this
+ * with allowNullTreatment==true to explicitly stat that they accept a a null
+ * treatment clause.
  */
 void
 WinCheckAndInitializeNullTreatment(WindowObject winobj,
@@ -3555,7 +3558,6 @@ WinCheckAndInitializeNullTreatment(WindowObject winobj,
 	}
 	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 		winobj->ignore_nulls = IGNORE_NULLS;
-
 }
 
 /*
@@ -3727,7 +3729,9 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	Assert(WindowObjectIsValid(winobj));
 	winstate = winobj->winstate;
 
-	null_treatment = (winobj->ignore_nulls == IGNORE_NULLS && relpos != 0);
+	null_treatment = ((winobj->ignore_nulls == IGNORE_NULLS ||
+					   winobj->ignore_nulls == PARSER_IGNORE_NULLS) &&
+					  relpos != 0);
 
 	switch (seektype)
 	{
@@ -3866,7 +3870,8 @@ WinGetFuncArgInFrame(WindowObject winobj, int argno,
 	econtext = winstate->ss.ps.ps_ExprContext;
 	slot = winstate->temp_slot_1;
 
-	if (winobj->ignore_nulls == IGNORE_NULLS)
+	if (winobj->ignore_nulls == IGNORE_NULLS ||
+		winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 		return ignorenulls_getfuncarginframe(winobj, argno, relpos, seektype,
 											 set_mark, isnull, isout);
 
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 969f02aa59b..7e936a8bfbc 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -541,7 +541,6 @@ leadlag_common(FunctionCallInfo fcinfo,
 	bool		isnull;
 	bool		isout;
 
-	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	if (withoffset)
 	{
 		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
@@ -659,7 +658,6 @@ window_first_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
-	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_HEAD, true,
 								  &isnull, NULL);
@@ -681,7 +679,6 @@ window_last_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		isnull;
 
-	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	result = WinGetFuncArgInFrame(winobj, 0,
 								  0, WINDOW_SEEK_TAIL, true,
 								  &isnull, NULL);
@@ -705,7 +702,6 @@ window_nth_value(PG_FUNCTION_ARGS)
 	bool		isnull;
 	int32		nth;
 
-	WinCheckAndInitializeNullTreatment(winobj, true, fcinfo);
 	nth = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
 	if (isnull)
 		PG_RETURN_NULL();
-- 
2.43.0

From 2913e8189adf9d75bdefef3c62ad83dabf2fa5cb Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 13 Oct 2025 13:39:04 +0900
Subject: [PATCH v2] Allow multiple WinGetFuncArgInPartition/Frame calls with
 IGNORE NULLS option.

Previously it was assumed that there's only one call to
WinGetFuncArgInPartition/Frame in a window function when IGNORE NULLS
option is specified. To allow multiple calls to them,
winobj->notnull_info is modified from "uint8 *" to "uint8 **" so that
winobj->notnull_info could store pointers to not null info that
correspond to each function argument.

Also fix the set mark position logic in WinGetFuncArgInPartition to
not raise a "cannot fetch row before WindowObject's mark position"
error in IGNORE NULLS case.
---
 src/backend/executor/nodeWindowAgg.c | 87 +++++++++++++++++++---------
 1 file changed, 61 insertions(+), 26 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..d25ab51ca82 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,7 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
-	uint8	   *notnull_info;	/* not null info */
+	uint8	  **notnull_info;	/* not null info for each func args */
 	int			num_notnull_info;	/* track size of the notnull_info array */
 
 	/*
@@ -214,10 +214,10 @@ static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 static Datum gettuple_eval_partition(WindowObject winobj, int argno,
 									 int64 abs_pos, bool *isnull,
 									 bool *isout);
-static void init_notnull_info(WindowObject winobj);
-static void grow_notnull_info(WindowObject winobj, int64 pos);
-static uint8 get_notnull_info(WindowObject winobj, int64 pos);
-static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+static void init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate);
+static void grow_notnull_info(WindowObject winobj, int64 pos, int argno);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos, int argno);
+static void put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull);
 
 /*
  * Not null info bit array consists of 2-bit items
@@ -1304,9 +1304,14 @@ begin_partition(WindowAggState *winstate)
 
