Request for Patch Feedback: Lag & Lead Window Functions Can Ignore Nulls

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 896c08c..75cb36e 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12003,6 +12003,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12017,7 +12018,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12030,6 +12034,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12044,7 +12049,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12138,11 +12145,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 3bc42ba..548c506 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1996,6 +1996,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9d07f30..6dda644 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -496,6 +496,7 @@ 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
+				over_specification
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 
@@ -551,7 +552,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -581,7 +582,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -615,6 +616,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * creates these tokens when required.
  */
 %token			NULLS_FIRST NULLS_LAST WITH_TIME
+%token			RESPECT_NULLS IGNORE_NULLS
 
 
 /* Precedence: lowest to highest */
@@ -11785,7 +11787,8 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
+over_specification:
+			  OVER window_specification
 				{ $$ = $2; }
 			| OVER ColId
 				{
@@ -11800,6 +11803,18 @@ over_clause: OVER window_specification
 					n->location = @2;
 					$$ = n;
 				}
+			;
+
+over_clause: over_specification
+				{ $$ = $1; }
+			| RESPECT_NULLS over_specification
+				{ $$ = $2; }
+			| IGNORE_NULLS over_specification
+				{
+					if($2)
+						$2->frameOptions |= FRAMEOPTION_IGNORE_NULLS;
+					$$ = $2;
+				}	
 			| /*EMPTY*/
 				{ $$ = NULL; }
 		;
@@ -12765,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12852,6 +12868,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index b8ec790..25d09e0 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -156,6 +156,33 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 2f171ac..3144fd7 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -292,6 +292,7 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
 
 	if (withoffset)
 	{
@@ -322,8 +323,29 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
+	if(ignore_nulls)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us.
+		 */
+		Datum* stash = (Datum*) WinGetPartitionLocalMemory(winobj, sizeof(Datum));
+		if(isnull)
+		{
+			result = *stash;
+			isnull = result == 0;
+		}
+		else
+		{
+			*stash = result;
+		}
+	}
+
 	if (isnull)
+	{
 		PG_RETURN_NULL();
+	}
 
 	PG_RETURN_DATUM(result);
 }
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2229ef0..a13c58b 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000 /* lead/lag/nth */
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index f4b51d6..fe5dcb3 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -45,6 +45,8 @@ my %replace_string = (
 	'WITH_TIME'    => 'with time',
 	'NULLS_FIRST'  => 'nulls first',
 	'NULLS_LAST'   => 'nulls last',
+	'RESPECT_NULLS'  => 'respect nulls',
+	'IGNORE_NULLS'   => 'ignore nulls',
 	'TYPECAST'     => '::',
 	'DOT_DOT'      => '..',
 	'COLON_EQUALS' => ':=',);
diff --git a/src/interfaces/ecpg/preproc/parser.c b/src/interfaces/ecpg/preproc/parser.c
index 2ce9dd9..53f4167 100644
--- a/src/interfaces/ecpg/preproc/parser.c
+++ b/src/interfaces/ecpg/preproc/parser.c
@@ -121,6 +121,53 @@ filtered_base_yylex(void)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..bcc9140 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,20 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null),
+('sales', 1, 5000, '2006-10-01', null),
+('personnel', 5, 3500, '2007-12-10', null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22'),
+('personnel', 2, 3900, '2006-12-23', null),
+('develop', 7, 4200, '2008-01-01', null),
+('develop', 9, 4500, '2008-01-01', null),
+('sales', 3, 4800, '2007-08-01', '2009-03-05'),
+('develop', 8, 6000, '2006-10-01', '2009-11-17'),
+('develop', 11, 5200, '2007-08-15', null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1021,96 @@ 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
+-- test null behaviour
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..cc9b583 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null),
+('sales', 1, 5000, '2006-10-01', null),
+('personnel', 5, 3500, '2007-12-10', null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22'),
+('personnel', 2, 3900, '2006-12-23', null),
+('develop', 7, 4200, '2008-01-01', null),
+('develop', 9, 4500, '2008-01-01', null),
+('sales', 3, 4800, '2007-08-01', '2009-03-05'),
+('develop', 8, 6000, '2006-10-01', '2009-11-17'),
+('develop', 11, 5200, '2007-08-15', null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +265,18 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;

diff --git a/src/.DS_Store b/src/.DS_Store
new file mode 100644
index 0000000..535a8dc
Binary files /dev/null and b/src/.DS_Store differ
diff --git a/src/backend/.DS_Store b/src/backend/.DS_Store
new file mode 100644
index 0000000..327792b
Binary files /dev/null and b/src/backend/.DS_Store differ
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 3bc42ba..eb42901 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1986,6 +1986,40 @@ WinGetPartitionLocalMemory(WindowObject winobj, Size sz)
 }
 
 /*
+ * WinGetResultDatumCopy
+ *		Gets a copy of the given datum.
+ *
+ * This uses the window's per-function ByVal and TypeLen information
+ * when copying the datum.
+ */
+Datum
+WinGetResultDatumCopy(WindowObject winobj, Datum datum)
+{
+	WindowStatePerFunc perfunc;
+
+	Assert(WindowObjectIsValid(winobj));
+	perfunc = winobj->winstate->perfunc;
+	return datumCopy(datum, perfunc->resulttypeByVal, perfunc->resulttypeLen);
+}
+
+/*
+ * WinFreeResultDatumCopy
+ *		Frees a Datum previously created by WinGetResultDatumCopy.
+ *
+ * This uses the window's per-function ByVal and TypeLen information
+ * when copying the datum.
+ */
+void
+WinFreeResultDatumCopy(WindowObject winobj, Datum datum)
+{
+	WindowStatePerFunc perfunc;
+
+	Assert(WindowObjectIsValid(winobj));
+	perfunc = winobj->winstate->perfunc;
+	datumFree(datum, perfunc->resulttypeByVal, perfunc->resulttypeLen);
+}
+
+/*
  * WinGetCurrentPosition
  *		Return the current row's position (counting from 0) within the current
  *		partition.
@@ -1996,6 +2030,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 9d07f30..6dda644 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -496,6 +496,7 @@ 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
+				over_specification
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 
@@ -551,7 +552,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -581,7 +582,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -615,6 +616,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * creates these tokens when required.
  */
 %token			NULLS_FIRST NULLS_LAST WITH_TIME
+%token			RESPECT_NULLS IGNORE_NULLS
 
 
 /* Precedence: lowest to highest */
@@ -11785,7 +11787,8 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
+over_specification:
+			  OVER window_specification
 				{ $$ = $2; }
 			| OVER ColId
 				{
@@ -11800,6 +11803,18 @@ over_clause: OVER window_specification
 					n->location = @2;
 					$$ = n;
 				}
+			;
+
+over_clause: over_specification
+				{ $$ = $1; }
+			| RESPECT_NULLS over_specification
+				{ $$ = $2; }
+			| IGNORE_NULLS over_specification
+				{
+					if($2)
+						$2->frameOptions |= FRAMEOPTION_IGNORE_NULLS;
+					$$ = $2;
+				}	
 			| /*EMPTY*/
 				{ $$ = NULL; }
 		;
@@ -12765,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12852,6 +12868,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index b8ec790..25d09e0 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -156,6 +156,33 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/backend/utils/.DS_Store b/src/backend/utils/.DS_Store
new file mode 100644
index 0000000..cbbea58
Binary files /dev/null and b/src/backend/utils/.DS_Store differ
diff --git a/src/backend/utils/adt/datum.c b/src/backend/utils/adt/datum.c
index 612b7ef..e72f5a9 100644
--- a/src/backend/utils/adt/datum.c
+++ b/src/backend/utils/adt/datum.c
@@ -129,7 +129,7 @@ datumCopy(Datum value, bool typByVal, int typLen)
 		realSize = datumGetSize(value, typByVal, typLen);
 
 		s = (char *) palloc(realSize);
-		memcpy(s, DatumGetPointer(value), realSize);
+		memcpy(s, 	(value), realSize);
 		res = PointerGetDatum(s);
 	}
 	return res;
@@ -144,7 +144,6 @@ datumCopy(Datum value, bool typByVal, int typLen)
  * ONLY datums created by "datumCopy" can be freed!
  *-------------------------------------------------------------------------
  */
-#ifdef NOT_USED
 void
 datumFree(Datum value, bool typByVal, int typLen)
 {
@@ -155,7 +154,6 @@ datumFree(Datum value, bool typByVal, int typLen)
 		pfree(s);
 	}
 }
-#endif
 
 /*-------------------------------------------------------------------------
  * datumIsEqual
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 2f171ac..fea772f 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -25,6 +25,15 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * structure for IGNORE NULLS / RESPECT NULLS semantics
+ */
+typedef struct leadlag_context
+{
+	Datum		last;			/* last non-null result */
+	bool		last_isnull;
+} leadlag_context;
+
+/*
  * ntile process information
  */
 typedef struct
@@ -292,6 +301,8 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
+	leadlag_context* context;
 
 	if (withoffset)
 	{
@@ -322,8 +333,47 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
+	if(ignore_nulls)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us. 
+		 */
+		context = (leadlag_context *) 
+			WinGetPartitionLocalMemory(winobj, sizeof(leadlag_context));
 		if(isnull)
+		{
+			if(context->last != NULL)
+			{
+				/* restore the stashed copy */
+				result = context->last;
+				isnull = context->last_isnull;
+			}
+		}
+		else
+		{
+			if(context->last != NULL)
+			{
+				/* 
+				 * This step is not strictly necessary as the Datum copies are
+				 * allocated in a context that'll be discarded after this query.
+				 * However, we'd like to avoid a large memory spike during the
+				 * query (as we'd get if we kept a copy of all the non-null 
+				 * results for the duration of the query) so we'll free the
+				 * Datum copies as we go along:
+				 */
+				WinFreeResultDatumCopy(winobj, context->last);
+			}
+			context->last = WinGetResultDatumCopy(winobj, result);
+			context->last_isnull = isnull;
+		}
+	}
+
+	if (isnull)
+	{
 		PG_RETURN_NULL();
+	}
 
 	PG_RETURN_DATUM(result);
 }
diff --git a/src/include/.DS_Store b/src/include/.DS_Store
new file mode 100644
index 0000000..d5711fe
Binary files /dev/null and b/src/include/.DS_Store differ
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2229ef0..a13c58b 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000 /* lead/lag/nth */
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..73524ca 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
@@ -61,4 +63,7 @@ extern Datum WinGetFuncArgInFrame(WindowObject winobj, int argno,
 extern Datum WinGetFuncArgCurrent(WindowObject winobj, int argno,
 					 bool *isnull);
 
+extern Datum WinGetResultDatumCopy(WindowObject winobj, Datum datum);
+extern void WinFreeResultDatumCopy(WindowObject winobj, Datum datum);
+
 #endif   /* WINDOWAPI_H */
diff --git a/src/interfaces/.DS_Store b/src/interfaces/.DS_Store
new file mode 100644
index 0000000..c8d03e0
Binary files /dev/null and b/src/interfaces/.DS_Store differ
diff --git a/src/interfaces/ecpg/.DS_Store b/src/interfaces/ecpg/.DS_Store
new file mode 100644
index 0000000..b3e3f35
Binary files /dev/null and b/src/interfaces/ecpg/.DS_Store differ
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index f4b51d6..fe5dcb3 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -45,6 +45,8 @@ my %replace_string = (
 	'WITH_TIME'    => 'with time',
 	'NULLS_FIRST'  => 'nulls first',
 	'NULLS_LAST'   => 'nulls last',
+	'RESPECT_NULLS'  => 'respect nulls',
+	'IGNORE_NULLS'   => 'ignore nulls',
 	'TYPECAST'     => '::',
 	'DOT_DOT'      => '..',
 	'COLON_EQUALS' => ':=',);
diff --git a/src/interfaces/ecpg/preproc/parser.c b/src/interfaces/ecpg/preproc/parser.c
index 2ce9dd9..53f4167 100644
--- a/src/interfaces/ecpg/preproc/parser.c
+++ b/src/interfaces/ecpg/preproc/parser.c
@@ -121,6 +121,53 @@ filtered_base_yylex(void)
 			}
 			break;
 
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
+					break;
+				default:
+					/* save the lookahead token for next time */
+					lookahead_token = next_token;
+					lookahead_yylval = base_yylval;
+					lookahead_yylloc = base_yylloc;
+					have_lookahead = true;
+					/* and back up the output info to cur_token */
+					base_yylval = cur_yylval;
+					base_yylloc = cur_yylloc;
+					break;
+			}
+			break;
+
 		default:
 			break;
 	}
diff --git a/src/test/.DS_Store b/src/test/.DS_Store
new file mode 100644
index 0000000..7c9864e
Binary files /dev/null and b/src/test/.DS_Store differ
diff --git a/src/test/regress/.DS_Store b/src/test/regress/.DS_Store
new file mode 100644
index 0000000..a623e62
Binary files /dev/null and b/src/test/regress/.DS_Store differ
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..41d76a6 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    favourite_animal text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,114 @@ 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
+-- test null behaviour: (1) lags
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+(10 rows)
+
+-- a numeric (date) column
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lag     
+------------
+ 
+ 
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT lag(favourite_animal) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+   lag   
+---------
+ 
+ frog
+ frog
+ frog
+ chicken
+ chicken
+ chicken
+ tiger
+ gorilla
+ gorilla
+(10 rows)
+
+-- (2) leads
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 
+ 
+ 11-17-2009
+ 
+ 
+ 
+ 
+(10 rows)
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+    lead    
+------------
+ 
+ 03-05-2009
+ 09-22-2010
+ 09-22-2010
+ 09-22-2010
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+ 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..67e9a9a 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    favourite_animal text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,25 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a numeric (date) column
+SELECT lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a text column
+SELECT lag(favourite_animal) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- (2) leads
+
+SELECT lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;

diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5094226..0309a99 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -488,6 +488,7 @@ 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
+				over_specification
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 
@@ -543,7 +544,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -573,7 +574,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -607,6 +608,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * creates these tokens when required.
  */
 %token			NULLS_FIRST NULLS_LAST WITH_TIME
+%token			RESPECT_NULLS IGNORE_NULLS
 
 
 /* Precedence: lowest to highest */
@@ -11752,7 +11754,8 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
+over_specification:
+			  OVER window_specification
 				{ $$ = $2; }
 			| OVER ColId
 				{
@@ -11767,6 +11770,18 @@ over_clause: OVER window_specification
 					n->location = @2;
 					$$ = n;
 				}
+			;
+
+over_clause: over_specification
+				{ $$ = $1; }
+			| RESPECT_NULLS over_specification
+				{ $$ = $2; }
+			| IGNORE_NULLS over_specification
+				{
+					if($2)
+						$2->frameOptions |= FRAMEOPTION_IGNORE_NULLS;
+					$$ = $2;
+				}	
 			| /*EMPTY*/
 				{ $$ = NULL; }
 		;
@@ -12740,6 +12755,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12827,6 +12843,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index b8ec790..1b2b2de 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -118,15 +118,7 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 					cur_token = NULLS_LAST;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					yyextra->lookahead_token = next_token;
-					yyextra->lookahead_yylval = lvalp->core_yystype;
-					yyextra->lookahead_yylloc = *llocp;
-					yyextra->have_lookahead = true;
-					/* and back up the output info to cur_token */
-					lvalp->core_yystype = cur_yylval;
-					*llocp = cur_yylloc;
-					break;
+					goto restore_next_token;
 			}
 			break;
 
@@ -144,15 +136,38 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 					cur_token = WITH_TIME;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					yyextra->lookahead_token = next_token;
-					yyextra->lookahead_yylval = lvalp->core_yystype;
-					yyextra->lookahead_yylloc = *llocp;
-					yyextra->have_lookahead = true;
-					/* and back up the output info to cur_token */
-					lvalp->core_yystype = cur_yylval;
-					*llocp = cur_yylloc;
+					goto restore_next_token;
+			}
+			break;
+
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					goto restore_next_token;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
 					break;
+				default:
+					goto restore_next_token;
 			}
 			break;
 
@@ -161,4 +176,16 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 	}
 
 	return cur_token;
+
+restore_next_token:
+	/* save the lookahead token for next time */
+	yyextra->lookahead_token = next_token;
+	yyextra->lookahead_yylval = lvalp->core_yystype;
+	yyextra->lookahead_yylloc = *llocp;
+	yyextra->have_lookahead = true;
+	/* and back up the output info to cur_token */
+	lvalp->core_yystype = cur_yylval;
+	*llocp = cur_yylloc;
+
+	return cur_token;
 }
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..84110ab 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -25,6 +25,15 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * structure for IGNORE NULLS / RESPECT NULLS semantics
+ */
+typedef struct leadlag_context
+{
+	int64		last;			/* last non-null result, initially 0 */
+	bool		seen_one;		/* true iff we can output the row in "last" now */
+} leadlag_context;
+
+/*
  * ntile process information
  */
 typedef struct
@@ -292,6 +301,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
+	leadlag_context* context;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but we can't move the mark
+	 * beyond the last non-null tuple!
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,11 +323,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
 
 	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
+									  offset,
 									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+									  const_offset && !ignore_nulls,
 									  &isnull, &isout);
 
 	if (isout)
@@ -322,6 +344,34 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	if (ignore_nulls)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us. 
+		 */
+		context = (leadlag_context *) 
+			WinGetPartitionLocalMemory(winobj, sizeof(leadlag_context));
+ 		if (isnull)
+		{
+			if (context->seen_one)
+			{
+				/* restore the datum at the stashed index */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  context->last,
+									  WINDOW_SEEK_HEAD,
+									  const_offset,  /* drag mark up after us */
+									  &isnull, &isout);
+			}
+		}
+		else
+		{
+			/* work out which tuple we just loaded */
+			context->last = WinGetCurrentPosition(winobj) + offset;
+			context->seen_one = true;
+		}
+	}
+
 	if (isnull)
 		PG_RETURN_NULL();
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..59fc635 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000 /* lead/lag/nth */
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index f4b51d6..fe5dcb3 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -45,6 +45,8 @@ my %replace_string = (
 	'WITH_TIME'    => 'with time',
 	'NULLS_FIRST'  => 'nulls first',
 	'NULLS_LAST'   => 'nulls last',
+	'RESPECT_NULLS'  => 'respect nulls',
+	'IGNORE_NULLS'   => 'ignore nulls',
 	'TYPECAST'     => '::',
 	'DOT_DOT'      => '..',
 	'COLON_EQUALS' => ':=',);
diff --git a/src/interfaces/ecpg/preproc/parser.c b/src/interfaces/ecpg/preproc/parser.c
index 2ce9dd9..3780652 100644
--- a/src/interfaces/ecpg/preproc/parser.c
+++ b/src/interfaces/ecpg/preproc/parser.c
@@ -83,15 +83,7 @@ filtered_base_yylex(void)
 					cur_token = NULLS_LAST;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
-					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
-					break;
+					goto restore_next_token;
 			}
 			break;
 
@@ -109,15 +101,38 @@ filtered_base_yylex(void)
 					cur_token = WITH_TIME;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
-					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
+					goto restore_next_token;
+			}
+			break;
+
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					goto restore_next_token;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
 					break;
+				default:
+					goto restore_next_token;
 			}
 			break;
 
@@ -126,4 +141,16 @@ filtered_base_yylex(void)
 	}
 
 	return cur_token;
+
+restore_next_token:
+	/* save the lookahead token for next time */
+	lookahead_token = next_token;
+	lookahead_yylval = base_yylval;
+	lookahead_yylloc = base_yylloc;
+	have_lookahead = true;
+	/* and back up the output info to cur_token */
+	base_yylval = cur_yylval;
+	base_yylloc = cur_yylloc;
+
+	return cur_token;
 }
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..47e3ba2 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,114 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 09-22-2010
+            | 09-22-2010
+            | 11-17-2009
+ 11-17-2009 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..eb0817b 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,25 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5094226..aae35d8 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -401,7 +402,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <node>	columnDef columnOptions
 %type <defelt>	def_elem reloption_elem old_aggr_elem
 %type <node>	def_arg columnElem where_clause where_or_current_clause
-				a_expr b_expr c_expr func_expr AexprConst indirection_el
+				a_expr b_expr c_expr AexprConst indirection_el
 				columnref in_expr having_clause func_table array_expr
 				ExclusionWhereClause
 %type <list>	ExclusionConstraintList ExclusionConstraintElem
@@ -481,6 +482,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	document_or_content
 %type <boolean> xml_whitespace_option
 
+%type <node>	func_application func_expr_common_subexpr
+%type <node>	func_expr func_expr_windowless
 %type <node>	common_table_expr
 %type <with>	with_clause opt_with_clause
 %type <list>	cte_list
@@ -543,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -573,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -6132,7 +6135,7 @@ index_elem:	ColId opt_collate opt_class opt_asc_desc opt_nulls_order
 					$$->ordering = $4;
 					$$->nulls_ordering = $5;
 				}
-			| func_expr opt_collate opt_class opt_asc_desc opt_nulls_order
+			| func_expr_windowless opt_collate opt_class opt_asc_desc opt_nulls_order
 				{
 					$$ = makeNode(IndexElem);
 					$$->name = NULL;
@@ -9894,11 +9897,9 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
-
-func_table: func_expr								{ $$ = $1; }
+func_table: func_expr_windowless					{ $$ = $1; }
 		;
 
-
 where_clause:
 			WHERE a_expr							{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NULL; }
@@ -11079,15 +11080,7 @@ c_expr:		columnref								{ $$ = $1; }
 				}
 		;
 
-/*
- * func_expr is split out from c_expr just so that we have a classification
- * for "everything that is a function call or looks like one".  This isn't
- * very important, but it saves us having to document which variants are
- * legal in the backwards-compatible functional-index syntax for CREATE INDEX.
- * (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_name '(' ')' over_clause
+func_application: func_name '(' ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11096,11 +11089,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $4;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ')' over_clause
+			| func_name '(' func_arg_list ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11109,11 +11102,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11122,11 +11115,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11135,11 +11128,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $8;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list sort_clause ')' over_clause
+			| func_name '(' func_arg_list sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11148,11 +11141,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' ALL func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' ALL func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11165,11 +11158,11 @@ func_expr:	func_name '(' ')' over_clause
 					 * for that in FuncCall at the moment.
 					 */
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11178,11 +11171,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = TRUE;
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' '*' ')' over_clause
+			| func_name '(' '*' ')'
 				{
 					/*
 					 * We consider AGGREGATE(*) to invoke a parameterless
@@ -11201,11 +11194,48 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = TRUE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| COLLATION FOR '(' a_expr ')'
+        ;
+
+
+/*
+ * func_expr and its cousin func_expr_windowless is split out from c_expr just 
+ * so that we have classifications for "everything that is a function call or 
+ * looks like one".  This isn't very important, but it saves us having to document 
+ * which variants are legal in the backwards-compatible functional-index syntax 
+ * for CREATE INDEX.
+ * (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 over_clause 
+				{
+              		FuncCall *n = (FuncCall*)$1;
+					n->over = $2;
+					$$ = (Node*)n;
+				} 
+			| func_expr_common_subexpr
+				{ $$ = $1; }
+		;
+
+/* 
+ * As func_expr but does not accept WINDOW functions directly (they
+ * can still be contained in arguments for functions etc.)
+ * Use this when window expressions are not allowed, so to decomplicate
+ * the grammar. (e.g. in CREATE INDEX)
+ */
+func_expr_windowless: 
+			func_application						{ $$ = $1; }
+			| func_expr_common_subexpr 				{ $$ = $1; }
+		;
+
+/*
+ * Special expression 
+ */
+func_expr_common_subexpr:	
+			COLLATION FOR '(' a_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = SystemFuncName("pg_collation_for");
@@ -11752,16 +11782,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12740,6 +12779,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12827,6 +12867,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/window.out b/src/test/regress/expected/window.out
index 752c7b4..cb34a7c 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -989,9 +989,9 @@ ERROR:  window functions are not allowed in GROUP BY
 LINE 1: SELECT rank() OVER (ORDER BY 1), count(*) FROM empsalary GRO...
                ^
 SELECT * FROM rank() OVER (ORDER BY random());
-ERROR:  window functions are not allowed in functions in FROM
+ERROR:  syntax error at or near "OVER"
 LINE 1: SELECT * FROM rank() OVER (ORDER BY random());
-                      ^
+                             ^
 DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())) > 10;
 ERROR:  window functions are not allowed in WHERE
 LINE 1: DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())...