 			/* reset null map */
 			if (winobj->ignore_nulls == IGNORE_NULLS)
-				memset(winobj->notnull_info, 0,
-					   NN_POS_TO_BYTES(
-									   perfuncstate->winobj->num_notnull_info));
+			{
+				int			numargs = perfuncstate->numArguments;
+
+				for (int j = 0; j < numargs; j++)
+					memset(winobj->notnull_info[j], 0,
+						   NN_POS_TO_BYTES(
+										   perfuncstate->winobj->num_notnull_info));
+			}
 		}
 	}
 
@@ -2734,7 +2739,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
 			winobj->ignore_nulls = wfunc->ignore_nulls;
-			init_notnull_info(winobj);
+			init_notnull_info(winobj, perfuncstate);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3386,7 +3391,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 		if (isout)
 			*isout = false;
 
-		v = get_notnull_info(winobj, abs_pos);
+		v = get_notnull_info(winobj, abs_pos, argno);
 		if (v == NN_NULL)		/* this row is known to be NULL */
 			goto advance;
 
@@ -3404,7 +3409,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 				notnull_offset++;
 
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 		else					/* this row is known to be NOT NULL */
 		{
@@ -3444,16 +3449,20 @@ out_of_frame:
  * Initialize non null map.
  */
 static void
-init_notnull_info(WindowObject winobj)
+init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate)
 {
 /* initial number of notnull info members */
 #define	INIT_NOT_NULL_INFO_NUM	128
+	int			numargs = perfuncstate->numArguments;
 
 	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 	{
 		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
 
-		winobj->notnull_info = palloc0(size);
+		winobj->notnull_info = palloc(sizeof(uint8 *) * numargs);
+		for (int i = 0; i < numargs; i++)
+			/* allocate notnull_info for each argument */
+			winobj->notnull_info[i] = palloc0(size);
 		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
 	}
 }
@@ -3462,9 +3471,10 @@ init_notnull_info(WindowObject winobj)
  * grow_notnull_info
  * expand notnull_info if necessary.
  * pos: not null info position
+ * argno: argument number
 */
 static void
-grow_notnull_info(WindowObject winobj, int64 pos)
+grow_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
 	if (pos >= winobj->num_notnull_info)
 	{
@@ -3473,8 +3483,8 @@ grow_notnull_info(WindowObject winobj, int64 pos)
 			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
 			Size		newsize = oldsize * 2;
 
-			winobj->notnull_info =
-				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->notnull_info[argno] =
+				repalloc0(winobj->notnull_info[argno], oldsize, newsize);
 			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
 			if (winobj->num_notnull_info > pos)
 				break;
@@ -3486,16 +3496,19 @@ grow_notnull_info(WindowObject winobj, int64 pos)
  * get_notnull_info
  * retrieve a map
  * pos: map position
+ * argno: argument number
  */
 static uint8
-get_notnull_info(WindowObject winobj, int64 pos)
+get_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
 }
 
@@ -3503,22 +3516,26 @@ get_notnull_info(WindowObject winobj, int64 pos)
  * put_notnull_info
  * update map
  * pos: map position
+ * argno: argument number
+ * isnull: indicate NULL or NOT
  */
 static void
-put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
 	int			shift;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	shift = NN_SHIFT(pos);
 	mb &= ~(NN_MASK << shift);	/* clear map */
 	mb |= (val << shift);		/* update map */
-	winobj->notnull_info[bpos] = mb;
+	mbp[bpos] = mb;
 }
 
 /***********************************************************************
@@ -3717,6 +3734,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 {
 	WindowAggState *winstate;
 	int64		abs_pos;
+	int64		mark_pos;
 	Datum		datum;
 	bool		null_treatment;
 	int			notnull_offset;
@@ -3772,6 +3790,23 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	forward = relpos > 0 ? 1 : -1;
 	myisout = false;
 	datum = 0;
+	/*
+	 * IGNORE NULLS + WINDOW_SEEK_CURRENT + relpos > 0 case, we would fetch
+	 * beyond the current row + relpos to find out the target row. If we mark
+	 * at abs_pos, next call to WinGetFuncArgInPartition or
+	 * WinGetFuncArgInFrame (in case when a window function have multiple
+	 * args) could fail with "cannot fetch row before WindowObject's mark
+	 * position". So keep the mark position at currentpos.
+	*/
+	if (seektype == WINDOW_SEEK_CURRENT &&	relpos > 0)
+		mark_pos = winstate->currentpos;
+	else
+		/*
+		 * For other cases we have no idea what position of row callers would
+		 * fetch next time. Also for relpos < 0 case (we go backward), we
+		 * cannot set mark either. For those cases we always set mark at 0.
+		 */
+		mark_pos = 0;
 