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 4c5af4b..89d28b2 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12266,6 +12266,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12280,7 +12281,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12293,6 +12297,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12307,7 +12312,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12401,11 +12408,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5094226..0309a99 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -488,6 +488,7 @@ 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
+				over_specification
 %type <str>		opt_existing_window_name
 %type <boolean> opt_if_not_exists
 
@@ -543,7 +544,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -573,7 +574,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -607,6 +608,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  * creates these tokens when required.
  */
 %token			NULLS_FIRST NULLS_LAST WITH_TIME
+%token			RESPECT_NULLS IGNORE_NULLS
 
 
 /* Precedence: lowest to highest */
@@ -11752,7 +11754,8 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
+over_specification:
+			  OVER window_specification
 				{ $$ = $2; }
 			| OVER ColId
 				{
@@ -11767,6 +11770,18 @@ over_clause: OVER window_specification
 					n->location = @2;
 					$$ = n;
 				}
+			;
+
+over_clause: over_specification
+				{ $$ = $1; }
+			| RESPECT_NULLS over_specification
+				{ $$ = $2; }
+			| IGNORE_NULLS over_specification
+				{
+					if($2)
+						$2->frameOptions |= FRAMEOPTION_IGNORE_NULLS;
+					$$ = $2;
+				}	
 			| /*EMPTY*/
 				{ $$ = NULL; }
 		;
@@ -12740,6 +12755,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12827,6 +12843,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parser.c b/src/backend/parser/parser.c
index b8ec790..1b2b2de 100644
--- a/src/backend/parser/parser.c
+++ b/src/backend/parser/parser.c
@@ -118,15 +118,7 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 					cur_token = NULLS_LAST;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					yyextra->lookahead_token = next_token;
-					yyextra->lookahead_yylval = lvalp->core_yystype;
-					yyextra->lookahead_yylloc = *llocp;
-					yyextra->have_lookahead = true;
-					/* and back up the output info to cur_token */
-					lvalp->core_yystype = cur_yylval;
-					*llocp = cur_yylloc;
-					break;
+					goto restore_next_token;
 			}
 			break;
 
@@ -144,15 +136,38 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 					cur_token = WITH_TIME;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					yyextra->lookahead_token = next_token;
-					yyextra->lookahead_yylval = lvalp->core_yystype;
-					yyextra->lookahead_yylloc = *llocp;
-					yyextra->have_lookahead = true;
-					/* and back up the output info to cur_token */
-					lvalp->core_yystype = cur_yylval;
-					*llocp = cur_yylloc;
+					goto restore_next_token;
+			}
+			break;
+
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					goto restore_next_token;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = lvalp->core_yystype;
+			cur_yylloc = *llocp;
+			next_token = core_yylex(&(lvalp->core_yystype), llocp, yyscanner);
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
 					break;
+				default:
+					goto restore_next_token;
 			}
 			break;
 
@@ -161,4 +176,16 @@ base_yylex(YYSTYPE *lvalp, YYLTYPE *llocp, core_yyscan_t yyscanner)
 	}
 
 	return cur_token;
+
+restore_next_token:
+	/* save the lookahead token for next time */
+	yyextra->lookahead_token = next_token;
+	yyextra->lookahead_yylval = lvalp->core_yystype;
+	yyextra->lookahead_yylloc = *llocp;
+	yyextra->have_lookahead = true;
+	/* and back up the output info to cur_token */
+	lvalp->core_yystype = cur_yylval;
+	*llocp = cur_yylloc;
+
+	return cur_token;
 }
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..8985149 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -25,6 +25,15 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * structure for IGNORE NULLS / RESPECT NULLS semantics
+ */
+typedef struct leadlag_context
+{
+	int64		last;			/* last non-null result, initially 0 */
+	bool		seen_one;		/* true iff we can output the row in "last" now */
+} leadlag_context;
+
+/*
  * ntile process information
  */
 typedef struct
@@ -292,6 +301,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
+	leadlag_context* context;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but we can't move the mark
+	 * beyond the last non-null tuple!
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,11 +323,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
 
 	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
+									  offset,
 									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+									  const_offset && !ignore_nulls,
 									  &isnull, &isout);
 
 	if (isout)
@@ -322,6 +344,39 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	/*
+	 * If the row's out of the partition we don't want to propagate the 
+	 * last non-null value if we're RESPECTing NULLS - we'll just leave
+	 * the default value (if there was one).
+	 */
+	if (ignore_nulls && !isout)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us. 
+		 */
+		context = (leadlag_context *) 
+			WinGetPartitionLocalMemory(winobj, sizeof(leadlag_context));
+ 		if (isnull)
+		{
+			if (context->seen_one)
+			{
+				/* restore the datum at the stashed index */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  context->last,
+									  WINDOW_SEEK_HEAD,
+									  const_offset,  /* drag mark up after us */
+									  &isnull, &isout);
+			}
+		}
+		else
+		{
+			/* work out which tuple we just loaded */
+			context->last = WinGetCurrentPosition(winobj) + offset;
+			context->seen_one = true;
+		}
+	}
+
 	if (isnull)
 		PG_RETURN_NULL();
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..59fc635 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000 /* lead/lag/nth */
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/interfaces/ecpg/preproc/parse.pl b/src/interfaces/ecpg/preproc/parse.pl
index f4b51d6..fe5dcb3 100644
--- a/src/interfaces/ecpg/preproc/parse.pl
+++ b/src/interfaces/ecpg/preproc/parse.pl
@@ -45,6 +45,8 @@ my %replace_string = (
 	'WITH_TIME'    => 'with time',
 	'NULLS_FIRST'  => 'nulls first',
 	'NULLS_LAST'   => 'nulls last',
+	'RESPECT_NULLS'  => 'respect nulls',
+	'IGNORE_NULLS'   => 'ignore nulls',
 	'TYPECAST'     => '::',
 	'DOT_DOT'      => '..',
 	'COLON_EQUALS' => ':=',);
diff --git a/src/interfaces/ecpg/preproc/parser.c b/src/interfaces/ecpg/preproc/parser.c
index 2ce9dd9..3780652 100644
--- a/src/interfaces/ecpg/preproc/parser.c
+++ b/src/interfaces/ecpg/preproc/parser.c
@@ -83,15 +83,7 @@ filtered_base_yylex(void)
 					cur_token = NULLS_LAST;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
-					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
-					break;
+					goto restore_next_token;
 			}
 			break;
 
@@ -109,15 +101,38 @@ filtered_base_yylex(void)
 					cur_token = WITH_TIME;
 					break;
 				default:
-					/* save the lookahead token for next time */
-					lookahead_token = next_token;
-					lookahead_yylval = base_yylval;
-					lookahead_yylloc = base_yylloc;
-					have_lookahead = true;
-					/* and back up the output info to cur_token */
-					base_yylval = cur_yylval;
-					base_yylloc = cur_yylloc;
+					goto restore_next_token;
+			}
+			break;
+
+		/*
+		 * Window functions can use RESPECT NULLS or IGNORE NULLS to
+		 * modify their behaviour
+		 */
+		case RESPECT:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = RESPECT_NULLS;
+					break;
+				default:
+					goto restore_next_token;
+			}
+			break;
+		case IGNORE:
+			cur_yylval = base_yylval;
+			cur_yylloc = base_yylloc;
+			next_token = base_yylex();
+			switch (next_token)
+			{
+				case NULLS_P:
+					cur_token = IGNORE_NULLS;
 					break;
+				default:
+					goto restore_next_token;
 			}
 			break;
 
@@ -126,4 +141,16 @@ filtered_base_yylex(void)
 	}
 
 	return cur_token;
+
+restore_next_token:
+	/* save the lookahead token for next time */
+	lookahead_token = next_token;
+	lookahead_yylval = base_yylval;
+	lookahead_yylloc = base_yylloc;
+	have_lookahead = true;
+	/* and back up the output info to cur_token */
+	base_yylval = cur_yylval;
+	base_yylloc = cur_yylloc;
+
+	return cur_token;
 }
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..9a80158 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,135 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 09-22-2010
+            | 09-22-2010
+            | 11-17-2009
+ 11-17-2009 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+            | 
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    4
+   4 |    4
+     |    4
+     |    5
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..6dba56e 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,35 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table;
+
+DROP TABLE test_table;

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 4c5af4b..89d28b2 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12266,6 +12266,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12280,7 +12281,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12293,6 +12297,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12307,7 +12312,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12401,11 +12408,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5094226..aae35d8 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -401,7 +402,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <node>	columnDef columnOptions
 %type <defelt>	def_elem reloption_elem old_aggr_elem
 %type <node>	def_arg columnElem where_clause where_or_current_clause
-				a_expr b_expr c_expr func_expr AexprConst indirection_el
+				a_expr b_expr c_expr AexprConst indirection_el
 				columnref in_expr having_clause func_table array_expr
 				ExclusionWhereClause
 %type <list>	ExclusionConstraintList ExclusionConstraintElem
@@ -481,6 +482,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	document_or_content
 %type <boolean> xml_whitespace_option
 
+%type <node>	func_application func_expr_common_subexpr
+%type <node>	func_expr func_expr_windowless
 %type <node>	common_table_expr
 %type <with>	with_clause opt_with_clause
 %type <list>	cte_list
@@ -543,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -573,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -6132,7 +6135,7 @@ index_elem:	ColId opt_collate opt_class opt_asc_desc opt_nulls_order
 					$$->ordering = $4;
 					$$->nulls_ordering = $5;
 				}
-			| func_expr opt_collate opt_class opt_asc_desc opt_nulls_order
+			| func_expr_windowless opt_collate opt_class opt_asc_desc opt_nulls_order
 				{
 					$$ = makeNode(IndexElem);
 					$$->name = NULL;
@@ -9894,11 +9897,9 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
-
-func_table: func_expr								{ $$ = $1; }
+func_table: func_expr_windowless					{ $$ = $1; }
 		;
 
-
 where_clause:
 			WHERE a_expr							{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NULL; }
@@ -11079,15 +11080,7 @@ c_expr:		columnref								{ $$ = $1; }
 				}
 		;
 
-/*
- * func_expr is split out from c_expr just so that we have a classification
- * for "everything that is a function call or looks like one".  This isn't
- * very important, but it saves us having to document which variants are
- * legal in the backwards-compatible functional-index syntax for CREATE INDEX.
- * (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_name '(' ')' over_clause
+func_application: func_name '(' ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11096,11 +11089,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $4;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ')' over_clause
+			| func_name '(' func_arg_list ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11109,11 +11102,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11122,11 +11115,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11135,11 +11128,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $8;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list sort_clause ')' over_clause
+			| func_name '(' func_arg_list sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11148,11 +11141,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' ALL func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' ALL func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11165,11 +11158,11 @@ func_expr:	func_name '(' ')' over_clause
 					 * for that in FuncCall at the moment.
 					 */
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11178,11 +11171,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = TRUE;
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' '*' ')' over_clause
+			| func_name '(' '*' ')'
 				{
 					/*
 					 * We consider AGGREGATE(*) to invoke a parameterless
@@ -11201,11 +11194,48 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = TRUE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| COLLATION FOR '(' a_expr ')'
+        ;
+
+
+/*
+ * func_expr and its cousin func_expr_windowless is split out from c_expr just 
+ * so that we have classifications for "everything that is a function call or 
+ * looks like one".  This isn't very important, but it saves us having to document 
+ * which variants are legal in the backwards-compatible functional-index syntax 
+ * for CREATE INDEX.
+ * (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 over_clause 
+				{
+              		FuncCall *n = (FuncCall*)$1;
+					n->over = $2;
+					$$ = (Node*)n;
+				} 
+			| func_expr_common_subexpr
+				{ $$ = $1; }
+		;
+
+/* 
+ * As func_expr but does not accept WINDOW functions directly (they
+ * can still be contained in arguments for functions etc.)
+ * Use this when window expressions are not allowed, so to decomplicate
+ * the grammar. (e.g. in CREATE INDEX)
+ */
+func_expr_windowless: 
+			func_application						{ $$ = $1; }
+			| func_expr_common_subexpr 				{ $$ = $1; }
+		;
+
+/*
+ * Special expression 
+ */
+func_expr_common_subexpr:	
+			COLLATION FOR '(' a_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = SystemFuncName("pg_collation_for");
@@ -11752,16 +11782,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12740,6 +12779,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12827,6 +12867,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..8985149 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -25,6 +25,15 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * structure for IGNORE NULLS / RESPECT NULLS semantics
+ */
+typedef struct leadlag_context
+{
+	int64		last;			/* last non-null result, initially 0 */
+	bool		seen_one;		/* true iff we can output the row in "last" now */
+} leadlag_context;
+
+/*
  * ntile process information
  */
 typedef struct
@@ -292,6 +301,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 	Datum		result;
 	bool		isnull;
 	bool		isout;
+	bool		ignore_nulls;
+	leadlag_context* context;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but we can't move the mark
+	 * beyond the last non-null tuple!
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,11 +323,15 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
 
 	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
+									  offset,
 									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+									  const_offset && !ignore_nulls,
 									  &isnull, &isout);
 
 	if (isout)
@@ -322,6 +344,39 @@ leadlag_common(FunctionCallInfo fcinfo,
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
 	}
 
+	/*
+	 * If the row's out of the partition we don't want to propagate the 
+	 * last non-null value if we're RESPECTing NULLS - we'll just leave
+	 * the default value (if there was one).
+	 */
+	if (ignore_nulls && !isout)
+	{
+		/*
+		 * We'll keep the last non-null value we've seen in our per-partition chunk
+		 * of memory, so it gets cleaned up for us. 
+		 */
+		context = (leadlag_context *) 
+			WinGetPartitionLocalMemory(winobj, sizeof(leadlag_context));
+ 		if (isnull)
+		{
+			if (context->seen_one)
+			{
+				/* restore the datum at the stashed index */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  context->last,
+									  WINDOW_SEEK_HEAD,
+									  const_offset,  /* drag mark up after us */
+									  &isnull, &isout);
+			}
+		}
+		else
+		{
+			/* work out which tuple we just loaded */
+			context->last = WinGetCurrentPosition(winobj) + offset;
+			context->seen_one = true;
+		}
+	}
+
 	if (isnull)
 		PG_RETURN_NULL();
 
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..c6f72f8 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -989,9 +991,9 @@ ERROR:  window functions are not allowed in GROUP BY
 LINE 1: SELECT rank() OVER (ORDER BY 1), count(*) FROM empsalary GRO...
                ^
 SELECT * FROM rank() OVER (ORDER BY random());
-ERROR:  window functions are not allowed in functions in FROM
+ERROR:  syntax error at or near "OVER"
 LINE 1: SELECT * FROM rank() OVER (ORDER BY random());
-                      ^
+                             ^
 DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())) > 10;
 ERROR:  window functions are not allowed in WHERE
 LINE 1: DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())...
@@ -1020,5 +1022,135 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 09-22-2010
+            | 09-22-2010
+            | 11-17-2009
+ 11-17-2009 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+            | 
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    4
+   4 |    4
+     |    4
+     |    5
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..6dba56e 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,35 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table;
+
+DROP TABLE test_table;

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 4c5af4b..89d28b2 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12266,6 +12266,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12280,7 +12281,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12293,6 +12297,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12307,7 +12312,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <literal>IGNORE NULLS</> is specified and a previous evalution in the
+       current window has returned a non-null value then that value will be
+       returned instead.
       </entry>
      </row>
 
@@ -12401,11 +12408,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..70e84d1 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -26,9 +26,6 @@
 #define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
 #define BITNUM(x)	((x) % BITS_PER_BITMAPWORD)
 
-#define BITMAPSET_SIZE(nwords)	\
-	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
-
 /*----------
  * This is a well-known cute trick for isolating the rightmost one-bit
  * in a word.  It assumes two's complement arithmetic.  Consider any
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 5094226..aae35d8 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -401,7 +402,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <node>	columnDef columnOptions
 %type <defelt>	def_elem reloption_elem old_aggr_elem
 %type <node>	def_arg columnElem where_clause where_or_current_clause
-				a_expr b_expr c_expr func_expr AexprConst indirection_el
+				a_expr b_expr c_expr AexprConst indirection_el
 				columnref in_expr having_clause func_table array_expr
 				ExclusionWhereClause
 %type <list>	ExclusionConstraintList ExclusionConstraintElem
@@ -481,6 +482,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	document_or_content
 %type <boolean> xml_whitespace_option
 
+%type <node>	func_application func_expr_common_subexpr
+%type <node>	func_expr func_expr_windowless
 %type <node>	common_table_expr
 %type <with>	with_clause opt_with_clause
 %type <list>	cte_list
@@ -543,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -573,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -6132,7 +6135,7 @@ index_elem:	ColId opt_collate opt_class opt_asc_desc opt_nulls_order
 					$$->ordering = $4;
 					$$->nulls_ordering = $5;
 				}
-			| func_expr opt_collate opt_class opt_asc_desc opt_nulls_order
+			| func_expr_windowless opt_collate opt_class opt_asc_desc opt_nulls_order
 				{
 					$$ = makeNode(IndexElem);
 					$$->name = NULL;
@@ -9894,11 +9897,9 @@ relation_expr_opt_alias: relation_expr					%prec UMINUS
 				}
 		;
 
-
-func_table: func_expr								{ $$ = $1; }
+func_table: func_expr_windowless					{ $$ = $1; }
 		;
 
-
 where_clause:
 			WHERE a_expr							{ $$ = $2; }
 			| /*EMPTY*/								{ $$ = NULL; }
@@ -11079,15 +11080,7 @@ c_expr:		columnref								{ $$ = $1; }
 				}
 		;
 
-/*
- * func_expr is split out from c_expr just so that we have a classification
- * for "everything that is a function call or looks like one".  This isn't
- * very important, but it saves us having to document which variants are
- * legal in the backwards-compatible functional-index syntax for CREATE INDEX.
- * (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_name '(' ')' over_clause
+func_application: func_name '(' ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11096,11 +11089,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $4;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ')' over_clause
+			| func_name '(' func_arg_list ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11109,11 +11102,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11122,11 +11115,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')' over_clause
+			| func_name '(' func_arg_list ',' VARIADIC func_arg_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11135,11 +11128,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = TRUE;
-					n->over = $8;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' func_arg_list sort_clause ')' over_clause
+			| func_name '(' func_arg_list sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11148,11 +11141,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $6;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' ALL func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' ALL func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11165,11 +11158,11 @@ func_expr:	func_name '(' ')' over_clause
 					 * for that in FuncCall at the moment.
 					 */
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')' over_clause
+			| func_name '(' DISTINCT func_arg_list opt_sort_clause ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = $1;
@@ -11178,11 +11171,11 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = FALSE;
 					n->agg_distinct = TRUE;
 					n->func_variadic = FALSE;
-					n->over = $7;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| func_name '(' '*' ')' over_clause
+			| func_name '(' '*' ')'
 				{
 					/*
 					 * We consider AGGREGATE(*) to invoke a parameterless
@@ -11201,11 +11194,48 @@ func_expr:	func_name '(' ')' over_clause
 					n->agg_star = TRUE;
 					n->agg_distinct = FALSE;
 					n->func_variadic = FALSE;
-					n->over = $5;
+					n->over = NULL;
 					n->location = @1;
 					$$ = (Node *)n;
 				}
-			| COLLATION FOR '(' a_expr ')'
+        ;
+
+
+/*
+ * func_expr and its cousin func_expr_windowless is split out from c_expr just 
+ * so that we have classifications for "everything that is a function call or 
+ * looks like one".  This isn't very important, but it saves us having to document 
+ * which variants are legal in the backwards-compatible functional-index syntax 
+ * for CREATE INDEX.
+ * (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 over_clause 
+				{
+              		FuncCall *n = (FuncCall*)$1;
+					n->over = $2;
+					$$ = (Node*)n;
+				} 
+			| func_expr_common_subexpr
+				{ $$ = $1; }
+		;
+
+/* 
+ * As func_expr but does not accept WINDOW functions directly (they
+ * can still be contained in arguments for functions etc.)
+ * Use this when window expressions are not allowed, so to decomplicate
+ * the grammar. (e.g. in CREATE INDEX)
+ */
+func_expr_windowless: 
+			func_application						{ $$ = $1; }
+			| func_expr_common_subexpr 				{ $$ = $1; }
+		;
+
+/*
+ * Special expression 
+ */
+func_expr_common_subexpr:	
+			COLLATION FOR '(' a_expr ')'
 				{
 					FuncCall *n = makeNode(FuncCall);
 					n->funcname = SystemFuncName("pg_collation_for");
@@ -11752,16 +11782,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12740,6 +12779,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12827,6 +12867,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..b14491c 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,13 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+ #define SET_WITHOUT_RESIZING(b, i) b->words[(i) / BITS_PER_BITMAPWORD] |= (bitmapword) 1 << (i) % BITS_PER_BITMAPWORD
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +288,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +299,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +324,134 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, words_needed, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+		words_needed = (bits_needed / BITS_PER_BITMAPWORD) + 1;
+
+		null_values = (Bitmapset *) WinGetPartitionLocalMemory(
+			winobj,
+			BITMAPSET_SIZE(words_needed));
+		Assert(null_values);
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* update our bitmap with this result */
+				SET_WITHOUT_RESIZING(null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{					
+					SET_WITHOUT_RESIZING(null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * A | lag(A, 1)
+				 * 1 | 
+				 * 2 |  1
+				 *   |  ?
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..710000f 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -34,7 +34,8 @@ typedef struct Bitmapset
 	int			nwords;			/* number of words in array */
 	bitmapword	words[1];		/* really [nwords] */
 } Bitmapset;					/* VARIABLE LENGTH STRUCT */
-
+#define BITMAPSET_SIZE(nwords)	\
+	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
 
 /* result of bms_subset_compare */
 typedef enum
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 68a13b7..2acf073 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 752c7b4..f136a56 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -989,9 +991,9 @@ ERROR:  window functions are not allowed in GROUP BY
 LINE 1: SELECT rank() OVER (ORDER BY 1), count(*) FROM empsalary GRO...
                ^
 SELECT * FROM rank() OVER (ORDER BY random());
-ERROR:  window functions are not allowed in functions in FROM
+ERROR:  syntax error at or near "OVER"
 LINE 1: SELECT * FROM rank() OVER (ORDER BY random());
-                      ^
+                             ^
 DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())) > 10;
 ERROR:  window functions are not allowed in WHERE
 LINE 1: DELETE FROM empsalary WHERE (rank() OVER (ORDER BY random())...
@@ -1020,5 +1022,135 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..92166d7 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,35 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+
+DROP TABLE test_table;

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..9f96fe3 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [respect nulls]|[ignore nulls]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,8 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12415,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..70e84d1 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -26,9 +26,6 @@
 #define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
 #define BITNUM(x)	((x) % BITS_PER_BITMAPWORD)
 
-#define BITMAPSET_SIZE(nwords)	\
-	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
-
 /*----------
  * This is a well-known cute trick for isolating the rightmost one-bit
  * in a word.  It assumes two's complement arithmetic.  Consider any
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..b14491c 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,13 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+ #define SET_WITHOUT_RESIZING(b, i) b->words[(i) / BITS_PER_BITMAPWORD] |= (bitmapword) 1 << (i) % BITS_PER_BITMAPWORD
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +288,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +299,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +324,134 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, words_needed, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+		words_needed = (bits_needed / BITS_PER_BITMAPWORD) + 1;
+
+		null_values = (Bitmapset *) WinGetPartitionLocalMemory(
+			winobj,
+			BITMAPSET_SIZE(words_needed));
+		Assert(null_values);
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* update our bitmap with this result */
+				SET_WITHOUT_RESIZING(null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{					
+					SET_WITHOUT_RESIZING(null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * A | lag(A, 1)
+				 * 1 | 
+				 * 2 |  1
+				 *   |  ?
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..710000f 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -34,7 +34,8 @@ typedef struct Bitmapset
 	int			nwords;			/* number of words in array */
 	bitmapword	words[1];		/* really [nwords] */
 } Bitmapset;					/* VARIABLE LENGTH STRUCT */
-
+#define BITMAPSET_SIZE(nwords)	\
+	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
 
 /* result of bms_subset_compare */
 typedef enum
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..473c7f3 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,135 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..92166d7 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,35 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+
+DROP TABLE test_table;

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..740e713 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12416,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..70e84d1 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -26,9 +26,6 @@
 #define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
 #define BITNUM(x)	((x) % BITS_PER_BITMAPWORD)
 
-#define BITMAPSET_SIZE(nwords)	\
-	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
-
 /*----------
  * This is a well-known cute trick for isolating the rightmost one-bit
  * in a word.  It assumes two's complement arithmetic.  Consider any
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..12cab3c 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,13 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+ #define SET_WITHOUT_RESIZING(b, i) b->words[(i) / BITS_PER_BITMAPWORD] |= (bitmapword) 1 << (i) % BITS_PER_BITMAPWORD
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +288,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +299,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +324,136 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, words_needed, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+		words_needed = (bits_needed / BITS_PER_BITMAPWORD) + 1;
+
+		null_values = (Bitmapset *) WinGetPartitionLocalMemory(
+			winobj,
+			BITMAPSET_SIZE(words_needed));
+		null_values->nwords = (int) words_needed;
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* update our bitmap with this result */
+				SET_WITHOUT_RESIZING(null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{					
+					SET_WITHOUT_RESIZING(null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..710000f 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -34,7 +34,8 @@ typedef struct Bitmapset
 	int			nwords;			/* number of words in array */
 	bitmapword	words[1];		/* really [nwords] */
 } Bitmapset;					/* VARIABLE LENGTH STRUCT */
-
+#define BITMAPSET_SIZE(nwords)	\
+	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
 
 /* result of bms_subset_compare */
 typedef enum
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..473c7f3 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,135 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..92166d7 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,35 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+
+DROP TABLE test_table;

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..740e713 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12416,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..70e84d1 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -26,9 +26,6 @@
 #define WORDNUM(x)	((x) / BITS_PER_BITMAPWORD)
 #define BITNUM(x)	((x) % BITS_PER_BITMAPWORD)
 
-#define BITMAPSET_SIZE(nwords)	\
-	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
-
 /*----------
  * This is a well-known cute trick for isolating the rightmost one-bit
  * in a word.  It assumes two's complement arithmetic.  Consider any
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index ae7d195..1eeeb97 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -482,6 +482,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..12cab3c 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,13 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+ #define SET_WITHOUT_RESIZING(b, i) b->words[(i) / BITS_PER_BITMAPWORD] |= (bitmapword) 1 << (i) % BITS_PER_BITMAPWORD
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +288,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +299,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +324,136 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, words_needed, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+		words_needed = (bits_needed / BITS_PER_BITMAPWORD) + 1;
+
+		null_values = (Bitmapset *) WinGetPartitionLocalMemory(
+			winobj,
+			BITMAPSET_SIZE(words_needed));
+		null_values->nwords = (int) words_needed;
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* update our bitmap with this result */
+				SET_WITHOUT_RESIZING(null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{					
+					SET_WITHOUT_RESIZING(null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..710000f 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -34,7 +34,8 @@ typedef struct Bitmapset
 	int			nwords;			/* number of words in array */
 	bitmapword	words[1];		/* really [nwords] */
 } Bitmapset;					/* VARIABLE LENGTH STRUCT */
-
+#define BITMAPSET_SIZE(nwords)	\
+	(offsetof(Bitmapset, words) + (nwords) * sizeof(bitmapword))
 