 	/*
 	 * Get the next nonnull value in the partition, moving forward or backward
@@ -3787,7 +3822,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 
 		/* check NOT NULL cached info */
-		nn_info = get_notnull_info(winobj, abs_pos);
+		nn_info = get_notnull_info(winobj, abs_pos, argno);
 		if (nn_info == NN_NOTNULL)	/* this row is known to be NOT NULL */
 			notnull_offset++;
 		else if (nn_info == NN_NULL)	/* this row is known to be NULL */
@@ -3802,7 +3837,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			if (!*isnull)
 				notnull_offset++;
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 	} while (notnull_offset < notnull_relpos);
 
@@ -3810,7 +3845,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	datum = gettuple_eval_partition(winobj, argno,
 									abs_pos, isnull, &myisout);
 	if (!myisout && set_mark)
-		WinSetMarkPosition(winobj, abs_pos);
+		WinSetMarkPosition(winobj, mark_pos);
 	if (isout)
 		*isout = myisout;
 
-- 
2.43.0

From 692f7d8b6c82cc76a7a9915f3adcca00fa1fd9ba Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 13 Oct 2025 13:48:54 +0900
Subject: [PATCH v2] Allow multiple WinGetFuncArgInPartition/Frame calls with
 IGNORE NULLS option.

Previously it was assumed that there's only one call to
WinGetFuncArgInPartition/Frame in a window function when IGNORE NULLS
option is specified. To allow multiple calls to them,
winobj->notnull_info is modified from "uint8 *" to "uint8 **" so that
winobj->notnull_info could store pointers to not null info that
correspond to each function argument.

Also fix the set mark position logic in WinGetFuncArgInPartition to
not raise a "cannot fetch row before WindowObject's mark position"
error in IGNORE NULLS case.
---
 src/backend/executor/nodeWindowAgg.c | 87 +++++++++++++++++++---------
 1 file changed, 61 insertions(+), 26 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..d25ab51ca82 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,7 +69,7 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
-	uint8	   *notnull_info;	/* not null info */
+	uint8	  **notnull_info;	/* not null info for each func args */
 	int			num_notnull_info;	/* track size of the notnull_info array */
 
 	/*
@@ -214,10 +214,10 @@ static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 static Datum gettuple_eval_partition(WindowObject winobj, int argno,
 									 int64 abs_pos, bool *isnull,
 									 bool *isout);
-static void init_notnull_info(WindowObject winobj);
-static void grow_notnull_info(WindowObject winobj, int64 pos);
-static uint8 get_notnull_info(WindowObject winobj, int64 pos);
-static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+static void init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate);
+static void grow_notnull_info(WindowObject winobj, int64 pos, int argno);
+static uint8 get_notnull_info(WindowObject winobj, int64 pos, int argno);
+static void put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull);
 
 /*
  * Not null info bit array consists of 2-bit items
@@ -1304,9 +1304,14 @@ begin_partition(WindowAggState *winstate)
 
 			/* reset null map */
 			if (winobj->ignore_nulls == IGNORE_NULLS)
-				memset(winobj->notnull_info, 0,
-					   NN_POS_TO_BYTES(
-									   perfuncstate->winobj->num_notnull_info));
+			{
+				int			numargs = perfuncstate->numArguments;
+
+				for (int j = 0; j < numargs; j++)
+					memset(winobj->notnull_info[j], 0,
+						   NN_POS_TO_BYTES(
+										   perfuncstate->winobj->num_notnull_info));
+			}
 		}
 	}
 
@@ -2734,7 +2739,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
 			winobj->ignore_nulls = wfunc->ignore_nulls;
-			init_notnull_info(winobj);
+			init_notnull_info(winobj, perfuncstate);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3386,7 +3391,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 		if (isout)
 			*isout = false;
 
-		v = get_notnull_info(winobj, abs_pos);
+		v = get_notnull_info(winobj, abs_pos, argno);
 		if (v == NN_NULL)		/* this row is known to be NULL */
 			goto advance;
 
@@ -3404,7 +3409,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 				notnull_offset++;
 