 /* result of bms_subset_compare */
 typedef enum
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..3e67cc0 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,151 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w,
+	lead(val, 2) RESPECT NULLS OVER w
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..6018502 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,47 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w,
+	lead(val, 2) RESPECT NULLS OVER w
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..740e713 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12416,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..e1a1020 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2000,6 +2000,16 @@ WinGetCurrentPosition(WindowObject winobj)
 	Assert(WindowObjectIsValid(winobj));
 	return winobj->winstate->currentpos;
 }
+/*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
 
 /*
  * WinGetPartitionRowCount
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..1650382 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -866,3 +866,35 @@ bms_hash_value(const Bitmapset *a)
 	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
 								   (lastword + 1) * sizeof(bitmapword)));
 }
+
+
+/* 
+ * bms_initialize - initialize a Bitmapset using a custom memory allocator
+ *
+ * allocator
+ *		A function pointer that will be called once to initialize the
+ *		required amount of (zeroed-out) memory
+ * allocator_arg
+ *		An argument that will be passed unmodified to the allocator 
+ * 		function. Use this to pass any state the allocator requires.
+ * nbits
+ * 		The maximum capacity of the Bitmapset. An int64 as a Bitmapset with
+ * 		INT_MAX words can store more than INT_MAX bits.
+ */
+Bitmapset *
+bms_initialize(
+	void *(*allocator) (void *arg, Size sz),
+	void *allocator_arg,
+	int64 nbits)
+{
+	int nwords;
+	Bitmapset * b;
+
+	nwords = (nbits / BITS_PER_BITMAPWORD) + 1;
+	b = (Bitmapset *) allocator(allocator_arg, BITMAPSET_SIZE(nwords));
+
+	/* set up the Bitmapset's state */
+	b->nwords = nwords;
+
+	return b;
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 7380618..7d8890a 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -572,8 +572,7 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
@@ -582,7 +581,38 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 			winref++;
 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
 			{
-				wfunc->winref = winref;
+				/*
+				 * This is the window we want - but we may have to tweak the
+				 * definition slightly (e.g. to support the IGNORE NULLS
+				 * frame option). If so, clone it (but reset the name so 
+				 * subsequent calls continue to use the original definition)
+				 */
+				if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+					wfunc->winref = winref;
+				else
+				{
+					WindowDef *clone;
+					char *name;
+
+					/*
+					 * We want to avoid cloning the window name when we copy
+					 * the object as we're not going to use it.
+					 */
+					name = refwin->name;
+					refwin->name = NULL;
+					clone = (WindowDef *) copyObject(refwin);
+					refwin->name = name;
+
+					/* Override the clone's fields with the ones we want */
+					clone->frameOptions = windef->frameOptions;
+
+					/*
+					 * Add this new definition to the list. Note that there's
+					 * a chance a window with this definition already exists!
+					 */
+					pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+					wfunc->winref = list_length(pstate->p_windowdefs);
+				}
 				break;
 			}
 		}
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index ae7d195..1eeeb97 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -482,6 +482,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..0699e18 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,12 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +287,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +298,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +323,144 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
+
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+		/*
+		 * This code is a bit messy - we want to initialize the Bitmapset in the 
+		 * partition's local memory. 
+		 */
+		null_values = bms_initialize(WinGetPartitionLocalMemory, winobj, bits_needed);
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				Bitmapset *b;
+
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* 
+				 * Update our bitmap with this result. Note the bitmap should have
+				 * been sized correctly so bms_add_member should never need to 
+				 * re-allocate a larger chunk of memory.
+				 */
+				b = bms_add_member(null_values, HAVESCANNED_INDEX(scanning));
+				Assert(b == null_values);
+				if (isnull)
+				{					
+					b = bms_add_member(null_values, ISNULL_INDEX(scanning));
+					Assert(b == null_values);
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..4700c00 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -93,4 +93,10 @@ extern int	bms_first_member(Bitmapset *a);
 /* support for hashtables using Bitmapsets as keys: */
 extern uint32 bms_hash_value(const Bitmapset *a);
 
+/* initialize a Bitmapset using a custom memory allocator */
+extern Bitmapset *bms_initialize(
+	void *(*allocator) (void *arg, Size sz),	/* function pointer to the allocator */
+	void *arg,									/* passed through to the first argument to the allocator */
+	int64 nbits);								/* the maximum capacity of the Bitmapset */
+
 #endif   /* BITMAPSET_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..71b44d5 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -435,6 +435,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..3b4ce54 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -1020,5 +1022,165 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..665abcb 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -264,5 +266,47 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..740e713 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12416,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..76244ac 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2002,6 +2002,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..4713574 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -866,3 +866,34 @@ bms_hash_value(const Bitmapset *a)
 	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
 								   (lastword + 1) * sizeof(bitmapword)));
 }
+
+/* 
+ * bms_initialize - initialize a Bitmapset using a custom memory allocator
+ *
+ * allocator
+ *		A function pointer that will be called once to initialize the
+ *		required amount of (zeroed-out) memory
+ * allocator_arg
+ *		An argument that will be passed unmodified to the allocator 
+ * 		function. Use this to pass any state the allocator requires.
+ * nbits
+ * 		The maximum capacity of the Bitmapset. An int64 as a Bitmapset with
+ * 		INT_MAX words can store more than INT_MAX bits.
+ */
+Bitmapset *
+bms_initialize(
+	void *(*allocator) (void *arg, Size sz),
+	void *allocator_arg,
+	int64 nbits)
+{
+	int nwords;
+	Bitmapset * b;
+
+	nwords = (nbits / BITS_PER_BITMAPWORD) + 1;
+	b = (Bitmapset *) allocator(allocator_arg, BITMAPSET_SIZE(nwords));
+
+	/* set up the Bitmapset's state */
+	b->nwords = nwords;
+
+	return b;
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 7380618..592899f 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -572,8 +572,7 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
@@ -582,7 +581,32 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 			winref++;
 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
 			{
-				wfunc->winref = winref;
+				/*
+				 * This is the window we want - but we may have to tweak the
+				 * definition slightly (e.g. to support the IGNORE NULLS
+				 * frame option). If so, create a 'child' (using refname
+				 * to inherit everything from the parent) that just
+				 * overrides the frame options.
+				 */
+				if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+					wfunc->winref = winref;
+				else
+				{
+					WindowDef *clone = makeNode(WindowDef);
+
+					clone->refname = pstrdup(refwin->name);
+					clone->frameOptions = windef->frameOptions; /* Note windef! */
+					clone->startOffset = copyObject(refwin->startOffset);
+					clone->endOffset = copyObject(refwin->endOffset);
+					clone->location = refwin->location;
+
+					/*
+					 * Add this new definition to the list. Note that there's
+					 * a chance a window with this definition already exists!
+					 */
+					pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+					wfunc->winref = list_length(pstate->p_windowdefs);
+				}
 				break;
 			}
 		}
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index ae7d195..1eeeb97 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -482,6 +482,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index a1ed781..5dcd4d6 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -7461,7 +7461,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		appendStringInfoChar(buf, '*');
 	else
 		get_rule_expr((Node *) wfunc->args, context, true);
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7469,6 +7469,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..0699e18 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -25,6 +26,12 @@ typedef struct rank_context
 } rank_context;
 
 /*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
+/*
  * ntile process information
  */
 typedef struct
@@ -280,7 +287,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +298,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,12 +323,144 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls)
+	{
+		int64 bits_needed, scanning, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 */
+
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+		/*
+		 * This code is a bit messy - we want to initialize the Bitmapset in the 
+		 * partition's local memory. 
+		 */
+		null_values = bms_initialize(WinGetPartitionLocalMemory, winobj, bits_needed);
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				Bitmapset *b;
+
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* 
+				 * Update our bitmap with this result. Note the bitmap should have
+				 * been sized correctly so bms_add_member should never need to 
+				 * re-allocate a larger chunk of memory.
+				 */
+				b = bms_add_member(null_values, HAVESCANNED_INDEX(scanning));
+				Assert(b == null_values);
+				if (isnull)
+				{					
+					b = bms_add_member(null_values, ISNULL_INDEX(scanning));
+					Assert(b == null_values);
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..4700c00 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -93,4 +93,10 @@ extern int	bms_first_member(Bitmapset *a);
 /* support for hashtables using Bitmapsets as keys: */
 extern uint32 bms_hash_value(const Bitmapset *a);
 
+/* initialize a Bitmapset using a custom memory allocator */
+extern Bitmapset *bms_initialize(
+	void *(*allocator) (void *arg, Size sz),	/* function pointer to the allocator */
+	void *arg,									/* passed through to the first argument to the allocator */
+	int64 nbits);								/* the maximum capacity of the Bitmapset */
+
 #endif   /* BITMAPSET_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..b50701f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -398,19 +398,33 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ * 		VIRTUAL: 
+ * 			If NULL, then the parent's (refname) value is used.
+ * 		MANDATORY:
+ * 			Never inherited from the parent, so must be specified - 
+ * 			but can be NULL.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [VIRTUAL] */
+	List	   *orderClause;
+	/* frame_clause options, see below  [MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -435,6 +449,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..05d36c5 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
-                                    pg_get_viewdef                                     
----------------------------------------------------------------------------------------
-  SELECT i.i,                                                                         +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+                                     pg_get_viewdef                                      
+-----------------------------------------------------------------------------------------
+  SELECT i.i,                                                                           +
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER (w) AS lagged_by_2                                   +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1020,5 +1031,165 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..ef2842d 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -264,5 +273,47 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7c009d8..740e713 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12275,6 +12275,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12289,7 +12290,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12302,6 +12305,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12316,7 +12320,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12410,11 +12416,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index d9f0e79..76244ac 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2002,6 +2002,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..4713574 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -866,3 +866,34 @@ bms_hash_value(const Bitmapset *a)
 	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
 								   (lastword + 1) * sizeof(bitmapword)));
 }
+
+/* 
+ * bms_initialize - initialize a Bitmapset using a custom memory allocator
+ *
+ * allocator
+ *		A function pointer that will be called once to initialize the
+ *		required amount of (zeroed-out) memory
+ * allocator_arg
+ *		An argument that will be passed unmodified to the allocator 
+ * 		function. Use this to pass any state the allocator requires.
+ * nbits
+ * 		The maximum capacity of the Bitmapset. An int64 as a Bitmapset with
+ * 		INT_MAX words can store more than INT_MAX bits.
+ */
+Bitmapset *
+bms_initialize(
+	void *(*allocator) (void *arg, Size sz),
+	void *allocator_arg,
+	int64 nbits)
+{
+	int nwords;
+	Bitmapset * b;
+
+	nwords = (nbits / BITS_PER_BITMAPWORD) + 1;
+	b = (Bitmapset *) allocator(allocator_arg, BITMAPSET_SIZE(nwords));
+
+	/* set up the Bitmapset's state */
+	b->nwords = nwords;
+
+	return b;
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c41f1b5..917e233 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -545,7 +546,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -575,7 +576,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11782,16 +11783,25 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
 					n->location = @2;
@@ -12770,6 +12780,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12858,6 +12869,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 7380618..4c6fb46 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -569,28 +569,76 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			refwin = (WindowDef *) lfirst(lc);
 			winref++;
-			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
-			{
-				wfunc->winref = winref;
+			if (refwin->name && strcmp(refwin->name, windef->name) == 0)		
 				break;
-			}
 		}
+
 		if (lc == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+			wfunc->winref = winref;
+		else
+		{
+			/*
+			 * This is the window we want - but we have to tweak the
+			 * definition slightly (e.g. to support the IGNORE NULLS
+			 * frame option) as we're not using the default (i.e. parent)
+			 * frame options. 
+			 * 
+			 * We'll create a 'child' (using refname to inherit everything 
+			 * from the parent) that just overrides the frame options
+			 * (assuming it doesn't already exist):
+			 */
+			WindowDef *clone = makeNode(WindowDef);
+
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			/*
+			 * Add this new definition to the list. Note that there's
+			 * a chance a window with this definition already exists!
+			 */
+			winref = 0;
+			foreach(lc, pstate->p_windowdefs)
+			{
+				refwin = (WindowDef *) lfirst(lc);
+
+				winref++;
+				if (refwin->refname &&
+					strcmp(refwin->refname, clone->refname) == 0 &&
+					equal(refwin->partitionClause, clone->partitionClause) &&
+					equal(refwin->orderClause, clone->orderClause) &&
+					refwin->frameOptions == clone->frameOptions &&
+					equal(refwin->startOffset, clone->startOffset) &&
+					equal(refwin->endOffset, clone->endOffset))
+				{
+					/* found a duplicate window specification */
+					wfunc->winref = winref;
+					break;
+				}
+			}
+			if (lc == NULL)			/* didn't find it? */
+			{
+				pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+				wfunc->winref = list_length(pstate->p_windowdefs);
+			}
+		}
 	}
 	else
 	{
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index ae7d195..1eeeb97 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -482,6 +482,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index a1ed781..8d0509a 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4762,11 +4762,15 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -4848,7 +4852,20 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
-	appendStringInfoChar(buf, ')');
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags relevant
+	 * instide the window def's ()s, then we'll be left with "(<refname>)".
+	 * We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1; /* the leading "(" */
+	}
+	else
+		appendStringInfoChar(buf, ')');
 }
 
 /* ----------
@@ -7461,7 +7478,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		appendStringInfoChar(buf, '*');
 	else
 		get_rule_expr((Node *) wfunc->args, context, true);
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7469,6 +7486,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..c03b831 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -24,6 +25,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;		/* the index of the lead / lagged value */
+} leadlag_const_context;
+	
+/*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +293,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +304,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +329,235 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls && !const_offset)
+	{
+		int64 bits_needed, scanning, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 * 
+		 * As the offset isn't constant we need efficient random access to the
+		 * partition, as we'll check upto O(partition size) tuples for each row
+		 * we're calculating the window function value for.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+		/*
+		 * This code is a bit messy - we want to initialize the Bitmapset in the 
+		 * partition's local memory. 
+		 */
+		null_values = bms_initialize(WinGetPartitionLocalMemory, winobj, bits_needed);
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				Bitmapset *b;
+
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* 
+				 * Update our bitmap with this result. Note the bitmap should have
+				 * been sized correctly so bms_add_member should never need to 
+				 * re-allocate a larger chunk of memory.
+				 */
+				b = bms_add_member(null_values, HAVESCANNED_INDEX(scanning));
+				Assert(b == null_values);
+				if (isnull)
+				{					
+					b = bms_add_member(null_values, ISNULL_INDEX(scanning));
+					Assert(b == null_values);
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else if (ignore_nulls /* && const_offset */)
+	{
+		/*
+		 * We can process a constant offset much more efficiently; initially
+		 * we'll scan through the first <offset> non-null rows, and store that
+		 * index. On subsequent rows we'll decide whether to push that index 
+		 * forwards to the next non-null value, or just return it again.
+		 */
+		leadlag_const_context *context = WinGetPartitionLocalMemory(
+			winobj,
+			sizeof(leadlag_const_context));
+		int count_forward = 0;
+
+		/*
+		 * Set the forward flag based on the direction of traversal - remember
+		 * we can have a LEAD or LAG of -1, and that should be equivalent to
+		 * a LAG or LEAD of 1 respectively.
+		 */
+		forward = offset == 0 ? forward : (offset > 0);
+
+		if (WinGetCurrentPosition(winobj) == 0)
+			if (forward)
+				count_forward = offset;
+			else
+				context->next = offset; /* LAG, so offset is negative */
+		else
+		{
+			/*
+			 * LEADs and LAGs are actually pretty similar - the decision of
+			 * whether or not to push our offset value forwards depends on
+			 * the current row (for LEADs) or the previous row (for LAGs) is
+			 * NULL - hence the (forward ? 0 : -1) below.
+			 */
+			result = WinGetFuncArgInPartition(winobj, 0,
+							  forward ? 0 : -1,
+							  WINDOW_SEEK_CURRENT,
+							  forward,
+							  &isnull, &isout);
+			if (!isnull)
+				count_forward = 1;
+		}
+
+		/* 
+		 * Count forward through the rows, skipping nulls and terminating if
+		 * we run off the end of the window.
+		 */
+		for (; count_forward > 0 && !isout; --count_forward)
+		{
+		 	do
+		 	{
+		 		/*
+		 		 * Conveniently, calling WinGetFuncArgInPartition with an 
+		 		 * absolute index less than zero (correctly) sets isout 
+		 		 * and isnull to true 
+		 		 */
+		 		result = WinGetFuncArgInPartition(winobj, 0,
+								  ++(context->next),
+								  WINDOW_SEEK_HEAD,
+								  !forward,
+								  &isnull, &isout);
+		 	}
+		 	while (isnull && !isout);
+		 }
+
+ 		result = WinGetFuncArgInPartition(winobj, 0,
+						  context->next,
+						  WINDOW_SEEK_HEAD,
+						  !forward,
+						  &isnull, &isout);
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/* 
+			 * Don't return whatever's lying around in result, force the output
+			 * to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..4700c00 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -93,4 +93,10 @@ extern int	bms_first_member(Bitmapset *a);
 /* support for hashtables using Bitmapsets as keys: */
 extern uint32 bms_hash_value(const Bitmapset *a);
 
+/* initialize a Bitmapset using a custom memory allocator */
+extern Bitmapset *bms_initialize(
+	void *(*allocator) (void *arg, Size sz),	/* function pointer to the allocator */
+	void *arg,									/* passed through to the first argument to the allocator */
+	int64 nbits);								/* the maximum capacity of the Bitmapset */
+
 #endif   /* BITMAPSET_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 6723647..2ada2f6 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -398,19 +398,35 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ * 		VIRTUAL: 
+ * 			If NULL, then the parent's (refname) value is used.
+ * 		MANDATORY:
+ * 			Never inherited from the parent, so must be specified - 
+ * 			but can be NULL.
+ * 		SUPER:
+ * 			Always inherited from parent, any local version ignored.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [SUPER] */
+	List	   *orderClause;
+	/* frame_clause options, see below  [MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -435,6 +451,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index b3d72a9..dd7396e 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -179,6 +179,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -312,6 +313,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index ecc1c2c..38768e3 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
-                                    pg_get_viewdef                                     
----------------------------------------------------------------------------------------
-  SELECT i.i,                                                                         +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+                                     pg_get_viewdef                                      
+-----------------------------------------------------------------------------------------
+  SELECT i.i,                                                                           +
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER w AS lagged_by_2                                     +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1020,5 +1031,165 @@ 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
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 769be0f..ef2842d 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -264,5 +273,47 @@ SELECT ntile(0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
 SELECT nth_value(four, 0) OVER (ORDER BY ten), ten, four FROM tenk1;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 425544a..a3babed 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12295,6 +12295,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12309,7 +12310,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12322,6 +12325,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12336,7 +12340,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12430,11 +12436,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index bbc5336..3b69ac1 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2016,6 +2016,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..4713574 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -866,3 +866,34 @@ bms_hash_value(const Bitmapset *a)
 	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
 								   (lastword + 1) * sizeof(bitmapword)));
 }
+
+/* 
+ * bms_initialize - initialize a Bitmapset using a custom memory allocator
+ *
+ * allocator
+ *		A function pointer that will be called once to initialize the
+ *		required amount of (zeroed-out) memory
+ * allocator_arg
+ *		An argument that will be passed unmodified to the allocator 
+ * 		function. Use this to pass any state the allocator requires.
+ * nbits
+ * 		The maximum capacity of the Bitmapset. An int64 as a Bitmapset with
+ * 		INT_MAX words can store more than INT_MAX bits.
+ */
+Bitmapset *
+bms_initialize(
+	void *(*allocator) (void *arg, Size sz),
+	void *allocator_arg,
+	int64 nbits)
+{
+	int nwords;
+	Bitmapset * b;
+
+	nwords = (nbits / BITS_PER_BITMAPWORD) + 1;
+	b = (Bitmapset *) allocator(allocator_arg, BITMAPSET_SIZE(nwords));
+
+	/* set up the Bitmapset's state */
+	b->nwords = nwords;
+
+	return b;
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 22e82ba..9073f90 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -546,7 +547,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -576,7 +577,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11553,19 +11554,28 @@ filter_clause:
              | /*EMPTY*/                            { $$ = NULL; }
          ;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
-					n->location = @2;
+					n->location = @3;
 					$$ = n;
 				}
 			| /*EMPTY*/
@@ -12542,6 +12552,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12631,6 +12642,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 4e4e1cd..51fc6ca 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -579,28 +579,76 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			refwin = (WindowDef *) lfirst(lc);
 			winref++;
-			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
-			{
-				wfunc->winref = winref;
+			if (refwin->name && strcmp(refwin->name, windef->name) == 0)		
 				break;
-			}
 		}
+
 		if (lc == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+			wfunc->winref = winref;
+		else
+		{
+			/*
+			 * This is the window we want - but we have to tweak the
+			 * definition slightly (e.g. to support the IGNORE NULLS
+			 * frame option) as we're not using the default (i.e. parent)
+			 * frame options. 
+			 * 
+			 * We'll create a 'child' (using refname to inherit everything 
+			 * from the parent) that just overrides the frame options
+			 * (assuming it doesn't already exist):
+			 */
+			WindowDef *clone = makeNode(WindowDef);
+
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			/*
+			 * Add this new definition to the list. Note that there's
+			 * a chance a window with this definition already exists!
+			 */
+			winref = 0;
+			foreach(lc, pstate->p_windowdefs)
+			{
+				refwin = (WindowDef *) lfirst(lc);
+
+				winref++;
+				if (refwin->refname &&
+					strcmp(refwin->refname, clone->refname) == 0 &&
+					equal(refwin->partitionClause, clone->partitionClause) &&
+					equal(refwin->orderClause, clone->orderClause) &&
+					refwin->frameOptions == clone->frameOptions &&
+					equal(refwin->startOffset, clone->startOffset) &&
+					equal(refwin->endOffset, clone->endOffset))
+				{
+					/* found a duplicate window specification */
+					wfunc->winref = winref;
+					break;
+				}
+			}
+			if (lc == NULL)			/* didn't find it? */
+			{
+				pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+				wfunc->winref = list_length(pstate->p_windowdefs);
+			}
+		}
 	}
 	else
 	{
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1f02c9a..8a7f867 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -518,6 +518,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("FILTER is not implemented in non-aggregate window functions"),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2b005d6..6c222a3 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4778,11 +4778,15 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -4864,7 +4868,20 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
-	appendStringInfoChar(buf, ')');
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags relevant
+	 * inside the window def's ()s, then we'll be left with "(<refname>)".
+	 * We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1; /* the trailing ")" */
+	}
+	else
+		appendStringInfoChar(buf, ')');
 }
 
 /* ----------
@@ -7493,7 +7510,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7501,6 +7518,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..c03b831 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -24,6 +25,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;		/* the index of the lead / lagged value */
+} leadlag_const_context;
+	
+/*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +293,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +304,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +329,235 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls && !const_offset)
+	{
+		int64 bits_needed, scanning, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 * 
+		 * As the offset isn't constant we need efficient random access to the
+		 * partition, as we'll check upto O(partition size) tuples for each row
+		 * we're calculating the window function value for.
+		 */
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+		/*
+		 * This code is a bit messy - we want to initialize the Bitmapset in the 
+		 * partition's local memory. 
+		 */
+		null_values = bms_initialize(WinGetPartitionLocalMemory, winobj, bits_needed);
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				Bitmapset *b;
+
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
 									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* 
+				 * Update our bitmap with this result. Note the bitmap should have
+				 * been sized correctly so bms_add_member should never need to 
+				 * re-allocate a larger chunk of memory.
+				 */
+				b = bms_add_member(null_values, HAVESCANNED_INDEX(scanning));
+				Assert(b == null_values);
+				if (isnull)
+				{					
+					b = bms_add_member(null_values, ISNULL_INDEX(scanning));
+					Assert(b == null_values);
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else if (ignore_nulls /* && const_offset */)
+	{
+		/*
+		 * We can process a constant offset much more efficiently; initially
+		 * we'll scan through the first <offset> non-null rows, and store that
+		 * index. On subsequent rows we'll decide whether to push that index 
+		 * forwards to the next non-null value, or just return it again.
+		 */
+		leadlag_const_context *context = WinGetPartitionLocalMemory(
+			winobj,
+			sizeof(leadlag_const_context));
+		int count_forward = 0;
+
+		/*
+		 * Set the forward flag based on the direction of traversal - remember
+		 * we can have a LEAD or LAG of -1, and that should be equivalent to
+		 * a LAG or LEAD of 1 respectively.
+		 */
+		forward = offset == 0 ? forward : (offset > 0);
+
+		if (WinGetCurrentPosition(winobj) == 0)
+			if (forward)
+				count_forward = offset;
+			else
+				context->next = offset; /* LAG, so offset is negative */
+		else
+		{
+			/*
+			 * LEADs and LAGs are actually pretty similar - the decision of
+			 * whether or not to push our offset value forwards depends on
+			 * the current row (for LEADs) or the previous row (for LAGs) is
+			 * NULL - hence the (forward ? 0 : -1) below.
+			 */
+			result = WinGetFuncArgInPartition(winobj, 0,
+							  forward ? 0 : -1,
+							  WINDOW_SEEK_CURRENT,
+							  forward,
+							  &isnull, &isout);
+			if (!isnull)
+				count_forward = 1;
+		}
+
+		/* 
+		 * Count forward through the rows, skipping nulls and terminating if
+		 * we run off the end of the window.
+		 */
+		for (; count_forward > 0 && !isout; --count_forward)
+		{
+		 	do
+		 	{
+		 		/*
+		 		 * Conveniently, calling WinGetFuncArgInPartition with an 
+		 		 * absolute index less than zero (correctly) sets isout 
+		 		 * and isnull to true 
+		 		 */
+		 		result = WinGetFuncArgInPartition(winobj, 0,
+								  ++(context->next),
+								  WINDOW_SEEK_HEAD,
+								  !forward,
+								  &isnull, &isout);
+		 	}
+		 	while (isnull && !isout);
+		 }
+
+ 		result = WinGetFuncArgInPartition(winobj, 0,
+						  context->next,
+						  WINDOW_SEEK_HEAD,
+						  !forward,
+						  &isnull, &isout);
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/* 
+			 * Don't return whatever's lying around in result, force the output
+			 * to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..4700c00 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -93,4 +93,10 @@ extern int	bms_first_member(Bitmapset *a);
 /* support for hashtables using Bitmapsets as keys: */
 extern uint32 bms_hash_value(const Bitmapset *a);
 