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 		else					/* this row is known to be NOT NULL */
 		{
@@ -3444,16 +3449,20 @@ out_of_frame:
  * Initialize non null map.
  */
 static void
-init_notnull_info(WindowObject winobj)
+init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate)
 {
 /* initial number of notnull info members */
 #define	INIT_NOT_NULL_INFO_NUM	128
+	int			numargs = perfuncstate->numArguments;
 
 	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 	{
 		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
 
-		winobj->notnull_info = palloc0(size);
+		winobj->notnull_info = palloc(sizeof(uint8 *) * numargs);
+		for (int i = 0; i < numargs; i++)
+			/* allocate notnull_info for each argument */
+			winobj->notnull_info[i] = palloc0(size);
 		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
 	}
 }
@@ -3462,9 +3471,10 @@ init_notnull_info(WindowObject winobj)
  * grow_notnull_info
  * expand notnull_info if necessary.
  * pos: not null info position
+ * argno: argument number
 */
 static void
-grow_notnull_info(WindowObject winobj, int64 pos)
+grow_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
 	if (pos >= winobj->num_notnull_info)
 	{
@@ -3473,8 +3483,8 @@ grow_notnull_info(WindowObject winobj, int64 pos)
 			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
 			Size		newsize = oldsize * 2;
 
-			winobj->notnull_info =
-				repalloc0(winobj->notnull_info, oldsize, newsize);
+			winobj->notnull_info[argno] =
+				repalloc0(winobj->notnull_info[argno], oldsize, newsize);
 			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
 			if (winobj->num_notnull_info > pos)
 				break;
@@ -3486,16 +3496,19 @@ grow_notnull_info(WindowObject winobj, int64 pos)
  * get_notnull_info
  * retrieve a map
  * pos: map position
+ * argno: argument number
  */
 static uint8
-get_notnull_info(WindowObject winobj, int64 pos)
+get_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
 }
 
@@ -3503,22 +3516,26 @@ get_notnull_info(WindowObject winobj, int64 pos)
  * put_notnull_info
  * update map
  * pos: map position
+ * argno: argument number
+ * isnull: indicate NULL or NOT
  */
 static void
-put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
 	int			shift;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	shift = NN_SHIFT(pos);
 	mb &= ~(NN_MASK << shift);	/* clear map */
 	mb |= (val << shift);		/* update map */
-	winobj->notnull_info[bpos] = mb;
+	mbp[bpos] = mb;
 }
 
 /***********************************************************************
@@ -3717,6 +3734,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 {
 	WindowAggState *winstate;
 	int64		abs_pos;
+	int64		mark_pos;
 	Datum		datum;
 	bool		null_treatment;
 	int			notnull_offset;
@@ -3772,6 +3790,23 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	forward = relpos > 0 ? 1 : -1;
 	myisout = false;
 	datum = 0;
+	/*
+	 * IGNORE NULLS + WINDOW_SEEK_CURRENT + relpos > 0 case, we would fetch
+	 * beyond the current row + relpos to find out the target row. If we mark
+	 * at abs_pos, next call to WinGetFuncArgInPartition or
+	 * WinGetFuncArgInFrame (in case when a window function have multiple
+	 * args) could fail with "cannot fetch row before WindowObject's mark
+	 * position". So keep the mark position at currentpos.
+	*/
+	if (seektype == WINDOW_SEEK_CURRENT &&	relpos > 0)
+		mark_pos = winstate->currentpos;
+	else
+		/*
+		 * For other cases we have no idea what position of row callers would
+		 * fetch next time. Also for relpos < 0 case (we go backward), we
+		 * cannot set mark either. For those cases we always set mark at 0.
+		 */
+		mark_pos = 0;
 
 	/*
 	 * Get the next nonnull value in the partition, moving forward or backward
@@ -3787,7 +3822,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 
 		/* check NOT NULL cached info */
-		nn_info = get_notnull_info(winobj, abs_pos);
+		nn_info = get_notnull_info(winobj, abs_pos, argno);
 		if (nn_info == NN_NOTNULL)	/* this row is known to be NOT NULL */
 			notnull_offset++;
 		else if (nn_info == NN_NULL)	/* this row is known to be NULL */
@@ -3802,7 +3837,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			if (!*isnull)
 				notnull_offset++;
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 	} while (notnull_offset < notnull_relpos);
 