+/* initialize a Bitmapset using a custom memory allocator */
+extern Bitmapset *bms_initialize(
+	void *(*allocator) (void *arg, Size sz),	/* function pointer to the allocator */
+	void *arg,									/* passed through to the first argument to the allocator */
+	int64 nbits);								/* the maximum capacity of the Bitmapset */
+
 #endif   /* BITMAPSET_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 51fef68..d27ca5f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -406,19 +406,35 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ * 		VIRTUAL: 
+ * 			If NULL, then the parent's (refname) value is used.
+ * 		MANDATORY:
+ * 			Never inherited from the parent, so must be specified - 
+ * 			but can be NULL.
+ * 		SUPER:
+ * 			Always inherited from parent, any local version ignored.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [SUPER] */
+	List	   *orderClause;
+	/* frame_clause options, see below  [MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -443,6 +459,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 8bd34d6..9196b41 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -180,6 +180,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -314,6 +315,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 7b31d13..5926a72 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
-                                    pg_get_viewdef                                     
----------------------------------------------------------------------------------------
-  SELECT i.i,                                                                         +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+                                     pg_get_viewdef                                      
+-----------------------------------------------------------------------------------------
+  SELECT i.i,                                                                           +
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER w AS lagged_by_2                                     +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1033,5 +1044,165 @@ FROM empsalary GROUP BY depname;
  25100 |          1 |        22600 | develop
 (3 rows)
 
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6ee3696..cda112f 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -272,5 +281,48 @@ SELECT sum(salary), row_number() OVER (ORDER BY depname), sum(
     depname
 FROM empsalary GROUP BY depname;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+
+

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 425544a..a3babed 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12295,6 +12295,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12309,7 +12310,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12322,6 +12325,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12336,7 +12340,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12430,11 +12436,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index bbc5336..3b69ac1 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2016,6 +2016,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ * 		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..4713574 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -866,3 +866,34 @@ bms_hash_value(const Bitmapset *a)
 	return DatumGetUInt32(hash_any((const unsigned char *) a->words,
 								   (lastword + 1) * sizeof(bitmapword)));
 }
+
+/* 
+ * bms_initialize - initialize a Bitmapset using a custom memory allocator
+ *
+ * allocator
+ *		A function pointer that will be called once to initialize the
+ *		required amount of (zeroed-out) memory
+ * allocator_arg
+ *		An argument that will be passed unmodified to the allocator 
+ * 		function. Use this to pass any state the allocator requires.
+ * nbits
+ * 		The maximum capacity of the Bitmapset. An int64 as a Bitmapset with
+ * 		INT_MAX words can store more than INT_MAX bits.
+ */
+Bitmapset *
+bms_initialize(
+	void *(*allocator) (void *arg, Size sz),
+	void *allocator_arg,
+	int64 nbits)
+{
+	int nwords;
+	Bitmapset * b;
+
+	nwords = (nbits / BITS_PER_BITMAPWORD) + 1;
+	b = (Bitmapset *) allocator(allocator_arg, BITMAPSET_SIZE(nwords));
+
+	/* set up the Bitmapset's state */
+	b->nwords = nwords;
+
+	return b;
+}
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 22e82ba..9073f90 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -546,7 +547,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -576,7 +577,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11553,19 +11554,28 @@ filter_clause:
              | /*EMPTY*/                            { $$ = NULL; }
          ;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
-					n->location = @2;
+					n->location = @3;
 					$$ = n;
 				}
 			| /*EMPTY*/
@@ -12542,6 +12552,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12631,6 +12642,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 4e4e1cd..51fc6ca 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -579,28 +579,76 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			refwin = (WindowDef *) lfirst(lc);
 			winref++;
 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)		
-			{
-				wfunc->winref = winref;
 				break;
 		}
-		}
+
 		if (lc == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+			wfunc->winref = winref;
+		else
+		{
+			/*
+			 * This is the window we want - but we have to tweak the
+			 * definition slightly (e.g. to support the IGNORE NULLS
+			 * frame option) as we're not using the default (i.e. parent)
+			 * frame options. 
+			 * 
+			 * We'll create a 'child' (using refname to inherit everything 
+			 * from the parent) that just overrides the frame options
+			 * (assuming it doesn't already exist):
+			 */
+			WindowDef *clone = makeNode(WindowDef);
+
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			/*
+			 * Add this new definition to the list. Note that there's
+			 * a chance a window with this definition already exists!
+			 */
+			winref = 0;
+			foreach(lc, pstate->p_windowdefs)
+			{
+				refwin = (WindowDef *) lfirst(lc);
+
+				winref++;
+				if (refwin->refname &&
+					strcmp(refwin->refname, clone->refname) == 0 &&
+					equal(refwin->partitionClause, clone->partitionClause) &&
+					equal(refwin->orderClause, clone->orderClause) &&
+					refwin->frameOptions == clone->frameOptions &&
+					equal(refwin->startOffset, clone->startOffset) &&
+					equal(refwin->endOffset, clone->endOffset))
+				{
+					/* found a duplicate window specification */
+					wfunc->winref = winref;
+					break;
+				}
+			}
+			if (lc == NULL)			/* didn't find it? */
+			{
+				pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+				wfunc->winref = list_length(pstate->p_windowdefs);
+			}
+		}
 	}
 	else
 	{
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 1f02c9a..8a7f867 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -518,6 +518,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("FILTER is not implemented in non-aggregate window functions"),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/* 
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+			|| (strcmp("lead", strVal(llast(funcname))) != 0 && 
+			    strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+					 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 2b005d6..6c222a3 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4778,11 +4778,15 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -4864,6 +4868,19 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags relevant
+	 * inside the window def's ()s, then we'll be left with "(<refname>)".
+	 * We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1; /* the trailing ")" */
+	}
+	else
 		appendStringInfoChar(buf, ')');
 }
 
@@ -7493,7 +7510,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7501,6 +7518,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..187ed94 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -24,6 +25,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;		/* the index of the lead / lagged value */
+} leadlag_const_context;
+	
+/*
+ * lead-lag process helpers
+ */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +293,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ * 	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +304,18 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+	Bitmapset*	null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as 
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't
+	 * mark at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +329,239 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if(!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls && !const_offset)
+	{
+		int64 bits_needed, scanning, current = WinGetCurrentPosition(winobj);
+		bool scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't exist".
+		 * This means that we'll scan from the current row an 'offset' number of
+		 * non-null rows, and then return that one.
+		 * 
+		 * As the offset isn't constant we need efficient random access to the
+		 * partition, as we'll check upto O(partition size) tuples for each row
+		 * we're calculating the window function value for.
+		 */
+
+		 /*
+		  * Accessing tuples is expensive, so we'll keep track of the ones we've
+		  * accessed (more specifically, if they're null or not). We'll need one
+		  * bit for whether the value is null and one bit for whether we've checked
+		  * that tuple or not. We'll keep these two bits together (as opposed to 
+		  * having two separate bitmaps) to improve cache locality.
+		  */
+		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+		/*
+		 * This code is a bit messy - we want to initialize the Bitmapset in the 
+		 * partition's local memory. 
+		 */
+		null_values = bms_initialize(
+			(void *(*) (void *arg, Size sz)) WinGetPartitionLocalMemory, 
+			winobj, 
+			bits_needed);
+
+		/* 
+		 * We use offset >= 0 instead of just forward as the offset might be in the
+		 * opposite direction to the way we're scanning. We'll then force offset to
+		 * be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the default
+				 * value, but not whatever's left in result. We'll use the isnull
+				 * flag to say "ignore it"!
+				 */
+				isnull = true;
+				result = (Datum) 0;
+
+				break;
+			}
+
+			/* look in the bitmap cache - do we know if this index is null? */
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), null_values);
+			}
+			else
+			{
+				Bitmapset *b;
+
+				/* first time we've accessed this index; let's see if it's null: */
+				result = WinGetFuncArgInPartition(winobj, 0,
+									  scanning,
+									  WINDOW_SEEK_HEAD,
+									  false,
+									  &isnull, &isout);
+				if (isout)
+					break;
+
+				/* 
+				 * Update our bitmap with this result. Note the bitmap should have
+				 * been sized correctly so bms_add_member should never need to 
+				 * re-allocate a larger chunk of memory.
+				 */
+				b = bms_add_member(null_values, HAVESCANNED_INDEX(scanning));
+				Assert(b == null_values);
+				if (isnull)
+				{					
+					b = bms_add_member(null_values, ISNULL_INDEX(scanning));
+					Assert(b == null_values);
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a chance 
+			 * that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+			 	if (offset == 0)
+			 	{
+					result = WinGetFuncArgInPartition(winobj, 0,
+										  scanning,
+										  WINDOW_SEEK_HEAD,
+										  false,
+										  &isnull, &isout);
+					break;
+				}
+				else
+					--offset; /* it's not null, so we're one step closer to the value we want */	
+			}
+			else if (scanning == current)
+			{
+				/*
+				 * A slight edge case. Consider:
+				 *
+				 * ----------
+				 *   A   | lag(A, 1)
+				 *   1   |   NULL
+				 *   2   |    1
+				 *  NULL |    ?
+				 * ----------
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 */
+				--offset;
+			}
+		}
+	}
+	else if (ignore_nulls /* && const_offset */)
+	{
+		/*
+		 * We can process a constant offset much more efficiently; initially
+		 * we'll scan through the first <offset> non-null rows, and store that
+		 * index. On subsequent rows we'll decide whether to push that index 
+		 * forwards to the next non-null value, or just return it again.
+		 */
+		leadlag_const_context *context = WinGetPartitionLocalMemory(
+			winobj,
+			sizeof(leadlag_const_context));
+		int count_forward = 0;
+
+		/*
+		 * Set the forward flag based on the direction of traversal - remember
+		 * we can have a LEAD or LAG of -1, and that should be equivalent to
+		 * a LAG or LEAD of 1 respectively.
+		 */
+		forward = offset == 0 ? forward : (offset > 0);
+
+		if (WinGetCurrentPosition(winobj) == 0)
+			if (forward)
+				count_forward = offset;
+			else
+				context->next = offset; /* LAG, so offset is negative */
+		else
+		{
+			/*
+			 * LEADs and LAGs are actually pretty similar - the decision of
+			 * whether or not to push our offset value forwards depends on
+			 * the current row (for LEADs) or the previous row (for LAGs) is
+			 * NULL - hence the (forward ? 0 : -1) below.
+			 */
+			result = WinGetFuncArgInPartition(winobj, 0,
+							  forward ? 0 : -1,
+							  WINDOW_SEEK_CURRENT,
+							  forward,
+							  &isnull, &isout);
+			if (!isnull)
+				count_forward = 1;
+		}
+
+		/* 
+		 * Count forward through the rows, skipping nulls and terminating if
+		 * we run off the end of the window.
+		 */
+		for (; count_forward > 0 && !isout; --count_forward)
+		{
+		 	do
+		 	{
+		 		/*
+		 		 * Conveniently, calling WinGetFuncArgInPartition with an 
+		 		 * absolute index less than zero (correctly) sets isout 
+		 		 * and isnull to true 
+		 		 */
+		 		result = WinGetFuncArgInPartition(winobj, 0,
+								  ++(context->next),
+								  WINDOW_SEEK_HEAD,
+								  !forward,
+								  &isnull, &isout);
+		 	}
+		 	while (isnull && !isout);
+		 }
 
  		result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
+						  context->next,
+						  WINDOW_SEEK_HEAD,
+						  !forward,
+						  &isnull, &isout);
+	}
+	else
+	{
+		/* 
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
 										  WINDOW_SEEK_CURRENT,
 										  const_offset,
 										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/* 
+			 * Don't return whatever's lying around in result, force the output
+			 * to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/bitmapset.h b/src/include/nodes/bitmapset.h
index 2a4b41d..4700c00 100644
--- a/src/include/nodes/bitmapset.h
+++ b/src/include/nodes/bitmapset.h
@@ -93,4 +93,10 @@ extern int	bms_first_member(Bitmapset *a);
 /* support for hashtables using Bitmapsets as keys: */
 extern uint32 bms_hash_value(const Bitmapset *a);
 
+/* initialize a Bitmapset using a custom memory allocator */
+extern Bitmapset *bms_initialize(
+	void *(*allocator) (void *arg, Size sz),	/* function pointer to the allocator */
+	void *arg,									/* passed through to the first argument to the allocator */
+	int64 nbits);								/* the maximum capacity of the Bitmapset */
+
 #endif   /* BITMAPSET_H */
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 51fef68..d27ca5f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -406,19 +406,35 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ * 		VIRTUAL: 
+ * 			If NULL, then the parent's (refname) value is used.
+ * 		MANDATORY:
+ * 			Never inherited from the parent, so must be specified - 
+ * 			but can be NULL.
+ * 		SUPER:
+ * 			Always inherited from parent, any local version ignored.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [SUPER] */
+	List	   *orderClause;
+	/* frame_clause options, see below  [MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -443,6 +459,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS                0x04000 
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 8bd34d6..9196b41 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -180,6 +180,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -314,6 +315,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..81f5ba0 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 7b31d13..5926a72 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
                                      pg_get_viewdef                                      
----------------------------------------------------------------------------------------
+-----------------------------------------------------------------------------------------
   SELECT i.i,                                                                           +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER w AS lagged_by_2                                     +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1033,5 +1044,165 @@ FROM empsalary GROUP BY depname;
  25100 |          1 |        22600 | develop
 (3 rows)
 
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6ee3696..cda112f 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -272,5 +281,48 @@ SELECT sum(salary), row_number() OVER (ORDER BY depname), sum(
     depname
 FROM empsalary GROUP BY depname;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+
+

diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..7b4d4db 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -634,17 +634,8 @@ bms_add_member(Bitmapset *a, int x)
 	bitnum = BITNUM(x);
 	if (wordnum >= a->nwords)
 	{
-		/* Slow path: make a larger set and union the input set into it */
-		Bitmapset  *result;
-		int			nwords;
-		int			i;
-
-		result = bms_make_singleton(x);
-		nwords = a->nwords;
-		for (i = 0; i < nwords; i++)
-			result->words[i] |= a->words[i];
-		pfree(a);
-		return result;
+		a = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(wordnum + 1));
+		a->nwords = wordnum + 1;
 	}
 	/* Fast path: x fits in existing set */
 	a->words[wordnum] |= ((bitmapword) 1 << bitnum);

>From ee01d848f39400c8524c66944ada6fde47894978 Mon Sep 17 00:00:00 2001
From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Mon, 30 Sep 2013 16:37:00 +0300
Subject: [PATCH 1/1] In bms_add_member(), use repalloc() if the bms needs to
 be enlarged.

Previously bms_add_member() would palloc a whole-new copy of the existing
set, copy the words, and pfree the old one. repalloc() is potentially much
faster, and more importantly, this is less surprising if CurrentMemoryContext
is not the same as the context the old set is in. bms_add_member() still
allocates a new bitmapset in CurrentMemoryContext if NULL is passed as
argument, but that is a lot less likely to induce bugs.

Nicholas White.
---
 src/backend/nodes/bitmapset.c | 19 +++++++++----------
 1 file changed, 9 insertions(+), 10 deletions(-)

diff --git a/src/backend/nodes/bitmapset.c b/src/backend/nodes/bitmapset.c
index b18b7a5..540db16 100644
--- a/src/backend/nodes/bitmapset.c
+++ b/src/backend/nodes/bitmapset.c
@@ -632,21 +632,20 @@ bms_add_member(Bitmapset *a, int x)
 		return bms_make_singleton(x);
 	wordnum = WORDNUM(x);
 	bitnum = BITNUM(x);
+
+	/* enlarge the set if necessary */
 	if (wordnum >= a->nwords)
 	{
-		/* Slow path: make a larger set and union the input set into it */
-		Bitmapset  *result;
-		int			nwords;
+		int			oldnwords = a->nwords;
 		int			i;
 
-		result = bms_make_singleton(x);
-		nwords = a->nwords;
-		for (i = 0; i < nwords; i++)
-			result->words[i] |= a->words[i];
-		pfree(a);
-		return result;
+		a = (Bitmapset *) repalloc(a, BITMAPSET_SIZE(wordnum + 1));
+		a->nwords = wordnum + 1;
+		/* zero out the enlarged portion */
+		for (i = oldnwords; i < a->nwords; i++)
+			a->words[i] = 0;
 	}
-	/* Fast path: x fits in existing set */
+
 	a->words[wordnum] |= ((bitmapword) 1 << bitnum);
 	return a;
 }
-- 
1.8.4.rc3

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7dd1ef2..54ed0a4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12328,6 +12328,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12342,7 +12343,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12355,6 +12358,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12369,7 +12373,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12463,11 +12469,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 544ba98..fc7908b 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1981,6 +1981,18 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
  * API exposed to window functions
  ***********************************************************************/
 
+/*
+ * WinGetPartitionMemoryContext
+ *		Returns the memory context for the current partition. All
+ *		allocations done by WinGetPartitionLocalMemory are put in
+ *		this context.
+ */
+MemoryContext
+WinGetPartitionMemoryContext(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->partcontext;
+}
 
 /*
  * WinGetPartitionLocalMemory
@@ -2017,6 +2029,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ *		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a9812af..c59ab63 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -547,7 +548,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -577,7 +578,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11572,19 +11573,28 @@ filter_clause:
              | /*EMPTY*/                            { $$ = NULL; }
          ;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
-					n->location = @2;
+					n->location = @3;
 					$$ = n;
 				}
 			| /*EMPTY*/
@@ -12561,6 +12571,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12650,6 +12661,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 98cb58a..2bf0b00 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -579,28 +579,80 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			refwin = (WindowDef *) lfirst(lc);
 			winref++;
 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
-			{
-				wfunc->winref = winref;
 				break;
-			}
 		}
+
 		if (lc == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+			wfunc->winref = winref;
+		else
+		{
+			/*
+			 * This is the window we want - but we have to tweak the
+			 * definition slightly (e.g. to support the IGNORE NULLS frame
+			 * option) as we're not using the default (i.e. parent) frame
+			 * options.
+			 *
+			 * We'll create a 'child' (using refname to inherit everything
+			 * from the parent) that just overrides the frame options
+			 * (assuming it doesn't already exist):
+			 */
+			WindowDef  *clone = makeNode(WindowDef);
+
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			/*
+			 * Add this new definition to the list. Note that there's a chance
+			 * a window with this definition already exists!
+			 */
+			winref = 0;
+			foreach(lc, pstate->p_windowdefs)
+			{
+				refwin = (WindowDef *) lfirst(lc);
+
+				winref++;
+				if (refwin->refname &&
+					strcmp(refwin->refname, clone->refname) == 0 &&
+					equal(refwin->partitionClause, clone->partitionClause) &&
+					equal(refwin->orderClause, clone->orderClause) &&
+					refwin->frameOptions == clone->frameOptions &&
+					equal(refwin->startOffset, clone->startOffset) &&
+					equal(refwin->endOffset, clone->endOffset))
+				{
+					/*
+					 * found a duplicate window specification, don't need
+					 * clone
+					 */
+					wfunc->winref = winref;
+					pfree(clone);
+					break;
+				}
+			}
+			if (lc == NULL)		/* didn't find it? */
+			{
+				pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+				wfunc->winref = list_length(pstate->p_windowdefs);
+			}
+		}
 	}
 	else
 	{
@@ -819,8 +871,8 @@ check_ungrouped_columns_walker(Node *node,
 	 * If we find an aggregate call of the original level, do not recurse into
 	 * its arguments or filter; ungrouped vars there are not an error. We can
 	 * also skip looking at aggregates of higher levels, since they could not
-	 * possibly contain Vars of concern to us (see transformAggregateCall).
-	 * We do need to look at aggregates of lower levels, however.
+	 * possibly contain Vars of concern to us (see transformAggregateCall). We
+	 * do need to look at aggregates of lower levels, however.
 	 */
 	if (IsA(node, Aggref) &&
 		(int) ((Aggref *) node)->agglevelsup >= context->sublevels_up)
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 2bd24c8..7066046 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -391,13 +391,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	 */
 	if (nargs > 0 && vatype == ANYOID && func_variadic)
 	{
-		Oid		va_arr_typid = actual_arg_types[nargs - 1];
+		Oid			va_arr_typid = actual_arg_types[nargs - 1];
 
 		if (!OidIsValid(get_element_type(va_arr_typid)))
 			ereport(ERROR,
 					(errcode(ERRCODE_DATATYPE_MISMATCH),
 					 errmsg("VARIADIC argument must be an array"),
-			  parser_errposition(pstate, exprLocation((Node *) llast(fargs)))));
+			parser_errposition(pstate, exprLocation((Node *) llast(fargs)))));
 	}
 
 	/* build the appropriate output structure */
@@ -522,6 +522,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("FILTER is not implemented in non-aggregate window functions"),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/*
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+				|| (strcmp("lead", strVal(llast(funcname))) != 0 &&
+					strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+						 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9a1d12e..78b0738 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4764,11 +4764,16 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int			initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -4850,7 +4855,20 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
-	appendStringInfoChar(buf, ')');
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags
+	 * relevant inside the window def's ()s, then we'll be left with
+	 * "(<refname>)". We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1;			/* the trailing ")" */
+	}
+	else
+		appendStringInfoChar(buf, ')');
 }
 
 /* ----------
@@ -7493,7 +7511,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7501,6 +7519,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..0150886 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,6 +13,7 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
 #include "windowapi.h"
 
@@ -24,6 +25,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;			/* the index of the lead / lagged value */
+}	leadlag_const_context;
+
+/*
+ * lead-lag process helpers
+ */
+#define ISNULL_INDEX(i) (2 * (i))
+#define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +293,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ *	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +304,24 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+
+	/**
+	 * A ** pointer as we keep a Bitmapset * in the partition context, and
+	 * WinGetPartitionLocalMemory returns a pointer to whatever's in the
+	 * context.
+	 */
+	Bitmapset **null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't mark
+	 * at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +335,245 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if (!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls && !const_offset)
+	{
+		int64		scanning,
+					current = WinGetCurrentPosition(winobj);
+		bool		scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't
+		 * exist". This means that we'll scan from the current row an 'offset'
+		 * number of non-null rows, and then return that one.
+		 *
+		 * As the offset isn't constant we need efficient random access to the
+		 * partition, as we'll check upto O(partition size) tuples for each
+		 * row we're calculating the window function value for.
+		 */
+
+		null_values = (Bitmapset **) WinGetPartitionLocalMemory(winobj, sizeof(Bitmapset *));
+
+		if (*null_values == NULL)
+		{
+			MemoryContext oldcxt;
+
+			/*
+			 * Accessing tuples is expensive, so we'll keep track of the ones
+			 * we've accessed (more specifically, if they're null or not).
+			 * We'll need one bit for whether the value is null and one bit
+			 * for whether we've checked that tuple or not. We'll keep these
+			 * two bits together (as opposed to having two separate bitmaps)
+			 * to improve cache locality.
+			 *
+			 * However, we'd lose the efficient gains if we keep having to
+			 * resize the Bitmapset (by setting higher and higher bits). We
+			 * know the maximum number of bits we'll ever need, so we'll use
+			 * bms_make_singleton to force our Bitmapset up to the required
+			 * size.
+			 */
+			int64		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+			oldcxt = MemoryContextSwitchTo(WinGetPartitionMemoryContext(winobj));
+			*null_values = bms_make_singleton(bits_needed + 1);
+			MemoryContextSwitchTo(oldcxt);
+		}
+
+		/*
+		 * We use offset >= 0 instead of just forward as the offset might be
+		 * in the opposite direction to the way we're scanning. We'll then
+		 * force offset to be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the
+				 * default value, but not whatever's left in result. We'll use
+				 * the isnull flag to say "ignore it"!
+				 */
+				isnull = true;
+				result = (Datum) 0;
+
+				break;
+			}
+
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), *null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), *null_values);
+			}
+			else
+			{
+				/*
+				 * first time we've accessed this index; let's see if it's
+				 * null:
+				 */
+				result = WinGetFuncArgInPartition(winobj, 0,
+												  scanning,
+												  WINDOW_SEEK_HEAD,
+												  false,
+												  &isnull, &isout);
+				if (isout)
+					break;
+
+				bms_add_member(*null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{
+					bms_add_member(*null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a
+			 * chance that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+				if (offset == 0)
+				{
+					result = WinGetFuncArgInPartition(winobj, 0,
+													  scanning,
+													  WINDOW_SEEK_HEAD,
+													  false,
+													  &isnull, &isout);
+					break;
+				}
+				else
+					--offset;	/* it's not null, so we're one step closer to
+								 * the value we want */
+			}
+			else if (scanning == current)
+			{
+				/*--------
+				 * A slight edge case. Consider:
+				 *
+				 * =================
+				 *	 A	 | lag(A, 1)
+				 * =================
+				 *	 1	 |	 NULL
+				 *	 2	 |	  1
+				 *	NULL |	  ?
+				 * =================
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 *--------
+				 */
+				--offset;
+			}
+		}
+	}
+	else if (ignore_nulls /* && const_offset */ )
+	{
+		/*
+		 * We can process a constant offset much more efficiently; initially
+		 * we'll scan through the first <offset> non-null rows, and store that
+		 * index. On subsequent rows we'll decide whether to push that index
+		 * forwards to the next non-null value, or just return it again.
+		 */
+		leadlag_const_context *context = WinGetPartitionLocalMemory(
+																	winobj,
+											  sizeof(leadlag_const_context));
+		int			count_forward = 0;
+
+		/*
+		 * Set the forward flag based on the direction of traversal - remember
+		 * we can have a LEAD or LAG of -1, and that should be equivalent to a
+		 * LAG or LEAD of 1 respectively.
+		 */
+		forward = offset == 0 ? forward : (offset > 0);
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
-									  &isnull, &isout);
+		if (WinGetCurrentPosition(winobj) == 0)
+			if (forward)
+				count_forward = offset;
+			else
+				context->next = offset; /* LAG, so offset is negative */
+		else
+		{
+			/*
+			 * LEADs and LAGs are actually pretty similar - the decision of
+			 * whether or not to push our offset value forwards depends on the
+			 * current row (for LEADs) or the previous row (for LAGs) is NULL
+			 * - hence the (forward ? 0 : -1) below.
+			 */
+			result = WinGetFuncArgInPartition(winobj, 0,
+											  forward ? 0 : -1,
+											  WINDOW_SEEK_CURRENT,
+											  forward,
+											  &isnull, &isout);
+			if (!isnull)
+				count_forward = 1;
+		}
+
+		/*
+		 * Count forward through the rows, skipping nulls and terminating if
+		 * we run off the end of the window.
+		 */
+		for (; count_forward > 0 && !isout; --count_forward)
+		{
+			do
+			{
+				/*
+				 * Conveniently, calling WinGetFuncArgInPartition with an
+				 * absolute index less than zero (correctly) sets isout and
+				 * isnull to true
+				 */
+				result = WinGetFuncArgInPartition(winobj, 0,
+												  ++(context->next),
+												  WINDOW_SEEK_HEAD,
+												  !forward,
+												  &isnull, &isout);
+			}
+			while (isnull && !isout);
+		}
+
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  context->next,
+										  WINDOW_SEEK_HEAD,
+										  !forward,
+										  &isnull, &isout);
+	}
+	else
+	{
+		/*
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/*
+			 * Don't return whatever's lying around in result, force the
+			 * output to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 51fef68..a26fc01 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -128,7 +128,7 @@ typedef struct Query
 
 	List	   *targetList;		/* target list (of TargetEntry) */
 
-	List	   *withCheckOptions; /* a list of WithCheckOption's */
+	List	   *withCheckOptions;		/* a list of WithCheckOption's */
 
 	List	   *returningList;	/* return-values list (of TargetEntry) */
 
@@ -406,19 +406,35 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ *		VIRTUAL:
+ *			If NULL, then the parent's (refname) value is used.
+ *		MANDATORY:
+ *			Never inherited from the parent, so must be specified -
+ *			but can be NULL.
+ *		SUPER:
+ *			Always inherited from parent, any local version ignored.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [SUPER] */
+	List	   *orderClause;
+	/* frame_clause options, see below	[MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -443,6 +459,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
@@ -655,10 +672,10 @@ typedef struct XmlSerialize
  *
  *	  The same comments apply to FUNCTION RTEs when the function's return type
  *	  is a named composite type. In addition, for all return types, FUNCTION
- *    RTEs with ORDINALITY must always have the last colname entry being the
- *    one for the ordinal column; this is enforced when constructing the RTE.
- *    Thus when ORDINALITY is used, there will be exactly one more colname
- *    than would have been present otherwise.
+ *	  RTEs with ORDINALITY must always have the last colname entry being the
+ *	  one for the ordinal column; this is enforced when constructing the RTE.
+ *	  Thus when ORDINALITY is used, there will be exactly one more colname
+ *	  than would have been present otherwise.
  *
  *	  In JOIN RTEs, the colnames in both alias and eref are one-to-one with
  *	  joinaliasvars entries.  A JOIN RTE will omit columns of its inputs when
@@ -760,18 +777,18 @@ typedef struct RangeTblEntry
 	 * If the function returns an otherwise-unspecified RECORD, funccoltypes
 	 * lists the column types declared in the RTE's column type specification,
 	 * funccoltypmods lists their declared typmods, funccolcollations their
-	 * collations.  Note that in this case, ORDINALITY is not permitted, so
+	 * collations.	Note that in this case, ORDINALITY is not permitted, so
 	 * there is no extra ordinal column to be allowed for.
 	 *
-     * Otherwise, those fields are NIL, and the result column types must be
+	 * Otherwise, those fields are NIL, and the result column types must be
 	 * derived from the funcexpr while treating the ordinal column, if
-	 * present, as a special case.  (see get_rte_attribute_*)
+	 * present, as a special case.	(see get_rte_attribute_*)
 	 */
 	Node	   *funcexpr;		/* expression tree for func call */
 	List	   *funccoltypes;	/* OID list of column type OIDs */
 	List	   *funccoltypmods; /* integer list of column typmods */
 	List	   *funccolcollations;		/* OID list of column collation OIDs */
-	bool		funcordinality;	/* is this called WITH ORDINALITY? */
+	bool		funcordinality; /* is this called WITH ORDINALITY? */
 
 	/*
 	 * Fields valid for a values RTE (else NIL):
@@ -811,10 +828,10 @@ typedef struct RangeTblEntry
 typedef struct WithCheckOption
 {
 	NodeTag		type;
-	char	   *viewname;	/* name of view that specified the WCO */
-	Node	   *qual;		/* constraint qual to check */
-	bool		cascaded;	/* true = WITH CASCADED CHECK OPTION */
-} WithCheckOption;
+	char	   *viewname;		/* name of view that specified the WCO */
+	Node	   *qual;			/* constraint qual to check */
+	bool		cascaded;		/* true = WITH CASCADED CHECK OPTION */
+}	WithCheckOption;
 
 /*
  * SortGroupClause -
@@ -2371,7 +2388,7 @@ typedef enum ViewCheckOption
 	NO_CHECK_OPTION,
 	LOCAL_CHECK_OPTION,
 	CASCADED_CHECK_OPTION
-} ViewCheckOption;
+}	ViewCheckOption;
 
 typedef struct ViewStmt
 {
@@ -2381,7 +2398,7 @@ typedef struct ViewStmt
 	Node	   *query;			/* the SELECT query */
 	bool		replace;		/* replace an existing view? */
 	List	   *options;		/* options from WITH clause */
-	ViewCheckOption	withCheckOption; /* WITH CHECK OPTION */
+	ViewCheckOption withCheckOption;	/* WITH CHECK OPTION */
 } ViewStmt;
 
 /* ----------------------
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 8bd34d6..9196b41 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -180,6 +180,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -314,6 +315,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..bcd1719 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -41,11 +41,14 @@ typedef struct WindowObjectData *WindowObject;
 #define WindowObjectIsValid(winobj) \
 	((winobj) != NULL && IsA(winobj, WindowObjectData))
 
+extern MemoryContext WinGetPartitionMemoryContext(WindowObject winobj);
 extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int	WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 7b31d13..e5a248e 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
-                                    pg_get_viewdef                                     
----------------------------------------------------------------------------------------
-  SELECT i.i,                                                                         +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+                                     pg_get_viewdef                                      
+-----------------------------------------------------------------------------------------
+  SELECT i.i,                                                                           +
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER w AS lagged_by_2                                     +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1033,5 +1044,197 @@ FROM empsalary GROUP BY depname;
  25100 |          1 |        22600 | develop
 (3 rows)
 
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
+-- test non-deterministic lag (i.e. the lag-by value depends on the data)
+ALTER TABLE empsalary ADD an_offset INTEGER NOT NULL DEFAULT 1;
+SELECT term_date, lead(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6ee3696..2aac686 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -272,5 +281,53 @@ SELECT sum(salary), row_number() OVER (ORDER BY depname), sum(
     depname
 FROM empsalary GROUP BY depname;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- test non-deterministic lag (i.e. the lag-by value depends on the data)
+ALTER TABLE empsalary ADD an_offset INTEGER NOT NULL DEFAULT 1;
+
+SELECT term_date, lead(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 7dd1ef2..54ed0a4 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -12328,6 +12328,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12342,7 +12343,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12355,6 +12358,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -12369,7 +12373,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -12463,11 +12469,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 544ba98..23cd972 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -1981,7 +1981,6 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
  * API exposed to window functions
  ***********************************************************************/
 
-
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -2017,6 +2016,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ *		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a9812af..c59ab63 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -288,6 +288,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -547,7 +548,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -577,7 +578,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11572,19 +11573,28 @@ filter_clause:
              | /*EMPTY*/                            { $$ = NULL; }
          ;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls: 
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; } 
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{ 
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
-					n->location = @2;
+					n->location = @3;
 					$$ = n;
 				}
 			| /*EMPTY*/
@@ -12561,6 +12571,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12650,6 +12661,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 98cb58a..2bf0b00 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -579,28 +579,80 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			refwin = (WindowDef *) lfirst(lc);
 			winref++;
 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
-			{
-				wfunc->winref = winref;
 				break;
-			}
 		}
+
 		if (lc == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions == FRAMEOPTION_DEFAULTS)
+			wfunc->winref = winref;
+		else
+		{
+			/*
+			 * This is the window we want - but we have to tweak the
+			 * definition slightly (e.g. to support the IGNORE NULLS frame
+			 * option) as we're not using the default (i.e. parent) frame
+			 * options.
+			 *
+			 * We'll create a 'child' (using refname to inherit everything
+			 * from the parent) that just overrides the frame options
+			 * (assuming it doesn't already exist):
+			 */
+			WindowDef  *clone = makeNode(WindowDef);
+
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			/*
+			 * Add this new definition to the list. Note that there's a chance
+			 * a window with this definition already exists!
+			 */
+			winref = 0;
+			foreach(lc, pstate->p_windowdefs)
+			{
+				refwin = (WindowDef *) lfirst(lc);
+
+				winref++;
+				if (refwin->refname &&
+					strcmp(refwin->refname, clone->refname) == 0 &&
+					equal(refwin->partitionClause, clone->partitionClause) &&
+					equal(refwin->orderClause, clone->orderClause) &&
+					refwin->frameOptions == clone->frameOptions &&
+					equal(refwin->startOffset, clone->startOffset) &&
+					equal(refwin->endOffset, clone->endOffset))
+				{
+					/*
+					 * found a duplicate window specification, don't need
+					 * clone
+					 */
+					wfunc->winref = winref;
+					pfree(clone);
+					break;
+				}
+			}
+			if (lc == NULL)		/* didn't find it? */
+			{
+				pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+				wfunc->winref = list_length(pstate->p_windowdefs);
+			}
+		}
 	}
 	else
 	{
@@ -819,8 +871,8 @@ check_ungrouped_columns_walker(Node *node,
 	 * If we find an aggregate call of the original level, do not recurse into
 	 * its arguments or filter; ungrouped vars there are not an error. We can
 	 * also skip looking at aggregates of higher levels, since they could not
-	 * possibly contain Vars of concern to us (see transformAggregateCall).
-	 * We do need to look at aggregates of lower levels, however.
+	 * possibly contain Vars of concern to us (see transformAggregateCall). We
+	 * do need to look at aggregates of lower levels, however.
 	 */
 	if (IsA(node, Aggref) &&
 		(int) ((Aggref *) node)->agglevelsup >= context->sublevels_up)
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index 2bd24c8..7066046 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -391,13 +391,13 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 	 */
 	if (nargs > 0 && vatype == ANYOID && func_variadic)
 	{
-		Oid		va_arr_typid = actual_arg_types[nargs - 1];
+		Oid			va_arr_typid = actual_arg_types[nargs - 1];
 
 		if (!OidIsValid(get_element_type(va_arr_typid)))
 			ereport(ERROR,
 					(errcode(ERRCODE_DATATYPE_MISMATCH),
 					 errmsg("VARIADIC argument must be an array"),
-			  parser_errposition(pstate, exprLocation((Node *) llast(fargs)))));
+			parser_errposition(pstate, exprLocation((Node *) llast(fargs)))));
 	}
 
 	/* build the appropriate output structure */
@@ -522,6 +522,23 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 					 errmsg("FILTER is not implemented in non-aggregate window functions"),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/*
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+				|| (strcmp("lead", strVal(llast(funcname))) != 0 &&
+					strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+						 parser_errposition(pstate, location)));
+			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index 9a1d12e..78b0738 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4764,11 +4764,16 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int			initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -4850,7 +4855,20 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
-	appendStringInfoChar(buf, ')');
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags
+	 * relevant inside the window def's ()s, then we'll be left with
+	 * "(<refname>)". We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1;			/* the trailing ")" */
+	}
+	else
+		appendStringInfoChar(buf, ')');
 }
 
 /* ----------
@@ -7493,7 +7511,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7501,6 +7519,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index b7c42d3..280b96d 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,7 +13,9 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
+#include "utils/memutils.h"
 #include "windowapi.h"
 
 /*
@@ -24,6 +26,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;			/* the index of the lead / lagged value */
+}	leadlag_const_context;
+
+/*
+ * lead-lag process helpers
+ */
+#define ISNULL_INDEX(i) (2 * (i))
+#define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +294,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ *	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +305,24 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+
+	/**
+	 * A ** pointer as we keep a Bitmapset * in the partition context, and
+	 * WinGetPartitionLocalMemory returns a pointer to whatever's in the
+	 * context.
+	 */
+	Bitmapset **null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't mark
+	 * at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +336,245 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if (!forward)
+	{
+		offset = -offset;
+	}
+
+	if (ignore_nulls && !const_offset)
+	{
+		int64		scanning,
+					current = WinGetCurrentPosition(winobj);
+		bool		scanForward;
+
+		/*
+		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+		 * "run the query, and pretend the rows with nulls in them don't
+		 * exist". This means that we'll scan from the current row an 'offset'
+		 * number of non-null rows, and then return that one.
+		 *
+		 * As the offset isn't constant we need efficient random access to the
+		 * partition, as we'll check upto O(partition size) tuples for each
+		 * row we're calculating the window function value for.
+		 */
+
+		null_values = (Bitmapset **) WinGetPartitionLocalMemory(winobj, sizeof(Bitmapset *));
+
+		if (*null_values == NULL)
+		{
+			MemoryContext oldcxt;
+
+			/*
+			 * Accessing tuples is expensive, so we'll keep track of the ones
+			 * we've accessed (more specifically, if they're null or not).
+			 * We'll need one bit for whether the value is null and one bit
+			 * for whether we've checked that tuple or not. We'll keep these
+			 * two bits together (as opposed to having two separate bitmaps)
+			 * to improve cache locality.
+			 *
+			 * However, we'd lose the efficient gains if we keep having to
+			 * resize the Bitmapset (by setting higher and higher bits). We
+			 * know the maximum number of bits we'll ever need, so we'll use
+			 * bms_make_singleton to force our Bitmapset up to the required
+			 * size.
+			 */
+			int64		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+			oldcxt = MemoryContextSwitchTo(GetMemoryChunkContext(null_values));
+			*null_values = bms_make_singleton(bits_needed + 1);
+			MemoryContextSwitchTo(oldcxt);
+		}
+
+		/*
+		 * We use offset >= 0 instead of just forward as the offset might be
+		 * in the opposite direction to the way we're scanning. We'll then
+		 * force offset to be positive to make counting down the rows easier.
+		 */
+		scanForward = offset == 0 ? forward : (offset > 0);
+		offset = abs(offset);
+
+		for (scanning = current;; scanForward ? ++scanning : --scanning)
+		{
+			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+			{
+				isout = true;
+
+				/*
+				 * As we're out of the window we want to return NULL or the
+				 * default value, but not whatever's left in result. We'll use
+				 * the isnull flag to say "ignore it"!
+				 */
+				isnull = true;
+				result = (Datum) 0;
+
+				break;
+			}
+
+			if (bms_is_member(HAVESCANNED_INDEX(scanning), *null_values))
+			{
+				isnull = bms_is_member(ISNULL_INDEX(scanning), *null_values);
+			}
+			else
+			{
+				/*
+				 * first time we've accessed this index; let's see if it's
+				 * null:
+				 */
+				result = WinGetFuncArgInPartition(winobj, 0,
+												  scanning,
+												  WINDOW_SEEK_HEAD,
+												  false,
+												  &isnull, &isout);
+				if (isout)
+					break;
+
+				bms_add_member(*null_values, HAVESCANNED_INDEX(scanning));
+				if (isnull)
+				{
+					bms_add_member(*null_values, ISNULL_INDEX(scanning));
+				}
+			}
+
+			/*
+			 * Now the isnull flag is set correctly. If !isnull there's a
+			 * chance that we may stop iterating here:
+			 */
+			if (!isnull)
+			{
+				if (offset == 0)
+				{
+					result = WinGetFuncArgInPartition(winobj, 0,
+													  scanning,
+													  WINDOW_SEEK_HEAD,
+													  false,
+													  &isnull, &isout);
+					break;
+				}
+				else
+					--offset;	/* it's not null, so we're one step closer to
+								 * the value we want */
+			}
+			else if (scanning == current)
+			{
+				/*--------
+				 * A slight edge case. Consider:
+				 *
+				 * =================
+				 *	 A	 | lag(A, 1)
+				 * =================
+				 *	 1	 |	 NULL
+				 *	 2	 |	  1
+				 *	NULL |	  ?
+				 * =================
+				 *
+				 * Does a lag of one when the current value is null mean go back to the first
+				 * non-null value (i.e. 2), or find the previous non-null value of the first
+				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+				 * need to correct slightly:
+				 *--------
+				 */
+				--offset;
+			}
+		}
+	}
+	else if (ignore_nulls /* && const_offset */ )
+	{
+		/*
+		 * We can process a constant offset much more efficiently; initially
+		 * we'll scan through the first <offset> non-null rows, and store that
+		 * index. On subsequent rows we'll decide whether to push that index
+		 * forwards to the next non-null value, or just return it again.
+		 */
+		leadlag_const_context *context = WinGetPartitionLocalMemory(
+																	winobj,
+											  sizeof(leadlag_const_context));
+		int			count_forward = 0;
+
+		/*
+		 * Set the forward flag based on the direction of traversal - remember
+		 * we can have a LEAD or LAG of -1, and that should be equivalent to a
+		 * LAG or LEAD of 1 respectively.
+		 */
+		forward = offset == 0 ? forward : (offset > 0);
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
-									  &isnull, &isout);
+		if (WinGetCurrentPosition(winobj) == 0)
+			if (forward)
+				count_forward = offset;
+			else
+				context->next = offset; /* LAG, so offset is negative */
+		else
+		{
+			/*
+			 * LEADs and LAGs are actually pretty similar - the decision of
+			 * whether or not to push our offset value forwards depends on the
+			 * current row (for LEADs) or the previous row (for LAGs) is NULL
+			 * - hence the (forward ? 0 : -1) below.
+			 */
+			result = WinGetFuncArgInPartition(winobj, 0,
+											  forward ? 0 : -1,
+											  WINDOW_SEEK_CURRENT,
+											  forward,
+											  &isnull, &isout);
+			if (!isnull)
+				count_forward = 1;
+		}
+
+		/*
+		 * Count forward through the rows, skipping nulls and terminating if
+		 * we run off the end of the window.
+		 */
+		for (; count_forward > 0 && !isout; --count_forward)
+		{
+			do
+			{
+				/*
+				 * Conveniently, calling WinGetFuncArgInPartition with an
+				 * absolute index less than zero (correctly) sets isout and
+				 * isnull to true
+				 */
+				result = WinGetFuncArgInPartition(winobj, 0,
+												  ++(context->next),
+												  WINDOW_SEEK_HEAD,
+												  !forward,
+												  &isnull, &isout);
+			}
+			while (isnull && !isout);
+		}
+
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  context->next,
+										  WINDOW_SEEK_HEAD,
+										  !forward,
+										  &isnull, &isout);
+	}
+	else
+	{
+		/*
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/*
+			 * Don't return whatever's lying around in result, force the
+			 * output to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 51fef68..a26fc01 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -128,7 +128,7 @@ typedef struct Query
 
 	List	   *targetList;		/* target list (of TargetEntry) */
 
-	List	   *withCheckOptions; /* a list of WithCheckOption's */
+	List	   *withCheckOptions;		/* a list of WithCheckOption's */
 
 	List	   *returningList;	/* return-values list (of TargetEntry) */
 
@@ -406,19 +406,35 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. In this case, the per-field
+ * comments to determine what the semantics are:
+ *		VIRTUAL:
+ *			If NULL, then the parent's (refname) value is used.
+ *		MANDATORY:
+ *			Never inherited from the parent, so must be specified -
+ *			but can be NULL.
+ *		SUPER:
+ *			Always inherited from parent, any local version ignored.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* window's own name [MANDATORY value of NULL] */
+	char	   *name;
+	/* referenced window name, if any [MANDATORY] */
+	char	   *refname;
+	/* PARTITION BY expression list [VIRTUAL] */
+	List	   *partitionClause;
+	/* ORDER BY (list of SortBy) [SUPER] */
+	List	   *orderClause;
+	/* frame_clause options, see below	[MANDATORY] */
+	int			frameOptions;
+	/* expression for starting bound, if any [MANDATORY] */
+	Node	   *startOffset;
+	/* expression for ending bound, if any [MANDATORY] */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown [MANDATORY] */
+	int			location;
 } WindowDef;
 
 /*
@@ -443,6 +459,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
@@ -655,10 +672,10 @@ typedef struct XmlSerialize
  *
  *	  The same comments apply to FUNCTION RTEs when the function's return type
  *	  is a named composite type. In addition, for all return types, FUNCTION
- *    RTEs with ORDINALITY must always have the last colname entry being the
- *    one for the ordinal column; this is enforced when constructing the RTE.
- *    Thus when ORDINALITY is used, there will be exactly one more colname
- *    than would have been present otherwise.
+ *	  RTEs with ORDINALITY must always have the last colname entry being the
+ *	  one for the ordinal column; this is enforced when constructing the RTE.
+ *	  Thus when ORDINALITY is used, there will be exactly one more colname
+ *	  than would have been present otherwise.
  *
  *	  In JOIN RTEs, the colnames in both alias and eref are one-to-one with
  *	  joinaliasvars entries.  A JOIN RTE will omit columns of its inputs when
@@ -760,18 +777,18 @@ typedef struct RangeTblEntry
 	 * If the function returns an otherwise-unspecified RECORD, funccoltypes
 	 * lists the column types declared in the RTE's column type specification,
 	 * funccoltypmods lists their declared typmods, funccolcollations their
-	 * collations.  Note that in this case, ORDINALITY is not permitted, so
+	 * collations.	Note that in this case, ORDINALITY is not permitted, so
 	 * there is no extra ordinal column to be allowed for.
 	 *
-     * Otherwise, those fields are NIL, and the result column types must be
+	 * Otherwise, those fields are NIL, and the result column types must be
 	 * derived from the funcexpr while treating the ordinal column, if
-	 * present, as a special case.  (see get_rte_attribute_*)
+	 * present, as a special case.	(see get_rte_attribute_*)
 	 */
 	Node	   *funcexpr;		/* expression tree for func call */
 	List	   *funccoltypes;	/* OID list of column type OIDs */
 	List	   *funccoltypmods; /* integer list of column typmods */
 	List	   *funccolcollations;		/* OID list of column collation OIDs */
-	bool		funcordinality;	/* is this called WITH ORDINALITY? */
+	bool		funcordinality; /* is this called WITH ORDINALITY? */
 
 	/*
 	 * Fields valid for a values RTE (else NIL):
@@ -811,10 +828,10 @@ typedef struct RangeTblEntry
 typedef struct WithCheckOption
 {
 	NodeTag		type;
-	char	   *viewname;	/* name of view that specified the WCO */
-	Node	   *qual;		/* constraint qual to check */
-	bool		cascaded;	/* true = WITH CASCADED CHECK OPTION */
-} WithCheckOption;
+	char	   *viewname;		/* name of view that specified the WCO */
+	Node	   *qual;			/* constraint qual to check */
+	bool		cascaded;		/* true = WITH CASCADED CHECK OPTION */
+}	WithCheckOption;
 
 /*
  * SortGroupClause -
@@ -2371,7 +2388,7 @@ typedef enum ViewCheckOption
 	NO_CHECK_OPTION,
 	LOCAL_CHECK_OPTION,
 	CASCADED_CHECK_OPTION
-} ViewCheckOption;
+}	ViewCheckOption;
 
 typedef struct ViewStmt
 {
@@ -2381,7 +2398,7 @@ typedef struct ViewStmt
 	Node	   *query;			/* the SELECT query */
 	bool		replace;		/* replace an existing view? */
 	List	   *options;		/* options from WITH clause */
-	ViewCheckOption	withCheckOption; /* WITH CHECK OPTION */
+	ViewCheckOption withCheckOption;	/* WITH CHECK OPTION */
 } ViewStmt;
 