@@ -3810,7 +3845,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	datum = gettuple_eval_partition(winobj, argno,
 									abs_pos, isnull, &myisout);
 	if (!myisout && set_mark)
-		WinSetMarkPosition(winobj, abs_pos);
+		WinSetMarkPosition(winobj, mark_pos);
 	if (isout)
 		*isout = myisout;
 
-- 
2.43.0

From 976de4af0951a49e9fa55fad03f0582a4e77e7f5 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Mon, 13 Oct 2025 14:32:01 +0900
Subject: [PATCH v2] Use ereport rather than elog in
 WinCheckAndInitializeNullTreatment.

Previously WinCheckAndInitializeNullTreatment() used elog() to emit an
error message. ereport() should be used instead because it's a
user-facing error. Also use existing get_func_name() to get a
function's name, rather than own implementation.

In addition to them, add an assertion to validate winobj parameter,
just like other window function API.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Author: Tatsuo Ishii <ishii@postgresql.org>
Reviewed-by: Chao Li <lic@highgo.com>
Discussion: https://postgr.es/m/2952409.1760023154%40sss.pgh.pa.us
---
 src/backend/executor/nodeWindowAgg.c | 20 ++++++++------------
 1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index e6a53f95391..47e00be7b49 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -3538,24 +3538,20 @@ WinCheckAndInitializeNullTreatment(WindowObject winobj,
 								   bool allowNullTreatment,
 								   FunctionCallInfo fcinfo)
 {
+	Assert(WindowObjectIsValid(winobj));
 	if (winobj->ignore_nulls != NO_NULLTREATMENT && !allowNullTreatment)
 	{
-		HeapTuple	proctup;
-		Form_pg_proc procform;
-		Oid			funcid;
+		const char *funcname = get_func_name(fcinfo->flinfo->fn_oid);
 
-		funcid = fcinfo->flinfo->fn_oid;
-		proctup = SearchSysCache1(PROCOID,
-								  ObjectIdGetDatum(funcid));
-		if (!HeapTupleIsValid(proctup))
-			elog(ERROR, "cache lookup failed for function %u", funcid);
-		procform = (Form_pg_proc) GETSTRUCT(proctup);
-		elog(ERROR, "function %s does not allow RESPECT/IGNORE NULLS",
-			 NameStr(procform->proname));
+		if (!funcname)
+			elog(ERROR, "could not get function name");
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("function %s does not allow RESPECT/IGNORE NULLS",
+						funcname)));
 	}
 	else if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 		winobj->ignore_nulls = IGNORE_NULLS;
-
 }
 
 /*
-- 
2.43.0

From c18dcbccff7bd7c95295beedabb2116cbb3b3be2 Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Thu, 16 Oct 2025 19:00:56 +0900
Subject: [PATCH v1] Fix coverity complaint about WinGetFuncArgInPartition.

Coverity complains that the return value from gettuple_eval_partition
in a do..while loop in WinGetFuncArgInPartition is overwritten when
exiting the while loop. This commit tries to fix the issue by changing
gettuple_eval_partition call to:

(void) gettuple_eval_partition()

explicitly stating that we discard the return value.

Also enhance some comments for easier code reading.

Discussion: https://postgr.es/m/aPCOabSE4VfJLaky%40paquier.xyz
---
 src/backend/executor/nodeWindowAgg.c | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 47e00be7b49..aa145d4e1a9 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -3270,8 +3270,9 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
 	return true;
 }
 
-/*
- * get tuple and evaluate in partition
+/* gettuple_eval_partition
+ * get tuple in a patition and evaluate the window function's argument
+ * expression on it.
  */
 static Datum
 gettuple_eval_partition(WindowObject winobj, int argno,
@@ -3790,9 +3791,15 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			continue;			/* keep on moving forward or backward */
 		else					/* need to check NULL or not */
 		{
-			/* get tuple and evaluate in partition */
-			datum = gettuple_eval_partition(winobj, argno,
-											abs_pos, isnull, &myisout);
+			/*
+			 * NOT NULL info does not exist yet.  Get tuple and evaluate func
+			 * arg in partition. We ignore the return value from
+			 * gettuple_eval_partition because we are just interested in
+			 * whether we are inside or outside of partition, NULL or NOT
+			 * NULL.
+			 */
+			(void) gettuple_eval_partition(winobj, argno,
+										   abs_pos, isnull, &myisout);
 			if (myisout)		/* out of partition? */
 				break;
 			if (!*isnull)
@@ -3802,7 +3809,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 		}
 	} while (notnull_offset < notnull_relpos);
 