 /* ----------------------
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 8bd34d6..9196b41 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -180,6 +180,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -314,6 +315,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 5bbf1fa..c6b179c 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int	WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index 7b31d13..e5a248e 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -5,19 +5,21 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
   depname  | empno | salary |  sum  
 -----------+-------+--------+-------
@@ -931,30 +933,39 @@ FROM tenk1 WHERE unique1 < 10;
   17 |       9
 (10 rows)
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
 SELECT * FROM v_window;
- i  | sum_rows 
-----+----------
-  1 |        3
-  2 |        6
-  3 |        9
-  4 |       12
-  5 |       15
-  6 |       18
-  7 |       21
-  8 |       24
-  9 |       27
- 10 |       19
+ i  | sum_rows | lagged_by_1 | lagged_by_2 
+----+----------+-------------+-------------
+ 10 |       19 |             |           8
+  9 |       27 |          10 |           7
+  8 |       24 |           9 |           6
+  7 |       21 |           8 |           5
+  6 |       18 |           7 |           4
+  5 |       15 |           6 |           3
+  4 |       12 |           5 |           2
+  3 |        9 |           4 |           1
+  2 |        6 |           3 |            
+  1 |        3 |           2 |            
 (10 rows)
 
 SELECT pg_get_viewdef('v_window');
-                                    pg_get_viewdef                                     
----------------------------------------------------------------------------------------
-  SELECT i.i,                                                                         +
-     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows+
-    FROM generate_series(1, 10) i(i);
+                                     pg_get_viewdef                                      
+-----------------------------------------------------------------------------------------
+  SELECT i.i,                                                                           +
+     sum(i.i) OVER (ORDER BY i.i ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows, +
+     lag(i.i, 1) IGNORE NULLS OVER (ORDER BY i.i DESC) AS lagged_by_1,                  +
+     lag(i.i, 2) IGNORE NULLS OVER w AS lagged_by_2                                     +
+    FROM generate_series(1, 10) i(i)                                                    +
+   WINDOW w AS (ORDER BY i.i);
 (1 row)
 
 -- with UNION
@@ -1033,5 +1044,197 @@ FROM empsalary GROUP BY depname;
  25100 |          1 |        22600 | develop
 (3 rows)
 
+-- test null behaviour: (1) lags
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 
+ 11-17-2009 | 
+            | 11-17-2009
+            | 
+            | 
+(10 rows)
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ respect |   lag   
+---------+---------
+ frog    | 
+         | frog
+         | frog
+ chicken | frog
+         | chicken
+         | chicken
+ tiger   | chicken
+ gorilla | tiger
+         | gorilla
+         | gorilla
+(10 rows)
+
+-- (2) leads
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 
+            | 
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, first_value(term_date) IGNORE NULLS OVER (...
+                          ^
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY...
+                          ^
+-- test non-deterministic lag (i.e. the lag-by value depends on the data)
+ALTER TABLE empsalary ADD an_offset INTEGER NOT NULL DEFAULT 1;
+SELECT term_date, lead(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lead    
+------------+------------
+            | 03-05-2009
+            | 03-05-2009
+ 03-05-2009 | 09-22-2010
+ 09-22-2010 | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+ 11-17-2009 | 
+            | 
+            | 
+            | 
+(10 rows)
+
+SELECT term_date, lag(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+ term_date  |    lag     
+------------+------------
+            | 
+            | 
+ 03-05-2009 | 
+ 09-22-2010 | 03-05-2009
+            | 09-22-2010
+            | 09-22-2010
+ 11-17-2009 | 09-22-2010
+            | 11-17-2009
+            | 11-17-2009
+            | 11-17-2009
+(10 rows)
+
 -- cleanup
 DROP TABLE empsalary;
+-- some more test cases:
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+ val | lead 
+-----+------
+   1 |    3
+   2 |    4
+   3 |    5
+   4 |    6
+     |    6
+     |    6
+     |    6
+   5 |    7
+   6 |     
+   7 |     
+(10 rows)
+
+DROP TABLE test_table;
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();
+ val | ignore | respect 
+-----+--------+---------
+   1 |      3 |       3
+   2 |      4 |       4
+   3 |      5 |        
+   4 |      6 |        
+     |      6 |        
+     |      6 |       5
+     |      6 |       6
+   5 |      7 |       7
+   6 |        |        
+   7 |        |        
+(10 rows)
+
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 6ee3696..2aac686 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -6,20 +6,22 @@ CREATE TEMPORARY TABLE empsalary (
     depname varchar,
     empno bigint,
     salary int,
-    enroll_date date
+    enroll_date date,
+    term_date date,
+    respect text
 );
 
 INSERT INTO empsalary VALUES
-('develop', 10, 5200, '2007-08-01'),
-('sales', 1, 5000, '2006-10-01'),
-('personnel', 5, 3500, '2007-12-10'),
-('sales', 4, 4800, '2007-08-08'),
-('personnel', 2, 3900, '2006-12-23'),
-('develop', 7, 4200, '2008-01-01'),
-('develop', 9, 4500, '2008-01-01'),
-('sales', 3, 4800, '2007-08-01'),
-('develop', 8, 6000, '2006-10-01'),
-('develop', 11, 5200, '2007-08-15');
+('develop', 10, 5200, '2007-08-01', null, null),
+('sales', 1, 5000, '2006-10-01', null, 'frog'),
+('personnel', 5, 3500, '2007-12-10', null, null),
+('sales', 4, 4800, '2007-08-08', '2010-09-22', 'chicken'),
+('personnel', 2, 3900, '2006-12-23', null, null),
+('develop', 7, 4200, '2008-01-01', null, null),
+('develop', 9, 4500, '2008-01-01', null, 'gorilla'),
+('sales', 3, 4800, '2007-08-01', '2009-03-05', null),
+('develop', 8, 6000, '2006-10-01', '2009-11-17', 'tiger'),
+('develop', 11, 5200, '2007-08-15', null, null);
 
 SELECT depname, empno, salary, sum(salary) OVER (PARTITION BY depname) FROM empsalary ORDER BY depname, salary;
 
@@ -222,9 +224,16 @@ SELECT sum(unique1) over
 	unique1
 FROM tenk1 WHERE unique1 < 10;
 
+-- test view definitions are preserved
 CREATE TEMP VIEW v_window AS
-	SELECT i, sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows
-	FROM generate_series(1, 10) i;
+	SELECT
+		i,
+		sum(i) over (order by i rows between 1 preceding and 1 following) as sum_rows,
+		lag(i, 1) IGNORE NULLS OVER (ORDER BY i DESC) AS lagged_by_1,
+		lag(i, 2) IGNORE NULLS OVER w AS lagged_by_2
+	FROM generate_series(1, 10) i
+	WINDOW w as (ORDER BY i ASC);
+
 
 SELECT * FROM v_window;
 
@@ -272,5 +281,53 @@ SELECT sum(salary), row_number() OVER (ORDER BY depname), sum(
     depname
 FROM empsalary GROUP BY depname;
 
+-- test null behaviour: (1) lags
+
+SELECT term_date, lag(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a numeric (date) column
+SELECT term_date, lag(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- a text column
+SELECT respect, lag(respect) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- (2) leads
+
+SELECT term_date, lead(term_date) OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) RESPECT NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lead(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT term_date, first_value(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+SELECT term_date, max(term_date) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+-- test non-deterministic lag (i.e. the lag-by value depends on the data)
+ALTER TABLE empsalary ADD an_offset INTEGER NOT NULL DEFAULT 1;
+
+SELECT term_date, lead(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
+SELECT term_date, lag(term_date, an_offset) IGNORE NULLS OVER (ORDER BY empno) FROM empsalary ORDER BY empno;
+
 -- cleanup
 DROP TABLE empsalary;
+
+-- some more test cases:
+
+-- (1) leading with an order-by
+CREATE TABLE test_table (
+       id serial,
+       val integer);
+INSERT INTO test_table (val) SELECT * FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]);
+SELECT val, lead(val, 2) IGNORE NULLS OVER (ORDER BY id) FROM test_table ORDER BY id;
+DROP TABLE test_table;
+
+-- (2) two functions in the same window
+SELECT val,
+	lead(val, 2) IGNORE NULLS OVER w AS ignore,
+	lead(val, 2) RESPECT NULLS OVER w AS respect
+FROM unnest(ARRAY[1,2,3,4,NULL, NULL, NULL, 5, 6, 7]) AS val
+WINDOW w as ();

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 0809a6d..5da852e 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -13185,6 +13185,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lag(<replaceable class="parameter">value</replaceable> <type>any</>
              [, <replaceable class="parameter">offset</replaceable> <type>integer</>
              [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -13199,7 +13200,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -13212,6 +13215,7 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
          lead(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+         [ { RESPECT | IGNORE } NULLS ]
        </function>
       </entry>
       <entry>
@@ -13226,7 +13230,9 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
        <replaceable class="parameter">default</replaceable> are evaluated
        with respect to the current row.  If omitted,
        <replaceable class="parameter">offset</replaceable> defaults to 1 and
-       <replaceable class="parameter">default</replaceable> to null
+       <replaceable class="parameter">default</replaceable> to null. If
+       <literal>IGNORE NULLS</> is specified then the function will be evaluated
+       as if the rows containing nulls didn't exist.
       </entry>
      </row>
 
@@ -13320,11 +13326,10 @@ SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
   <note>
    <para>
     The SQL standard defines a <literal>RESPECT NULLS</> or
-    <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
-    <function>first_value</>, <function>last_value</>, and
-    <function>nth_value</>.  This is not implemented in
-    <productname>PostgreSQL</productname>: the behavior is always the
-    same as the standard's default, namely <literal>RESPECT NULLS</>.
+    <literal>IGNORE NULLS</> option for <function>first_value</>,
+    <function>last_value</>, and <function>nth_value</>.  This is not
+    implemented in <productname>PostgreSQL</productname>: the behavior is
+    always the same as the standard's default, namely <literal>RESPECT NULLS</>.
     Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
     option for <function>nth_value</> is not implemented: only the
     default <literal>FROM FIRST</> behavior is supported.  (You can achieve
diff --git a/src/backend/executor/nodeWindowAgg.c b/src/backend/executor/nodeWindowAgg.c
index 2fcc630..5cea825 100644
--- a/src/backend/executor/nodeWindowAgg.c
+++ b/src/backend/executor/nodeWindowAgg.c
@@ -2431,7 +2431,6 @@ window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
  * API exposed to window functions
  ***********************************************************************/
 
-
 /*
  * WinGetPartitionLocalMemory
  *		Get working memory that lives till end of partition processing
@@ -2467,6 +2466,17 @@ WinGetCurrentPosition(WindowObject winobj)
 }
 
 /*
+ * WinGetFrameOptions
+ *		Returns the frame option flags
+ */
+int
+WinGetFrameOptions(WindowObject winobj)
+{
+	Assert(WindowObjectIsValid(winobj));
+	return winobj->winstate->frameOptions;
+}
+
+/*
  * WinGetPartitionRowCount
  *		Return total number of rows contained in the current partition.
  *
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7b9895d..f11bc66 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -290,6 +290,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <list>	TriggerEvents TriggerOneEvent
 %type <value>	TriggerFuncArg
 %type <node>	TriggerWhen
+%type <ival>	opt_ignore_nulls
 
 %type <list>	event_trigger_when_list event_trigger_value_list
 %type <defelt>	event_trigger_when_item
@@ -552,7 +553,7 @@ 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 IN_P
+	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
 	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
@@ -582,7 +583,7 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
 	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
 	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
-	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
+	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
 	ROW ROWS RULE
 
 	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
@@ -11885,19 +11886,28 @@ window_definition:
 				}
 		;
 
-over_clause: OVER window_specification
-				{ $$ = $2; }
-			| OVER ColId
+opt_ignore_nulls:
+			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
+			| RESPECT NULLS_P					{ $$ = 0; }
+			| /* EMPTY */						{ $$ = 0; }
+		;
+
+over_clause: opt_ignore_nulls OVER window_specification
+				{
+					$3->frameOptions |= $1;
+					$$ = $3;
+				}
+			| opt_ignore_nulls OVER ColId
 				{
 					WindowDef *n = makeNode(WindowDef);
-					n->name = $2;
+					n->name = $3;
 					n->refname = NULL;
 					n->partitionClause = NIL;
 					n->orderClause = NIL;
-					n->frameOptions = FRAMEOPTION_DEFAULTS;
+					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
 					n->startOffset = NULL;
 					n->endOffset = NULL;
-					n->location = @2;
+					n->location = @3;
 					$$ = n;
 				}
 			| /*EMPTY*/
@@ -12891,6 +12901,7 @@ unreserved_keyword:
 			| HOUR_P
 			| IDENTITY_P
 			| IF_P
+			| IGNORE
 			| IMMEDIATE
 			| IMMUTABLE
 			| IMPLICIT_P
@@ -12980,6 +12991,7 @@ unreserved_keyword:
 			| REPLACE
 			| REPLICA
 			| RESET
+			| RESPECT
 			| RESTART
 			| RESTRICT
 			| RETURNS
diff --git a/src/backend/parser/parse_agg.c b/src/backend/parser/parse_agg.c
index 272d27f..6edfc4d 100644
--- a/src/backend/parser/parse_agg.c
+++ b/src/backend/parser/parse_agg.c
@@ -694,28 +694,82 @@ transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
 	{
 		Index		winref = 0;
 		ListCell   *lc;
+		WindowDef  *refwin = NULL;
 
 		Assert(windef->refname == NULL &&
 			   windef->partitionClause == NIL &&
-			   windef->orderClause == NIL &&
-			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
+			   windef->orderClause == NIL);
 
 		foreach(lc, pstate->p_windowdefs)
 		{
-			WindowDef  *refwin = (WindowDef *) lfirst(lc);
-
+			WindowDef *thiswin = (WindowDef *) lfirst(lc);
 			winref++;
-			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
+
+			if (thiswin->name && strcmp(thiswin->name, windef->name) == 0)
+			{
+				/*
+				 * "thiswin" is the window we want - but we have to tweak the
+				 * definition slightly as some window options (e.g. IGNORE
+				 * NULLS) can't be specified a standalone window definition;
+				 * they can only be specified when invoking a window function
+				 * over a window definition. However, we don't want to modify
+				 * the window def itself (as that'll affect other window
+				 * functions that use it - so if we need to make changes to it
+				 * we'll clone refwin, change the clone and add the clone to
+				 * the list of window definitions in pstate.
+				 *
+				 * There's one catch: what if a statement has two (or more)
+				 * window function calls that reference the same window
+				 * definition, and both have IGNORE NULLs? We don't want to
+				 * add two modified definitions to pstate, so we'll only break
+				 * if thiswin is an exact match - if not we'll keep looking for
+				 * a window definition with the same name *and* same frame
+				 * options.
+				 */
+				wfunc->winref = winref;
+				refwin = thiswin;
+				if(windef->frameOptions == FRAMEOPTION_DEFAULTS)
+					break; /* don't need to clone, so just use this one */
+			}
+
+			if (refwin && /* we need to have found the parent window */
+				thiswin->refname &&
+				strcmp(thiswin->refname, windef->name) == 0 && /* it reference the right parent */
+				thiswin->frameOptions == windef->frameOptions)
 			{
+				/* found a clone window specification that we can re-use */
 				wfunc->winref = winref;
+				refwin = thiswin;
 				break;
 			}
 		}
-		if (lc == NULL)			/* didn't find it? */
+
+		if (refwin == NULL)			/* didn't find it? */
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_OBJECT),
 					 errmsg("window \"%s\" does not exist", windef->name),
 					 parser_errposition(pstate, windef->location)));
+		else if (windef->frameOptions != refwin->frameOptions /* we can't use the clone */
+			&& windef->frameOptions != FRAMEOPTION_DEFAULTS) /* we can't use the parent */
+		{
+			/*
+			 * This means we've found the parent, but no clones (if there were
+			 * any) had the correct frame options. We'll clone the parent we
+			 * found (refwin), set the frame options we want and add the new
+			 * clone to pstate:
+			 */
+			WindowDef *clone = makeNode(WindowDef);
+
+			clone->name = NULL;
+			clone->refname = pstrdup(refwin->name);
+			clone->frameOptions = windef->frameOptions; /* Note windef! */
+			clone->startOffset = copyObject(refwin->startOffset);
+			clone->endOffset = copyObject(refwin->endOffset);
+			clone->location = refwin->location;
+
+			pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+			wfunc->winref = list_length(pstate->p_windowdefs);
+		}
 	}
 	else
 	{
diff --git a/src/backend/parser/parse_func.c b/src/backend/parser/parse_func.c
index cc46084..ce39955 100644
--- a/src/backend/parser/parse_func.c
+++ b/src/backend/parser/parse_func.c
@@ -726,6 +726,22 @@ ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
 							NameListToString(funcname)),
 					 parser_errposition(pstate, location)));
 
+		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+		{
+			/*
+			 * As this is only implemented for the lead & lag window functions
+			 * we'll filter out all aggregate functions too.
+			 */
+			if (fdresult != FUNCDETAIL_WINDOWFUNC
+				|| (strcmp("lead", strVal(llast(funcname))) != 0 &&
+					strcmp("lag", strVal(llast(funcname))) != 0))
+			{
+				ereport(ERROR,
+						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+						 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+						 parser_errposition(pstate, location)));			}
+		}
+
 		/*
 		 * ordered aggs not allowed in windows yet
 		 */
diff --git a/src/backend/utils/adt/ruleutils.c b/src/backend/utils/adt/ruleutils.c
index ea7b8c5..add4048 100644
--- a/src/backend/utils/adt/ruleutils.c
+++ b/src/backend/utils/adt/ruleutils.c
@@ -4916,11 +4916,16 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 	bool		needspace = false;
 	const char *sep;
 	ListCell   *l;
+	size_t		refname_len = 0;
+	int			initial_buf_len = buf->len;
 
 	appendStringInfoChar(buf, '(');
 	if (wc->refname)
 	{
-		appendStringInfoString(buf, quote_identifier(wc->refname));
+		const char *quoted_refname = quote_identifier(wc->refname);
+
+		refname_len = strlen(quoted_refname);
+		appendStringInfoString(buf, quoted_refname);
 		needspace = true;
 	}
 	/* partition clauses are always inherited, so only print if no refname */
@@ -5002,7 +5007,20 @@ get_rule_windowspec(WindowClause *wc, List *targetList,
 		/* we will now have a trailing space; remove it */
 		buf->len--;
 	}
-	appendStringInfoChar(buf, ')');
+
+	/*
+	 * We'll tidy up the output slightly; if we've got a refname, but haven't
+	 * overridden the partition-by, order-by or any of the frame flags
+	 * relevant inside the window def's ()s, then we'll be left with
+	 * "(<refname>)". We'll trim off the brackets in this case:
+	 */
+	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
+	{
+		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
+		buf->len -= 1;			/* the trailing ")" */
+	}
+	else
+		appendStringInfoChar(buf, ')');
 }
 
 /* ----------
@@ -7674,7 +7692,7 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 		get_rule_expr((Node *) wfunc->aggfilter, context, false);
 	}
 
-	appendStringInfoString(buf, ") OVER ");
+	appendStringInfoString(buf, ") ");
 
 	foreach(l, context->windowClause)
 	{
@@ -7682,6 +7700,10 @@ get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
 
 		if (wc->winref == wfunc->winref)
 		{
+			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+				appendStringInfoString(buf, "IGNORE NULLS ");
+			appendStringInfoString(buf, "OVER ");
+
 			if (wc->name)
 				appendStringInfoString(buf, quote_identifier(wc->name));
 			else
diff --git a/src/backend/utils/adt/windowfuncs.c b/src/backend/utils/adt/windowfuncs.c
index 19f1fde..ccb53ce 100644
--- a/src/backend/utils/adt/windowfuncs.c
+++ b/src/backend/utils/adt/windowfuncs.c
@@ -13,7 +13,9 @@
  */
 #include "postgres.h"
 
+#include "nodes/bitmapset.h"
 #include "utils/builtins.h"
+#include "utils/memutils.h"
 #include "windowapi.h"
 
 /*
@@ -24,6 +26,18 @@ typedef struct rank_context
 	int64		rank;			/* current rank */
 } rank_context;
 
+
+typedef struct leadlag_const_context
+{
+	int64		next;			/* the index of the lead / lagged value */
+}	leadlag_const_context;
+
+/*
+ * lead-lag process helpers
+ */
+#define ISNULL_INDEX(i) (2 * (i))
+#define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+
 /*
  * ntile process information
  */
@@ -280,7 +294,8 @@ window_ntile(PG_FUNCTION_ARGS)
  * common operation of lead() and lag()
  * For lead() forward is true, whereas for lag() it is false.
  * withoffset indicates we have an offset second argument.
- * withdefault indicates we have a default third argument.
+ * withdefault indicates we have a default third argument. We'll only
+ *	return this default if the offset we want is outside of the partition.
  */
 static Datum
 leadlag_common(FunctionCallInfo fcinfo,
@@ -290,8 +305,24 @@ leadlag_common(FunctionCallInfo fcinfo,
 	int32		offset;
 	bool		const_offset;
 	Datum		result;
-	bool		isnull;
-	bool		isout;
+	bool		isnull = false;
+	bool		isout = false;
+	bool		ignore_nulls;
+
+	/**
+	 * A ** pointer as we keep a Bitmapset * in the partition context, and
+	 * WinGetPartitionLocalMemory returns a pointer to whatever's in the
+	 * context.
+	 */
+	Bitmapset **null_values;
+
+	/*
+	 * We want to set the markpos (the earliest tuple we can access) as
+	 * aggressively as possible to save memory, but if the offset isn't
+	 * constant we really need random access on the partition (so can't mark
+	 * at all).
+	 */
+	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
 
 	if (withoffset)
 	{
@@ -305,21 +336,247 @@ leadlag_common(FunctionCallInfo fcinfo,
 		offset = 1;
 		const_offset = true;
 	}
+	if (!forward)
+	{
+		offset = -offset;
+	}
 