-	/* get tuple and evaluate in partition */
+	/* get tuple and evaluate func arg in partition */
 	datum = gettuple_eval_partition(winobj, argno,
 									abs_pos, isnull, &myisout);
 	if (!myisout && set_mark)
-- 
2.43.0

From 888dc5db9e8a8c0bb4b9b1603e5335f209c2d98c Mon Sep 17 00:00:00 2001
From: Tatsuo Ishii <ishii@postgresql.org>
Date: Sun, 19 Oct 2025 18:37:08 +0900
Subject: [PATCH v3] Fix multi WinGetFuncArgInFrame/Partition calls with IGNORE
 NULLS.

Previously it was mistakenly assumed that there's only one window
function argument which needs to be processed by WinGetFuncArgInFrame
or WinGetFuncArgInPartition when IGNORE NULLS option is specified. To
eliminate the limitation, WindowObject->notnull_info is modified from
"uint8 *" to "uint8 **" so that WindowObject->notnull_info could store
pointers to "uint8 *" which holds NOT NULL info corresponding to each
window function argument. Moreover, WindowObject->num_notnull_info is
changed from "int" to "int64 *" so that WindowObject->num_notnull_info
could store the number of NOT NULL info corresponding to each function
argument. Memories for these data structures will be allocated when
WinGetFuncArgInFrame or WinGetFuncArgInPartition is called. Thus no
memory except the pointers is allocated for function arguments which
do not call these functions

Also fix the set mark position logic in WinGetFuncArgInPartition to
not raise a "cannot fetch row before WindowObject's mark position"
error in IGNORE NULLS case.

Reported-by: Tom Lane <tgl@sss.pgh.pa.us>
Author: Tatsuo Ishii <ishii@postgresql.org>
Discussion: https://postgr.es/m/2952409.1760023154%40sss.pgh.pa.us
---
 src/backend/executor/nodeWindowAgg.c | 136 +++++++++++++++++++--------
 1 file changed, 98 insertions(+), 38 deletions(-)

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index aa145d4e1a9..497eb25ea29 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -69,8 +69,10 @@ typedef struct WindowObjectData
 	int			readptr;		/* tuplestore read pointer for this fn */
 	int64		markpos;		/* row that markptr is positioned on */
 	int64		seekpos;		/* row that readptr is positioned on */
-	uint8	   *notnull_info;	/* not null info */
-	int			num_notnull_info;	/* track size of the notnull_info array */
+	uint8	  **notnull_info;	/* not null info for each func args */
+	int64	   *num_notnull_info;	/* track size (number of tuples in
+									 * partition) of the notnull_info array
+									 * for each func args */
 
 	/*
 	 * Null treatment options. One of: NO_NULLTREATMENT, PARSER_IGNORE_NULLS,
@@ -214,10 +216,14 @@ static Datum ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 static Datum gettuple_eval_partition(WindowObject winobj, int argno,
 									 int64 abs_pos, bool *isnull,
 									 bool *isout);
-static void init_notnull_info(WindowObject winobj);
-static void grow_notnull_info(WindowObject winobj, int64 pos);
-static uint8 get_notnull_info(WindowObject winobj, int64 pos);
-static void put_notnull_info(WindowObject winobj, int64 pos, bool isnull);
+static void init_notnull_info(WindowObject winobj,
+							  WindowStatePerFunc perfuncstate);
+static void grow_notnull_info(WindowObject winobj,
+							  int64 pos, int argno);
+static uint8 get_notnull_info(WindowObject winobj,
+							  int64 pos, int argno);
+static void put_notnull_info(WindowObject winobj,
+							 int64 pos, int argno, bool isnull);
 
 /*
  * Not null info bit array consists of 2-bit items
@@ -1303,10 +1309,20 @@ begin_partition(WindowAggState *winstate)
 			winobj->seekpos = -1;
 