-	result = WinGetFuncArgInPartition(winobj, 0,
-									  (forward ? offset : -offset),
-									  WINDOW_SEEK_CURRENT,
-									  const_offset,
-									  &isnull, &isout);
+	if (ignore_nulls)
+	{
+		if(const_offset)
+		{		int count_forward = 0;
+			leadlag_const_context *context;
+
+			/*
+			 * We can process a constant offset much more efficiently; initially
+			 * we'll scan through the first <offset> non-null rows, and store that
+			 * index. On subsequent rows we'll decide whether to push that index
+			 * forwards to the next non-null value, or just return it again.
+			 */
+			context = WinGetPartitionLocalMemory(winobj, sizeof(leadlag_const_context));
+
+			/*
+			 * Set the forward flag based on the direction of traversal - remember
+			 * we can have a LEAD or LAG of -1, and that should be equivalent to a
+			 * LAG or LEAD of 1 respectively.
+			 */
+			forward = offset == 0 ? forward : (offset > 0);
+
+			if (WinGetCurrentPosition(winobj) == 0)
+				if (forward)
+					count_forward = offset;
+				else
+					context->next = offset; /* LAG, so offset is negative */
+			else
+			{
+				/*
+				 * LEADs and LAGs are actually pretty similar - the decision of
+				 * whether or not to push our offset value forwards depends on the
+				 * current row (for LEADs) or the previous row (for LAGs) is NULL
+				 * - hence the (forward ? 0 : -1) below.
+				 */
+				result = WinGetFuncArgInPartition(winobj, 0,
+												  forward ? 0 : -1,
+												  WINDOW_SEEK_CURRENT,
+												  forward,
+												  &isnull, &isout);
+				if (!isnull)
+					count_forward = 1;
+			}
+
+			/*
+			 * Count forward through the rows, skipping nulls and terminating if
+			 * we run off the end of the window.
+			 */
+			for (; count_forward > 0 && !isout; --count_forward)
+			{
+				do
+				{
+					/*
+					 * Conveniently, calling WinGetFuncArgInPartition with an
+					 * absolute index less than zero (correctly) sets isout and
+					 * isnull to true
+					 */
+					result = WinGetFuncArgInPartition(winobj, 0,
+													  ++(context->next),
+													  WINDOW_SEEK_HEAD,
+													  !forward,
+													  &isnull, &isout);
+				}
+				while (isnull && !isout);
+			}
+
+			result = WinGetFuncArgInPartition(winobj, 0,
+											  context->next,
+											  WINDOW_SEEK_HEAD,
+											  !forward,
+											  &isnull, &isout);
+		}
+		else
+		{
+			int64		scanning,
+						current = WinGetCurrentPosition(winobj);
+			bool		scanForward;
+
+			/*
+			 * This case is a little complicated; we're defining "IGNORE NULLS" as
+			 * "run the query, and pretend the rows with nulls in them don't
+			 * exist". This means that we'll scan from the current row an 'offset'
+			 * number of non-null rows, and then return that one.
+			 *
+			 * As the offset isn't constant we need efficient random access to the
+			 * partition, as we'll check upto O(partition size) tuples for each
+			 * row we're calculating the window function value for.
+			 */
+
+			null_values = (Bitmapset **) WinGetPartitionLocalMemory(winobj, sizeof(Bitmapset *));
+
+			if (*null_values == NULL)
+			{
+				MemoryContext oldcxt;
+
+				/*
+				 * Accessing tuples is expensive, so we'll keep track of the ones
+				 * we've accessed (more specifically, if they're null or not).
+				 * We'll need one bit for whether the value is null and one bit
+				 * for whether we've checked that tuple or not. We'll keep these
+				 * two bits together (as opposed to having two separate bitmaps)
+				 * to improve cache locality.
+				 *
+				 * However, we'd lose the efficient gains if we keep having to
+				 * resize the Bitmapset (by setting higher and higher bits). We
+				 * know the maximum number of bits we'll ever need, so we'll use
+				 * bms_make_singleton to force our Bitmapset up to the required
+				 * size.
+				 */
+				int64		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+
+				oldcxt = MemoryContextSwitchTo(GetMemoryChunkContext(null_values));
+				*null_values = bms_make_singleton(bits_needed + 1);
+				MemoryContextSwitchTo(oldcxt);
+			}
+
+			/*
+			 * We use offset >= 0 instead of just forward as the offset might be
+			 * in the opposite direction to the way we're scanning. We'll then
+			 * force offset to be positive to make counting down the rows easier.
+			 */
+			scanForward = offset == 0 ? forward : (offset > 0);
+			offset = abs(offset);
+
+			for (scanning = current;; scanForward ? ++scanning : --scanning)
+			{
+				if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+				{
+					isout = true;
+
+					/*
+					 * As we're out of the window we want to return NULL or the
+					 * default value, but not whatever's left in result. We'll use
+					 * the isnull flag to say "ignore it"!
+					 */
+					isnull = true;
+					result = (Datum) 0;
+
+					break;
+				}
+
+				if (bms_is_member(HAVESCANNED_INDEX(scanning), *null_values))
+				{
+					isnull = bms_is_member(ISNULL_INDEX(scanning), *null_values);
+				}
+				else
+				{
+					/*
+					 * first time we've accessed this index; let's see if it's
+					 * null:
+					 */
+					result = WinGetFuncArgInPartition(winobj, 0,
+													  scanning,
+													  WINDOW_SEEK_HEAD,
+													  false,
+													  &isnull, &isout);
+					if (isout)
+						break;
+
+					bms_add_member(*null_values, HAVESCANNED_INDEX(scanning));
+					if (isnull)
+					{
+						bms_add_member(*null_values, ISNULL_INDEX(scanning));
+					}
+				}
+
+				/*
+				 * Now the isnull flag is set correctly. If !isnull there's a
+				 * chance that we may stop iterating here:
+				 */
+				if (!isnull)
+				{
+					if (offset == 0)
+					{
+						result = WinGetFuncArgInPartition(winobj, 0,
+														  scanning,
+														  WINDOW_SEEK_HEAD,
+														  false,
+														  &isnull, &isout);
+						break;
+					}
+					else
+						--offset;	/* it's not null, so we're one step closer to
+									 * the value we want */
+				}
+				else if (scanning == current)
+				{
+					/*--------
+					 * A slight edge case. Consider:
+					 *
+					 * =================
+					 *	 A	 | lag(A, 1)
+					 * =================
+					 *	 1	 |	 NULL
+					 *	 2	 |	  1
+					 *	NULL |	  ?
+					 * =================
+					 *
+					 * Does a lag of one when the current value is null mean go back to the first
+					 * non-null value (i.e. 2), or find the previous non-null value of the first
+					 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+					 * need to correct slightly:
+					 *--------
+					 */
+					--offset;
+				}
+			}
+		}
+	}
+	else
+	{
+		/*
+		 * We don't care about nulls; just get the row at the required offset.
+		 */
+		result = WinGetFuncArgInPartition(winobj, 0,
+										  offset,
+										  WINDOW_SEEK_CURRENT,
+										  const_offset,
+										  &isnull, &isout);
+	}
 
 	if (isout)
 	{
 		/*
-		 * target row is out of the partition; supply default value if
-		 * provided.  otherwise it'll stay NULL
+		 * Target row is out of the partition; supply default value if
+		 * provided.
 		 */
 		if (withdefault)
 			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+		else
+		{
+			/*
+			 * Don't return whatever's lying around in result, force the
+			 * output to null if there's no default.
+			 */
+			Assert(isnull);
+		}
 	}
 
 	if (isnull)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 18d4991..8b18db4 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -406,19 +406,38 @@ typedef struct SortBy
  * For entries in a WINDOW list, "name" is the window name being defined.
  * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
  * for the "OVER (window)" syntax, which is subtly different --- the latter
- * implies overriding the window frame clause.
+ * implies overriding the window frame clause. The semantics of each override
+ * depends on the field.
  */
 typedef struct WindowDef
 {
 	NodeTag		type;
-	char	   *name;			/* window's own name */
-	char	   *refname;		/* referenced window name, if any */
-	List	   *partitionClause;	/* PARTITION BY expression list */
-	List	   *orderClause;	/* ORDER BY (list of SortBy) */
-	int			frameOptions;	/* frame_clause options, see below */
-	Node	   *startOffset;	/* expression for starting bound, if any */
-	Node	   *endOffset;		/* expression for ending bound, if any */
-	int			location;		/* parse location, or -1 if none/unknown */
+	/* Window's own name. This must be NULL for overrides. */
+	char	   *name;
+	/* Referenced window name, if any. This must be present on overrides. */
+	char	   *refname;
+	/*
+	 * PARTITION BY expression list. If an override leaves this NULL, the
+	 * parent's partitionClause will be used.
+	 */
+	List	   *partitionClause;
+	/*
+	 * ORDER BY (list of SortBy). This field is ignored in overrides - the
+	 * parent's value will always be used.
+	 */
+	List	   *orderClause;
+	/*
+	 * The remaining fields in this struct must be specified on overrides,
+	 * even if the override's value is the same as the parent's.
+	 */
+	/* frame_clause options, see below */
+	int			frameOptions;
+	/* Expression for starting bound, if any */
+	Node	   *startOffset;
+	/* expression for ending bound, if any */
+	Node	   *endOffset;
+	/* parse location, or -1 if none/unknown */
+	int			location;
 } WindowDef;
 
 /*
@@ -443,6 +462,7 @@ typedef struct WindowDef
 #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
 #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
 #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+#define FRAMEOPTION_IGNORE_NULLS				0x04000
 
 #define FRAMEOPTION_START_VALUE \
 	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
diff --git a/src/include/parser/kwlist.h b/src/include/parser/kwlist.h
index 61fae22..c11c65a 100644
--- a/src/include/parser/kwlist.h
+++ b/src/include/parser/kwlist.h
@@ -180,6 +180,7 @@ 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, UNRESERVED_KEYWORD)
 PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
 PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
 PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
@@ -314,6 +315,7 @@ 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/include/windowapi.h b/src/include/windowapi.h
index 8557464..1d676e8 100644
--- a/src/include/windowapi.h
+++ b/src/include/windowapi.h
@@ -46,6 +46,8 @@ extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
 extern int64 WinGetCurrentPosition(WindowObject winobj);
 extern int64 WinGetPartitionRowCount(WindowObject winobj);
 
+extern int	WinGetFrameOptions(WindowObject winobj);
+
 extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
 
 extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
diff --git a/src/test/regress/expected/window.out b/src/test/regress/expected/window.out
index c2cc742..6b84dc1 100644
--- a/src/test/regress/expected/window.out
+++ b/src/test/regress/expected/window.out
@@ -1781,3 +1781,216 @@ SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
  5 | t | t        | t
 (5 rows)
 
+-- check we haven't reserved words that might break backwards-compatibility:
+CREATE TABLE reserved (
+  ignore text,
+  respect text,
+  nulls text
+);
+DROP TABLE reserved;
+-- testing ignore nulls functionality
+CREATE TEMPORARY TABLE dogs (
+    name text,
+    breed text,
+    age smallint
+);
+INSERT INTO dogs VALUES
+('K-9',          'robot', NULL),
+('alfred',          NULL,    8),
+('bones',     'shar pei', NULL),
+('churchill',  'bulldog', NULL),
+('lassie',          NULL,    4),
+('mickey',      'poodle',    7),
+('molly',       'poodle', NULL),
+('rover',     'shar pei',    3);
+-- test view definitions are preserved
+CREATE TEMP VIEW v_dogs AS
+  SELECT
+    name,
+    sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+    lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+    lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+  FROM dogs
+  WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_dogs');
+                                          pg_get_viewdef                                          
+--------------------------------------------------------------------------------------------------
+  SELECT dogs.name,                                                                              +
+     sum(dogs.age) OVER (ORDER BY dogs.age ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows,+
+     lag(dogs.age, 1) IGNORE NULLS OVER (ORDER BY dogs.name DESC) AS lagged_by_1,                +
+     lag(dogs.age, 2) IGNORE NULLS OVER w AS lagged_by_2                                         +
+    FROM dogs                                                                                    +
+   WINDOW w AS (ORDER BY dogs.name);
+(1 row)
+
+-- (1) lags by constant
+SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |   8
+ churchill |    
+ lassie    |    
+ mickey    |   4
+ molly     |   7
+ rover     |    
+(8 rows)
+
+SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |   8
+ churchill |    
+ lassie    |    
+ mickey    |   4
+ molly     |   7
+ rover     |    
+(8 rows)
+
+SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |   8
+ churchill |   8
+ lassie    |   8
+ mickey    |   4
+ molly     |   7
+ rover     |   7
+(8 rows)
+
+-- (2) leads by constant
+SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |    8
+ alfred    |     
+ bones     |     
+ churchill |    4
+ lassie    |    7
+ mickey    |     
+ molly     |    3
+ rover     |     
+(8 rows)
+
+SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |    8
+ alfred    |     
+ bones     |     
+ churchill |    4
+ lassie    |    7
+ mickey    |     
+ molly     |    3
+ rover     |     
+(8 rows)
+
+SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |    8
+ alfred    |    4
+ bones     |    4
+ churchill |    4
+ lassie    |    7
+ mickey    |    3
+ molly     |    3
+ rover     |     
+(8 rows)
+
+-- (3) lags by expression
+SELECT name, lag(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |  16
+ churchill |    
+ lassie    |    
+ mickey    |   8
+ molly     |  14
+ rover     |    
+(8 rows)
+
+SELECT name, lag(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |  16
+ churchill |    
+ lassie    |    
+ mickey    |   8
+ molly     |  14
+ rover     |    
+(8 rows)
+
+SELECT name, lag(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lag 
+-----------+-----
+ K-9       |    
+ alfred    |    
+ bones     |  16
+ churchill |  16
+ lassie    |  16
+ mickey    |   8
+ molly     |  14
+ rover     |  14
+(8 rows)
+
+-- (4) leads by expression
+SELECT name, lead(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |   16
+ alfred    |     
+ bones     |     
+ churchill |    8
+ lassie    |   14
+ mickey    |     
+ molly     |    6
+ rover     |     
+(8 rows)
+
+SELECT name, lead(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |   16
+ alfred    |     
+ bones     |     
+ churchill |    8
+ lassie    |   14
+ mickey    |     
+ molly     |    6
+ rover     |     
+(8 rows)
+
+SELECT name, lead(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+   name    | lead 
+-----------+------
+ K-9       |   16
+ alfred    |    8
+ bones     |    8
+ churchill |    8
+ lassie    |   14
+ mickey    |    6
+ molly     |    6
+ rover     |     
+(8 rows)
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY na...
+                     ^
+SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+LINE 1: SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM...
+                     ^
+DROP TABLE dogs CASCADE;
+NOTICE:  drop cascades to view v_dogs
diff --git a/src/test/regress/sql/window.sql b/src/test/regress/sql/window.sql
index 31c98eb..13c0a7b 100644
--- a/src/test/regress/sql/window.sql
+++ b/src/test/regress/sql/window.sql
@@ -621,3 +621,66 @@ 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);
+
+-- check we haven't reserved words that might break backwards-compatibility:
+CREATE TABLE reserved (
+  ignore text,
+  respect text,
+  nulls text
+);
+DROP TABLE reserved;
+
+-- testing ignore nulls functionality
+
+CREATE TEMPORARY TABLE dogs (
+    name text,
+    breed text,
+    age smallint
+);
+
+INSERT INTO dogs VALUES
+('K-9',          'robot', NULL),
+('alfred',          NULL,    8),
+('bones',     'shar pei', NULL),
+('churchill',  'bulldog', NULL),
+('lassie',          NULL,    4),
+('mickey',      'poodle',    7),
+('molly',       'poodle', NULL),
+('rover',     'shar pei',    3);
+
+-- test view definitions are preserved
+CREATE TEMP VIEW v_dogs AS
+  SELECT
+    name,
+    sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+    lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+    lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+  FROM dogs
+  WINDOW w as (ORDER BY name ASC);
+SELECT pg_get_viewdef('v_dogs');
+
+-- (1) lags by constant
+SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+
+-- (2) leads by constant
+SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+
+-- (3) lags by expression
+SELECT name, lag(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lag(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lag(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+
+-- (4) leads by expression
+SELECT name, lead(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lead(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, lead(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+
+-- these should be errors as the functionality isn't implemented yet:
+SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+
+DROP TABLE dogs CASCADE;
\ No newline at end of file

*** a/doc/src/sgml/func.sgml
--- b/doc/src/sgml/func.sgml
***************
*** 13164,13169 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
--- 13164,13170 ----
           lag(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+          [ { RESPECT | IGNORE } NULLS ]
         </function>
        </entry>
        <entry>
***************
*** 13178,13184 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null
        </entry>
       </row>
  
--- 13179,13187 ----
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null. If
!        <literal>IGNORE NULLS</> is specified then the function will be evaluated
!        as if the rows containing nulls didn't exist.
        </entry>
       </row>
  
***************
*** 13191,13196 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
--- 13194,13200 ----
           lead(<replaceable class="parameter">value</replaceable> <type>any</>
                [, <replaceable class="parameter">offset</replaceable> <type>integer</>
                [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+          [ { RESPECT | IGNORE } NULLS ]
         </function>
        </entry>
        <entry>
***************
*** 13205,13211 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null
        </entry>
       </row>
  
--- 13209,13217 ----
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null. If
!        <literal>IGNORE NULLS</> is specified then the function will be evaluated
!        as if the rows containing nulls didn't exist.
        </entry>
       </row>
  
***************
*** 13299,13309 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
    <note>
     <para>
      The SQL standard defines a <literal>RESPECT NULLS</> or
!     <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
!     <function>first_value</>, <function>last_value</>, and
!     <function>nth_value</>.  This is not implemented in
!     <productname>PostgreSQL</productname>: the behavior is always the
!     same as the standard's default, namely <literal>RESPECT NULLS</>.
      Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
      option for <function>nth_value</> is not implemented: only the
      default <literal>FROM FIRST</> behavior is supported.  (You can achieve
--- 13305,13314 ----
    <note>
     <para>
      The SQL standard defines a <literal>RESPECT NULLS</> or
!     <literal>IGNORE NULLS</> option for <function>first_value</>,
!     <function>last_value</>, and <function>nth_value</>.  This is not
!     implemented in <productname>PostgreSQL</productname>: the behavior is
!     always the same as the standard's default, namely <literal>RESPECT NULLS</>.
      Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
      option for <function>nth_value</> is not implemented: only the
      default <literal>FROM FIRST</> behavior is supported.  (You can achieve
*** a/src/backend/executor/nodeWindowAgg.c
--- b/src/backend/executor/nodeWindowAgg.c
***************
*** 2458,2464 **** window_gettupleslot(WindowObject winobj, int64 pos, TupleTableSlot *slot)
   * API exposed to window functions
   ***********************************************************************/
  
- 
  /*
   * WinGetPartitionLocalMemory
   *		Get working memory that lives till end of partition processing
--- 2458,2463 ----
***************
*** 2494,2499 **** WinGetCurrentPosition(WindowObject winobj)
--- 2493,2509 ----
  }
  
  /*
+  * WinGetFrameOptions
+  *		Returns the frame option flags
+  */
+ int
+ WinGetFrameOptions(WindowObject winobj)
+ {
+ 	Assert(WindowObjectIsValid(winobj));
+ 	return winobj->winstate->frameOptions;
+ }
+ 
+ /*
   * WinGetPartitionRowCount
   *		Return total number of rows contained in the current partition.
   *
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 293,298 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
--- 293,299 ----
  %type <list>	TriggerEvents TriggerOneEvent
  %type <value>	TriggerFuncArg
  %type <node>	TriggerWhen
+ %type <ival>	opt_ignore_nulls
  
  %type <list>	event_trigger_when_list event_trigger_value_list
  %type <defelt>	event_trigger_when_item
***************
*** 556,562 **** 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 IN_P
  	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
--- 557,563 ----
  
  	HANDLER HAVING HEADER_P HOLD HOUR_P
  
! 	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IN_P
  	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
***************
*** 586,592 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  
  	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
  	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
! 	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
  	ROW ROWS RULE
  
  	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
--- 587,593 ----
  
  	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
  	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
! 	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
  	ROW ROWS RULE
  
  	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
***************
*** 11900,11918 **** window_definition:
  				}
  		;
  
! over_clause: OVER window_specification
! 				{ $$ = $2; }
! 			| OVER ColId
  				{
  					WindowDef *n = makeNode(WindowDef);
! 					n->name = $2;
  					n->refname = NULL;
  					n->partitionClause = NIL;
  					n->orderClause = NIL;
! 					n->frameOptions = FRAMEOPTION_DEFAULTS;
  					n->startOffset = NULL;
  					n->endOffset = NULL;
! 					n->location = @2;
  					$$ = n;
  				}
  			| /*EMPTY*/
--- 11901,11928 ----
  				}
  		;
  
! opt_ignore_nulls:
! 			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
! 			| RESPECT NULLS_P					{ $$ = 0; }
! 			| /* EMPTY */						{ $$ = 0; }
! 		;
! 
! over_clause: opt_ignore_nulls OVER window_specification
! 				{
! 					$3->frameOptions |= $1;
! 					$$ = $3;
! 				}
! 			| opt_ignore_nulls OVER ColId
  				{
  					WindowDef *n = makeNode(WindowDef);
! 					n->name = $3;
  					n->refname = NULL;
  					n->partitionClause = NIL;
  					n->orderClause = NIL;
! 					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
  					n->startOffset = NULL;
  					n->endOffset = NULL;
! 					n->location = @3;
  					$$ = n;
  				}
  			| /*EMPTY*/
***************
*** 12906,12911 **** unreserved_keyword:
--- 12916,12922 ----
  			| HOUR_P
  			| IDENTITY_P
  			| IF_P
+ 			| IGNORE
  			| IMMEDIATE
  			| IMMUTABLE
  			| IMPLICIT_P
***************
*** 12993,12998 **** unreserved_keyword:
--- 13004,13010 ----
  			| REPLACE
  			| REPLICA
  			| RESET
+ 			| RESPECT
  			| RESTART
  			| RESTRICT
  			| RETURNS
*** a/src/backend/parser/parse_agg.c
--- b/src/backend/parser/parse_agg.c
***************
*** 694,721 **** transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
  	{
  		Index		winref = 0;
  		ListCell   *lc;
  
  		Assert(windef->refname == NULL &&
  			   windef->partitionClause == NIL &&
! 			   windef->orderClause == NIL &&
! 			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
  
  		foreach(lc, pstate->p_windowdefs)
  		{
! 			WindowDef  *refwin = (WindowDef *) lfirst(lc);
! 
  			winref++;
! 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
  			{
  				wfunc->winref = winref;
  				break;
  			}
  		}
! 		if (lc == NULL)			/* didn't find it? */
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("window \"%s\" does not exist", windef->name),
  					 parser_errposition(pstate, windef->location)));
  	}
  	else
  	{
--- 694,775 ----
  	{
  		Index		winref = 0;
  		ListCell   *lc;
+ 		WindowDef  *refwin = NULL;
  
  		Assert(windef->refname == NULL &&
  			   windef->partitionClause == NIL &&
! 			   windef->orderClause == NIL);
  
  		foreach(lc, pstate->p_windowdefs)
  		{
! 			WindowDef *thiswin = (WindowDef *) lfirst(lc);
  			winref++;
! 
! 			if (thiswin->name && strcmp(thiswin->name, windef->name) == 0)
! 			{
! 				/*
! 				 * "thiswin" is the window we want - but we have to tweak the
! 				 * definition slightly as some window options (e.g. IGNORE
! 				 * NULLS) can't be specified a standalone window definition;
! 				 * they can only be specified when invoking a window function
! 				 * over a window definition. However, we don't want to modify
! 				 * the window def itself (as that'll affect other window
! 				 * functions that use it - so if we need to make changes to it
! 				 * we'll clone refwin, change the clone and add the clone to
! 				 * the list of window definitions in pstate.
! 				 *
! 				 * There's one catch: what if a statement has two (or more)
! 				 * window function calls that reference the same window
! 				 * definition, and both have IGNORE NULLs? We don't want to
! 				 * add two modified definitions to pstate, so we'll only break
! 				 * if thiswin is an exact match - if not we'll keep looking for
! 				 * a window definition with the same name *and* same frame
! 				 * options.
! 				 */
! 				wfunc->winref = winref;
! 				refwin = thiswin;
! 				if(windef->frameOptions == FRAMEOPTION_DEFAULTS)
! 					break; /* don't need to clone, so just use this one */
! 			}
! 
! 			if (refwin && /* we need to have found the parent window */
! 				thiswin->refname &&
! 				strcmp(thiswin->refname, windef->name) == 0 && /* it reference the right parent */
! 				thiswin->frameOptions == windef->frameOptions)
  			{
+ 				/* found a clone window specification that we can re-use */
  				wfunc->winref = winref;
+ 				refwin = thiswin;
  				break;
  			}
  		}
! 
! 		if (refwin == NULL)			/* didn't find it? */
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("window \"%s\" does not exist", windef->name),
  					 parser_errposition(pstate, windef->location)));
+ 		else if (windef->frameOptions != refwin->frameOptions /* we can't use the clone */
+ 			&& windef->frameOptions != FRAMEOPTION_DEFAULTS) /* we can't use the parent */
+ 		{
+ 			/*
+ 			 * This means we've found the parent, but no clones (if there were
+ 			 * any) had the correct frame options. We'll clone the parent we
+ 			 * found (refwin), set the frame options we want and add the new
+ 			 * clone to pstate:
+ 			 */
+ 			WindowDef *clone = makeNode(WindowDef);
+ 
+ 			clone->name = NULL;
+ 			clone->refname = pstrdup(refwin->name);
+ 			clone->frameOptions = windef->frameOptions; /* Note windef! */
+ 			clone->startOffset = copyObject(refwin->startOffset);
+ 			clone->endOffset = copyObject(refwin->endOffset);
+ 			clone->location = refwin->location;
+ 
+ 			pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+ 			wfunc->winref = list_length(pstate->p_windowdefs);
+ 		}
  	}
  	else
  	{
*** a/src/backend/parser/parse_func.c
--- b/src/backend/parser/parse_func.c
***************
*** 726,731 **** ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
--- 726,747 ----
  							NameListToString(funcname)),
  					 parser_errposition(pstate, location)));
  
+ 		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+ 		{
+ 			/*
+ 			 * As this is only implemented for the lead & lag window functions
+ 			 * we'll filter out all aggregate functions too.
+ 			 */
+ 			if (fdresult != FUNCDETAIL_WINDOWFUNC
+ 				|| (strcmp("lead", strVal(llast(funcname))) != 0 &&
+ 					strcmp("lag", strVal(llast(funcname))) != 0))
+ 			{
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 						 errmsg("RESPECT NULLS is only implemented for the lead and lag window functions"),
+ 						 parser_errposition(pstate, location)));			}
+ 		}
+ 
  		/*
  		 * ordered aggs not allowed in windows yet
  		 */
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
***************
*** 4982,4992 **** get_rule_windowspec(WindowClause *wc, List *targetList,
  	bool		needspace = false;
  	const char *sep;
  	ListCell   *l;
  
  	appendStringInfoChar(buf, '(');
  	if (wc->refname)
  	{
! 		appendStringInfoString(buf, quote_identifier(wc->refname));
  		needspace = true;
  	}
  	/* partition clauses are always inherited, so only print if no refname */
--- 4982,4997 ----
  	bool		needspace = false;
  	const char *sep;
  	ListCell   *l;
+ 	size_t		refname_len = 0;
+ 	int			initial_buf_len = buf->len;
  
  	appendStringInfoChar(buf, '(');
  	if (wc->refname)
  	{
! 		const char *quoted_refname = quote_identifier(wc->refname);
! 
! 		refname_len = strlen(quoted_refname);
! 		appendStringInfoString(buf, quoted_refname);
  		needspace = true;
  	}
  	/* partition clauses are always inherited, so only print if no refname */
***************
*** 5068,5074 **** get_rule_windowspec(WindowClause *wc, List *targetList,
  		/* we will now have a trailing space; remove it */
  		buf->len--;
  	}
! 	appendStringInfoChar(buf, ')');
  }
  
  /* ----------
--- 5073,5092 ----
  		/* we will now have a trailing space; remove it */
  		buf->len--;
  	}
! 
! 	/*
! 	 * We'll tidy up the output slightly; if we've got a refname, but haven't
! 	 * overridden the partition-by, order-by or any of the frame flags
! 	 * relevant inside the window def's ()s, then we'll be left with
! 	 * "(<refname>)". We'll trim off the brackets in this case:
! 	 */
! 	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
! 	{
! 		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
! 		buf->len -= 1;			/* the trailing ")" */
! 	}
! 	else
! 		appendStringInfoChar(buf, ')');
  }
  
  /* ----------
***************
*** 7860,7866 **** get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
  		get_rule_expr((Node *) wfunc->aggfilter, context, false);
  	}
  
! 	appendStringInfoString(buf, ") OVER ");
  
  	foreach(l, context->windowClause)
  	{
--- 7878,7884 ----
  		get_rule_expr((Node *) wfunc->aggfilter, context, false);
  	}
  
! 	appendStringInfoString(buf, ") ");
  
  	foreach(l, context->windowClause)
  	{
***************
*** 7868,7873 **** get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
--- 7886,7895 ----
  
  		if (wc->winref == wfunc->winref)
  		{
+ 			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+ 				appendStringInfoString(buf, "IGNORE NULLS ");
+ 			appendStringInfoString(buf, "OVER ");
+ 
  			if (wc->name)
  				appendStringInfoString(buf, quote_identifier(wc->name));
  			else
*** a/src/backend/utils/adt/windowfuncs.c
--- b/src/backend/utils/adt/windowfuncs.c
***************
*** 13,19 ****
--- 13,21 ----
   */
  #include "postgres.h"
  