 			/* reset null map */
-			if (winobj->ignore_nulls == IGNORE_NULLS)
-				memset(winobj->notnull_info, 0,
-					   NN_POS_TO_BYTES(
-									   perfuncstate->winobj->num_notnull_info));
+			if (winobj->ignore_nulls == IGNORE_NULLS ||
+				winobj->ignore_nulls == PARSER_IGNORE_NULLS)
+			{
+				int			numargs = perfuncstate->numArguments;
+
+				for (int j = 0; j < numargs; j++)
+				{
+					int			n = winobj->num_notnull_info[j];
+
+					if (n > 0)
+						memset(winobj->notnull_info[j], 0,
+							   NN_POS_TO_BYTES(n));
+				}
+			}
 		}
 	}
 
@@ -2734,7 +2750,7 @@ ExecInitWindowAgg(WindowAgg *node, EState *estate, int eflags)
 			winobj->localmem = NULL;
 			perfuncstate->winobj = winobj;
 			winobj->ignore_nulls = wfunc->ignore_nulls;
-			init_notnull_info(winobj);
+			init_notnull_info(winobj, perfuncstate);
 
 			/* It's a real window function, so set up to call it. */
 			fmgr_info_cxt(wfunc->winfnoid, &perfuncstate->flinfo,
@@ -3387,7 +3403,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 		if (isout)
 			*isout = false;
 
-		v = get_notnull_info(winobj, abs_pos);
+		v = get_notnull_info(winobj, abs_pos, argno);
 		if (v == NN_NULL)		/* this row is known to be NULL */
 			goto advance;
 
@@ -3405,7 +3421,7 @@ ignorenulls_getfuncarginframe(WindowObject winobj, int argno,
 				notnull_offset++;
 
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 		else					/* this row is known to be NOT NULL */
 		{
@@ -3445,17 +3461,14 @@ out_of_frame:
  * Initialize non null map.
  */
 static void
-init_notnull_info(WindowObject winobj)
+init_notnull_info(WindowObject winobj, WindowStatePerFunc perfuncstate)
 {
-/* initial number of notnull info members */
-#define	INIT_NOT_NULL_INFO_NUM	128
+	int			numargs = perfuncstate->numArguments;
 
 	if (winobj->ignore_nulls == PARSER_IGNORE_NULLS)
 	{
-		Size		size = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
-
-		winobj->notnull_info = palloc0(size);
-		winobj->num_notnull_info = INIT_NOT_NULL_INFO_NUM;
+		winobj->notnull_info = palloc0(sizeof(uint8 *) * numargs);
+		winobj->num_notnull_info = palloc0(sizeof(int64) * numargs);
 	}
 }
 
@@ -3463,23 +3476,43 @@ init_notnull_info(WindowObject winobj)
  * grow_notnull_info
  * expand notnull_info if necessary.
  * pos: not null info position
+ * argno: argument number
 */
 static void
-grow_notnull_info(WindowObject winobj, int64 pos)
+grow_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
-	if (pos >= winobj->num_notnull_info)
+/* initial number of notnull info members */
+#define	INIT_NOT_NULL_INFO_NUM	128
+
+	if (pos >= winobj->num_notnull_info[argno])
 	{
+		/* We may be called in a short-lived context */
+		MemoryContext oldcontext = MemoryContextSwitchTo
+			(winobj->winstate->ss.ps.ps_ExprContext->ecxt_per_query_memory);
+
 		for (;;)
 		{
-			Size		oldsize = NN_POS_TO_BYTES(winobj->num_notnull_info);
-			Size		newsize = oldsize * 2;
+			Size		oldsize = NN_POS_TO_BYTES
+				(winobj->num_notnull_info[argno]);
+			Size		newsize;
 
-			winobj->notnull_info =
-				repalloc0(winobj->notnull_info, oldsize, newsize);
-			winobj->num_notnull_info = NN_BYTES_TO_POS(newsize);
-			if (winobj->num_notnull_info > pos)
+			if (oldsize == 0)	/* memory has not been allocated yet for this
+								 * arg */
+			{
+				newsize = NN_POS_TO_BYTES(INIT_NOT_NULL_INFO_NUM);
+				winobj->notnull_info[argno] = palloc0(newsize);
+			}
+			else
+			{
+				newsize = oldsize * 2;
+				winobj->notnull_info[argno] =
+					repalloc0(winobj->notnull_info[argno], oldsize, newsize);
+			}
+			winobj->num_notnull_info[argno] = NN_BYTES_TO_POS(newsize);
+			if (winobj->num_notnull_info[argno] > pos)
 				break;
 		}
+		MemoryContextSwitchTo(oldcontext);
 	}
 }
 
@@ -3487,16 +3520,19 @@ grow_notnull_info(WindowObject winobj, int64 pos)
  * get_notnull_info
  * retrieve a map
  * pos: map position
+ * argno: argument number
  */
 static uint8
-get_notnull_info(WindowObject winobj, int64 pos)
+get_notnull_info(WindowObject winobj, int64 pos, int argno)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	return (mb >> (NN_SHIFT(pos))) & NN_MASK;
 }
 
@@ -3504,22 +3540,26 @@ get_notnull_info(WindowObject winobj, int64 pos)
  * put_notnull_info
  * update map
  * pos: map position
+ * argno: argument number
+ * isnull: indicate NULL or NOT
  */
 static void
-put_notnull_info(WindowObject winobj, int64 pos, bool isnull)
+put_notnull_info(WindowObject winobj, int64 pos, int argno, bool isnull)
 {
+	uint8	   *mbp;
 	uint8		mb;
 	int64		bpos;
 	uint8		val = isnull ? NN_NULL : NN_NOTNULL;
 	int			shift;
 
-	grow_notnull_info(winobj, pos);
+	grow_notnull_info(winobj, pos, argno);
 	bpos = NN_POS_TO_BYTES(pos);
-	mb = winobj->notnull_info[bpos];
+	mbp = winobj->notnull_info[argno];
+	mb = mbp[bpos];
 	shift = NN_SHIFT(pos);
 	mb &= ~(NN_MASK << shift);	/* clear map */
 	mb |= (val << shift);		/* update map */
-	winobj->notnull_info[bpos] = mb;
+	mbp[bpos] = mb;
 }
 
 /***********************************************************************
@@ -3714,6 +3754,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 {
 	WindowAggState *winstate;
 	int64		abs_pos;
+	int64		mark_pos;
 	Datum		datum;
 	bool		null_treatment;
 	int			notnull_offset;
@@ -3770,6 +3811,25 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	myisout = false;
 	datum = 0;
 
+	/*
+	 * IGNORE NULLS + WINDOW_SEEK_CURRENT + relpos > 0 case, we would fetch
+	 * beyond the current row + relpos to find out the target row. If we mark
+	 * at abs_pos, next call to WinGetFuncArgInPartition or
+	 * WinGetFuncArgInFrame (in case when a window function have multiple
+	 * args) could fail with "cannot fetch row before WindowObject's mark
+	 * position". So keep the mark position at currentpos.
+	 */
+	if (seektype == WINDOW_SEEK_CURRENT && relpos > 0)
+		mark_pos = winstate->currentpos;
+	else
+
+		/*
+		 * For other cases we have no idea what position of row callers would
+		 * fetch next time. Also for relpos < 0 case (we go backward), we
+		 * cannot set mark either. For those cases we always set mark at 0.
+		 */
+		mark_pos = 0;
+
 	/*
 	 * Get the next nonnull value in the partition, moving forward or backward
 	 * until we find a value or reach the partition's end.  We cache the
@@ -3784,7 +3844,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			break;
 
 		/* check NOT NULL cached info */
-		nn_info = get_notnull_info(winobj, abs_pos);
+		nn_info = get_notnull_info(winobj, abs_pos, argno);
 		if (nn_info == NN_NOTNULL)	/* this row is known to be NOT NULL */
 			notnull_offset++;
 		else if (nn_info == NN_NULL)	/* this row is known to be NULL */
@@ -3805,7 +3865,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 			if (!*isnull)
 				notnull_offset++;
 			/* record the row status */
-			put_notnull_info(winobj, abs_pos, *isnull);
+			put_notnull_info(winobj, abs_pos, argno, *isnull);
 		}
 	} while (notnull_offset < notnull_relpos);
 
@@ -3813,7 +3873,7 @@ WinGetFuncArgInPartition(WindowObject winobj, int argno,
 	datum = gettuple_eval_partition(winobj, argno,
 									abs_pos, isnull, &myisout);
 	if (!myisout && set_mark)
-		WinSetMarkPosition(winobj, abs_pos);
+		WinSetMarkPosition(winobj, mark_pos);
 	if (isout)
 		*isout = myisout;
 
-- 
2.43.0