+ #include "nodes/bitmapset.h"
  #include "utils/builtins.h"
+ #include "utils/memutils.h"
  #include "windowapi.h"
  
  /*
***************
*** 24,29 **** typedef struct rank_context
--- 26,47 ----
  	int64		rank;			/* current rank */
  } rank_context;
  
+ 
+ typedef struct leadlag_const_context
+ {
+ 	/* the index of the lead / lagged value */
+ 	int64		next;
+ 
+ 	/* how many non-NULL tuples before we can start emitting? */
+ 	int64		lag_wait;
+ }	leadlag_const_context;
+ 
+ /*
+  * lead-lag process helpers
+  */
+ #define ISNULL_INDEX(i) (2 * (i))
+ #define HAVESCANNED_INDEX(i) ((2 * (i)) + 1)
+ 
  /*
   * ntile process information
   */
***************
*** 38,43 **** typedef struct
--- 56,65 ----
  static bool rank_up(WindowObject winobj);
  static Datum leadlag_common(FunctionCallInfo fcinfo,
  			   bool forward, bool withoffset, bool withdefault);
+ static Datum win_get_arg_ignore_nulls(WindowObject winobj, int argno,
+ 									  int offset, int seektype,
+ 									  bool const_offset, bool *isnull,
+ 									  bool *isout);
  
  
  /*
***************
*** 280,286 **** window_ntile(PG_FUNCTION_ARGS)
   * common operation of lead() and lag()
   * For lead() forward is true, whereas for lag() it is false.
   * withoffset indicates we have an offset second argument.
!  * withdefault indicates we have a default third argument.
   */
  static Datum
  leadlag_common(FunctionCallInfo fcinfo,
--- 302,309 ----
   * common operation of lead() and lag()
   * For lead() forward is true, whereas for lag() it is false.
   * withoffset indicates we have an offset second argument.
!  * withdefault indicates we have a default third argument. We'll only
!  *	return this default if the offset we want is outside of the partition.
   */
  static Datum
  leadlag_common(FunctionCallInfo fcinfo,
***************
*** 290,303 **** leadlag_common(FunctionCallInfo fcinfo,
  	int32		offset;
  	bool		const_offset;
  	Datum		result;
! 	bool		isnull;
! 	bool		isout;
  
  	if (withoffset)
  	{
  		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
  		if (isnull)
  			PG_RETURN_NULL();
  		const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
  	}
  	else
--- 313,337 ----
  	int32		offset;
  	bool		const_offset;
  	Datum		result;
! 	bool		isnull = false;
! 	bool		isout = false;
! 	bool		ignore_nulls;
! 
! 	/* is IGNORE NULLS specified? */
! 	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
  
  	if (withoffset)
  	{
  		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
  		if (isnull)
  			PG_RETURN_NULL();
+ 
+ 		/*
+ 		 * We want to set the markpos (the earliest tuple we can access) as
+ 		 * aggressively as possible to save memory, but if the offset isn't
+ 		 * constant we really need random access on the partition (so can't
+ 		 * mark at all).
+ 		 */
  		const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
  	}
  	else
***************
*** 305,325 **** leadlag_common(FunctionCallInfo fcinfo,
  		offset = 1;
  		const_offset = true;
  	}
  
! 	result = WinGetFuncArgInPartition(winobj, 0,
! 									  (forward ? offset : -offset),
! 									  WINDOW_SEEK_CURRENT,
! 									  const_offset,
! 									  &isnull, &isout);
  
  	if (isout)
  	{
  		/*
! 		 * target row is out of the partition; supply default value if
! 		 * provided.  otherwise it'll stay NULL
  		 */
  		if (withdefault)
  			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
  	}
  
  	if (isnull)
--- 339,382 ----
  		offset = 1;
  		const_offset = true;
  	}
+ 	if (!forward)
+ 	{
+ 		offset = -offset;
+ 	}
  
! 	if (ignore_nulls)
! 	{
! 		result = win_get_arg_ignore_nulls(winobj, 0,
! 										  offset,
! 										  WINDOW_SEEK_CURRENT,
! 										  const_offset,
! 										  &isnull, &isout);
! 	}
! 	else
! 	{
! 		result = WinGetFuncArgInPartition(winobj, 0,
! 										  offset,
! 										  WINDOW_SEEK_CURRENT,
! 										  const_offset,
! 										  &isnull, &isout);
! 	}
  
  	if (isout)
  	{
  		/*
! 		 * Target row is out of the partition; supply default value if
! 		 * provided.
  		 */
  		if (withdefault)
  			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+ 		else
+ 		{
+ 			/*
+ 			 * Don't return whatever's lying around in result, force the
+ 			 * output to null if there's no default.
+ 			 */
+ 			Assert(isnull);
+ 		}
  	}
  
  	if (isnull)
***************
*** 329,334 **** leadlag_common(FunctionCallInfo fcinfo,
--- 386,714 ----
  }
  
  /*
+  * win_get_arg_ignore_nulls
+  *
+  * Like WinGetFuncArgInPartition, but skips over any rows where the argument
+  * evaluates to NULL as though they did not exist. Offset is relative to the
+  * current row (positive or negative). If offset is zero, *isout is set false,
+  * and the argument at the current row is returned, even if it is NULL.
+  *
+  * Some argument names differ from WinGetFuncArgInPartition, but the meanings
+  * are the same.
+  */
+ static Datum
+ win_get_arg_ignore_nulls(WindowObject winobj, int argno,
+ 						 int offset, int seektype, bool const_offset,
+ 						 bool *result_isnull, bool *result_isout)
+ {
+ 	/*
+ 	 * A ** pointer as we keep a Bitmapset * in the partition context, and
+ 	 * WinGetPartitionLocalMemory returns a pointer to whatever's in the
+ 	 * context.
+ 	 */
+ 	Bitmapset **null_values;
+ 	bool local_isout = false;
+ 	bool local_isnull = false;
+ 	Datum result;
+ 
+ 	/*
+ 	 * Special case: when applying the offset, we're ignoring all rows where
+ 	 * the argument evaluates to NULL. But if the offset is zero, the standard
+ 	 * requires that we evaluate the argument at the current row even if it is
+ 	 * NULL.
+ 	 */
+ 	if (offset == 0)
+ 	{
+ 		result = WinGetFuncArgInPartition(winobj, 0,
+ 										  offset,
+ 										  WINDOW_SEEK_CURRENT,
+ 										  const_offset,
+ 										  result_isnull, result_isout);
+ 		Assert (*result_isout == false);
+ 		return result;
+ 	}
+ 
+ 	if (const_offset)
+ 	{
+ 		leadlag_const_context *context;
+ 
+ 		/*
+ 		 * For positive offset, the mark will always be set to the current
+ 		 * row. We initialize by scanning until we find 'offset' non-NULL
+ 		 * values, and remember that index in a context variable, 'next'. Each
+ 		 * time this function is called, if the current argument value is
+ 		 * NULL, we just return the same value. If the current row is
+ 		 * non-NULL, we scan forward to find one more non-NULL value, update
+ 		 * 'next' to that index, and return the new value.
+ 		 *
+ 		 * For a negative offset, the mark will always be set to the index of
+ 		 * the 'offset'th non-NULL value before the current row if it
+ 		 * exists. In addition to 'next', we also need to track another
+ 		 * context variable 'lag_wait'; otherwise we don't know if we've
+ 		 * actually seen 'offset' non-NULL values or not. The 'lag_wait' is
+ 		 * initialized to 'offset' and counts down with each non-NULL value
+ 		 * encountered, always returning NULL until it reaches zero. When
+ 		 * lag_count is zero, we save the value at 'next'. If the argument
+ 		 * value at the current row is NULL, we then scan forward until we
+ 		 * find the next non-NULL value, and mark it and update 'next'. The
+ 		 * saved value is returned.
+ 		 */
+ 
+ 		context = WinGetPartitionLocalMemory(winobj,
+ 											 sizeof(leadlag_const_context));
+ 
+ 		/*
+ 		 * First time through, initialize.
+ 		 */
+ 		if (WinGetCurrentPosition(winobj) == 0)
+ 		{
+ 			/*
+ 			 * If offset is positive, we need to scan through looking for
+ 			 * 'offset' non-NULL values. Do not set the mark.
+ 			 */
+ 			if (offset >= 0)
+ 			{
+ 				int i, j;
+ 
+ 				for (i = 0, j = -1; i < offset && !local_isout; i++)
+ 				{
+ 					do
+ 					{
+ 						j++;
+ 						result = WinGetFuncArgInPartition(winobj, 0,
+ 														  j,
+ 														  WINDOW_SEEK_HEAD,
+ 														  false,
+ 														  &local_isnull,
+ 														  &local_isout);
+ 					}
+ 					while (local_isnull && !local_isout);
+ 				}
+ 
+ 				context->next = j;
+ 				context->lag_wait = 0;
+ 			}
+ 			else
+ 			{
+ 				/* 'next' will be incremented before being read */
+ 				context->next = -1;
+ 				context->lag_wait = -offset;
+ 			}
+ 		}
+ 
+ 		/*
+ 		 * Look at the current row to check whether it's NULL or not. If the
+ 		 * offset is positive, use this opportunity to mark the position;
+ 		 * otherwise it will be done later.
+ 		 */
+ 		WinGetFuncArgInPartition(winobj, 0,
+ 								 0,
+ 								 WINDOW_SEEK_CURRENT,
+ 								 (offset >= 0),
+ 								 &local_isnull, &local_isout);
+ 
+ 		/* offset negative, and haven't seen enough non-NULL values yet */
+ 		if (context->lag_wait > 0)
+ 		{
+ 			if (!local_isnull)
+ 				context->lag_wait--;
+ 
+ 			/* track the current position */
+ 			context->next++;
+ 
+ 			*result_isnull = true;
+ 			*result_isout = false;
+ 			return (Datum) 0;
+ 		}
+ 
+ 		/*
+ 		 * For negative offset, we fetch the value from before the scan.
+ 		 */
+ 		if (offset < 0)
+ 		{
+ 			result = WinGetFuncArgInPartition(winobj, 0,
+ 											  context->next,
+ 											  WINDOW_SEEK_HEAD,
+ 											  false,
+ 											  result_isnull, result_isout);
+ 		}
+ 
+ 		if (!local_isnull)
+ 		{
+ 			int i = context->next;
+ 
+ 			do
+ 			{
+ 				i++;
+ 				WinGetFuncArgInPartition(winobj, 0,
+ 										 i,
+ 										 WINDOW_SEEK_HEAD,
+ 										 (offset < 0),
+ 										 &local_isnull, &local_isout);
+ 			}
+ 			while (local_isnull && !local_isout);
+ 
+ 			context->next = i;
+ 		}
+ 
+ 		/*
+ 		 * For positive offset, we fetch the value from after the scan.
+ 		 */
+ 		if (offset >= 0)
+ 		{
+ 			result = WinGetFuncArgInPartition(winobj, 0,
+ 											  context->next,
+ 											  WINDOW_SEEK_HEAD,
+ 											  false,
+ 											  result_isnull, result_isout);
+ 		}
+ 
+ 		return result;
+ 	}
+ 	else
+ 	{
+ 		int64		scanning,
+ 			current = WinGetCurrentPosition(winobj);
+ 
+ 		bool local_forward = (offset >= 0);
+ 
+ 		/*
+ 		 * This case is a little complicated; we're defining "IGNORE NULLS" as
+ 		 * "run the query, and pretend the rows with nulls in them don't
+ 		 * exist". This means that we'll scan from the current row an 'offset'
+ 		 * number of non-null rows, and then return that one.
+ 		 *
+ 		 * As the offset isn't constant we need efficient random access to the
+ 		 * partition, as we'll check upto O(partition size) tuples for each
+ 		 * row we're calculating the window function value for.
+ 		 */
+ 
+ 		null_values = (Bitmapset **) WinGetPartitionLocalMemory(winobj, sizeof(Bitmapset *));
+ 
+ 		if (*null_values == NULL)
+ 		{
+ 			MemoryContext oldcxt;
+ 
+ 			/*
+ 			 * Accessing tuples is expensive, so we'll keep track of the ones
+ 			 * we've accessed (more specifically, if they're null or not).
+ 			 * We'll need one bit for whether the value is null and one bit
+ 			 * for whether we've checked that tuple or not. We'll keep these
+ 			 * two bits together (as opposed to having two separate bitmaps)
+ 			 * to improve cache locality.
+ 			 *
+ 			 * However, we'd lose the efficient gains if we keep having to
+ 			 * resize the Bitmapset (by setting higher and higher bits). We
+ 			 * know the maximum number of bits we'll ever need, so we'll use
+ 			 * bms_make_singleton to force our Bitmapset up to the required
+ 			 * size.
+ 			 */
+ 			int64		bits_needed = 2 * WinGetPartitionRowCount(winobj);
+ 
+ 			oldcxt = MemoryContextSwitchTo(GetMemoryChunkContext(null_values));
+ 			*null_values = bms_make_singleton(bits_needed + 1);
+ 			MemoryContextSwitchTo(oldcxt);
+ 		}
+ 
+ 		/*
+ 		 * We use offset >= 0 instead of just forward as the offset might be
+ 		 * in the opposite direction to the way we're scanning. We'll then
+ 		 * force offset to be positive to make counting down the rows easier.
+ 		 */
+ 		local_forward = offset == 0 ? local_forward : (offset > 0);
+ 		offset = abs(offset);
+ 
+ 		for (scanning = current;; local_forward ? ++scanning : --scanning)
+ 		{
+ 			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+ 			{
+ 				local_isout = true;
+ 
+ 				/*
+ 				 * As we're out of the window we want to return NULL or the
+ 				 * default value, but not whatever's left in result. We'll use
+ 				 * the isnull flag to say "ignore it"!
+ 				 */
+ 				local_isnull = true;
+ 				result = (Datum) 0;
+ 
+ 				break;
+ 			}
+ 
+ 			if (bms_is_member(HAVESCANNED_INDEX(scanning), *null_values))
+ 			{
+ 				local_isnull = bms_is_member(ISNULL_INDEX(scanning), *null_values);
+ 			}
+ 			else
+ 			{
+ 				/*
+ 				 * first time we've accessed this index; let's see if it's
+ 				 * null:
+ 				 */
+ 				result = WinGetFuncArgInPartition(winobj, 0,
+ 												  scanning,
+ 												  WINDOW_SEEK_HEAD,
+ 												  false,
+ 												  &local_isnull, &local_isout);
+ 				if (local_isout)
+ 					break;
+ 
+ 				bms_add_member(*null_values, HAVESCANNED_INDEX(scanning));
+ 				if (local_isnull)
+ 				{
+ 					bms_add_member(*null_values, ISNULL_INDEX(scanning));
+ 				}
+ 			}
+ 
+ 			/*
+ 			 * Now the isnull flag is set correctly. If !isnull there's a
+ 			 * chance that we may stop iterating here:
+ 			 */
+ 			if (!local_isnull)
+ 			{
+ 				if (offset == 0)
+ 				{
+ 					result = WinGetFuncArgInPartition(winobj, 0,
+ 													  scanning,
+ 													  WINDOW_SEEK_HEAD,
+ 													  false,
+ 													  &local_isnull, &local_isout);
+ 					break;
+ 				}
+ 				else
+ 					--offset;	/* it's not null, so we're one step closer to
+ 								 * the value we want */
+ 			}
+ 			else if (scanning == current)
+ 			{
+ 				/*--------
+ 				 * A slight edge case. Consider:
+ 				 *
+ 				 * =================
+ 				 *	 A	 | lag(A, 1)
+ 				 * =================
+ 				 *	 1	 |	 NULL
+ 				 *	 2	 |	  1
+ 				 *	NULL |	  ?
+ 				 * =================
+ 				 *
+ 				 * Does a lag of one when the current value is null mean go back to the first
+ 				 * non-null value (i.e. 2), or find the previous non-null value of the first
+ 				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+ 				 * need to correct slightly:
+ 				 *--------
+ 				 */
+ 				--offset;
+ 			}
+ 		}
+ 	}
+ 
+ 	*result_isnull = local_isnull;
+ 	*result_isout = local_isout;
+ 	return result;
+ }
+ 
+ /*
   * lag
   * returns the value of VE evaluated on a row that is 1
   * row before the current row within a partition,
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 420,438 **** typedef struct SortBy
   * For entries in a WINDOW list, "name" is the window name being defined.
   * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
   * for the "OVER (window)" syntax, which is subtly different --- the latter
!  * implies overriding the window frame clause.
   */
  typedef struct WindowDef
  {
  	NodeTag		type;
! 	char	   *name;			/* window's own name */
! 	char	   *refname;		/* referenced window name, if any */
! 	List	   *partitionClause;	/* PARTITION BY expression list */
! 	List	   *orderClause;	/* ORDER BY (list of SortBy) */
! 	int			frameOptions;	/* frame_clause options, see below */
! 	Node	   *startOffset;	/* expression for starting bound, if any */
! 	Node	   *endOffset;		/* expression for ending bound, if any */
! 	int			location;		/* parse location, or -1 if none/unknown */
  } WindowDef;
  
  /*
--- 420,457 ----
   * For entries in a WINDOW list, "name" is the window name being defined.
   * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
   * for the "OVER (window)" syntax, which is subtly different --- the latter
!  * implies overriding the window frame clause. The semantics of each override
!  * depends on the field.
   */
  typedef struct WindowDef
  {
  	NodeTag		type;
! 	/* Window's own name. This must be NULL for overrides. */
! 	char	   *name;
! 	/* Referenced window name, if any. This must be present on overrides. */
! 	char	   *refname;
! 	/*
! 	 * PARTITION BY expression list. If an override leaves this NULL, the
! 	 * parent's partitionClause will be used.
! 	 */
! 	List	   *partitionClause;
! 	/*
! 	 * ORDER BY (list of SortBy). This field is ignored in overrides - the
! 	 * parent's value will always be used.
! 	 */
! 	List	   *orderClause;
! 	/*
! 	 * The remaining fields in this struct must be specified on overrides,
! 	 * even if the override's value is the same as the parent's.
! 	 */
! 	/* frame_clause options, see below */
! 	int			frameOptions;
! 	/* Expression for starting bound, if any */
! 	Node	   *startOffset;
! 	/* expression for ending bound, if any */
! 	Node	   *endOffset;
! 	/* parse location, or -1 if none/unknown */
! 	int			location;
  } WindowDef;
  
  /*
***************
*** 457,462 **** typedef struct WindowDef
--- 476,482 ----
  #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
  #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
  #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+ #define FRAMEOPTION_IGNORE_NULLS				0x04000
  
  #define FRAMEOPTION_START_VALUE \
  	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 180,185 **** PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
--- 180,186 ----
  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, UNRESERVED_KEYWORD)
  PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
  PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
  PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
***************
*** 312,317 **** PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
--- 313,319 ----
  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)
*** a/src/include/windowapi.h
--- b/src/include/windowapi.h
***************
*** 46,51 **** extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
--- 46,53 ----
  extern int64 WinGetCurrentPosition(WindowObject winobj);
  extern int64 WinGetPartitionRowCount(WindowObject winobj);
  
+ extern int	WinGetFrameOptions(WindowObject winobj);
+ 
  extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
  
  extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
*** a/src/test/regress/expected/window.out
--- b/src/test/regress/expected/window.out
***************
*** 1822,1824 **** SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
--- 1822,2064 ----
   5 | t | t        | t
  (5 rows)
  
+ -- check we haven't reserved words that might break backwards-compatibility:
+ CREATE TABLE reserved (
+   ignore text,
+   respect text,
+   nulls text
+ );
+ DROP TABLE reserved;
+ -- testing ignore nulls functionality
+ CREATE TEMPORARY TABLE dogs (
+     name text,
+     breed text,
+     age smallint
+ );
+ INSERT INTO dogs VALUES
+ ('ajax',          'mythological', NULL),
+ ('alfred',          NULL,    8),
+ ('bones',     'shar pei', NULL),
+ ('churchill',  'bulldog', NULL),
+ ('lassie',          NULL,    4),
+ ('mickey',      'poodle',    7),
+ ('molly',       'poodle', NULL),
+ ('rover',     'shar pei',    3);
+ -- test view definitions are preserved
+ CREATE TEMP VIEW v_dogs AS
+   SELECT
+     name,
+     sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+     lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+     lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+   FROM dogs
+   WINDOW w as (ORDER BY name ASC);
+ SELECT pg_get_viewdef('v_dogs');
+                                           pg_get_viewdef                                          
+ --------------------------------------------------------------------------------------------------
+   SELECT dogs.name,                                                                              +
+      sum(dogs.age) OVER (ORDER BY dogs.age ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows,+
+      lag(dogs.age, 1) IGNORE NULLS OVER (ORDER BY dogs.name DESC) AS lagged_by_1,                +
+      lag(dogs.age, 2) IGNORE NULLS OVER w AS lagged_by_2                                         +
+     FROM dogs                                                                                    +
+    WINDOW w AS (ORDER BY dogs.name);
+ (1 row)
+ 
+ -- (1) lags by constant
+ SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |    
+  lassie    |    
+  mickey    |   4
+  molly     |   7
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |    
+  lassie    |    
+  mickey    |   4
+  molly     |   7
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |   8
+  lassie    |   8
+  mickey    |   4
+  molly     |   7
+  rover     |   7
+ (8 rows)
+ 
+ -- (2) leads by constant
+ SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |     
+  bones     |     
+  churchill |    4
+  lassie    |    7
+  mickey    |     
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |     
+  bones     |     
+  churchill |    4
+  lassie    |    7
+  mickey    |     
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |    4
+  bones     |    4
+  churchill |    4
+  lassie    |    7
+  mickey    |    3
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ -- (3) lags by expression
+ SELECT name, lag(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |    
+  lassie    |    
+  mickey    |   8
+  molly     |  14
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |    
+  lassie    |    
+  mickey    |   8
+  molly     |  14
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |  16
+  lassie    |  16
+  mickey    |   8
+  molly     |  14
+  rover     |  14
+ (8 rows)
+ 
+ -- (4) leads by expression
+ SELECT name, lead(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |     
+  bones     |     
+  churchill |    8
+  lassie    |   14
+  mickey    |     
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |     
+  bones     |     
+  churchill |    8
+  lassie    |   14
+  mickey    |     
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |    8
+  bones     |    8
+  churchill |    8
+  lassie    |   14
+  mickey    |    6
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ -- these should be errors as the functionality isn't implemented yet:
+ SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+ LINE 1: SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY na...
+                      ^
+ SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ ERROR:  RESPECT NULLS is only implemented for the lead and lag window functions
+ LINE 1: SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM...
+                      ^
+ -- ensure that a zero offset still returns the current value, even if NULL
+ SELECT name, lead(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |     
+  alfred    |    8
+  bones     |     
+  churchill |     
+  lassie    |    4
+  mickey    |    7
+  molly     |     
+  rover     |    3
+ (8 rows)
+ 
+ SELECT name, lag(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |   8
+  bones     |    
+  churchill |    
+  lassie    |   4
+  mickey    |   7
+  molly     |    
+  rover     |   3
+ (8 rows)
+ 
+ DROP TABLE dogs CASCADE;
+ NOTICE:  drop cascades to view v_dogs
*** a/src/test/regress/sql/window.sql
--- b/src/test/regress/sql/window.sql
***************
*** 641,643 **** SELECT to_char(SUM(n::float8) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FO
--- 641,710 ----
  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);
+ 
+ -- check we haven't reserved words that might break backwards-compatibility:
+ CREATE TABLE reserved (
+   ignore text,
+   respect text,
+   nulls text
+ );
+ DROP TABLE reserved;
+ 
+ -- testing ignore nulls functionality
+ 
+ CREATE TEMPORARY TABLE dogs (
+     name text,
+     breed text,
+     age smallint
+ );
+ 
+ INSERT INTO dogs VALUES
+ ('ajax',          'mythological', NULL),
+ ('alfred',          NULL,    8),
+ ('bones',     'shar pei', NULL),
+ ('churchill',  'bulldog', NULL),
+ ('lassie',          NULL,    4),
+ ('mickey',      'poodle',    7),
+ ('molly',       'poodle', NULL),
+ ('rover',     'shar pei',    3);
+ 
+ -- test view definitions are preserved
+ CREATE TEMP VIEW v_dogs AS
+   SELECT
+     name,
+     sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+     lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+     lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+   FROM dogs
+   WINDOW w as (ORDER BY name ASC);
+ SELECT pg_get_viewdef('v_dogs');
+ 
+ -- (1) lags by constant
+ SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (2) leads by constant
+ SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (3) lags by expression
+ SELECT name, lag(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (4) leads by expression
+ SELECT name, lead(age * 2) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age * 2) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age * 2) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- these should be errors as the functionality isn't implemented yet:
+ SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- ensure that a zero offset still returns the current value, even if NULL
+ SELECT name, lead(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ DROP TABLE dogs CASCADE;

*** a/doc/src/sgml/func.sgml
--- b/doc/src/sgml/func.sgml
***************
*** 13164,13169 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
--- 13164,13170 ----
           lag(<replaceable class="parameter">value</replaceable> <type>any</>
               [, <replaceable class="parameter">offset</replaceable> <type>integer</>
               [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+          [ { RESPECT | IGNORE } NULLS ]
         </function>
        </entry>
        <entry>
***************
*** 13178,13184 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null
        </entry>
       </row>
  
--- 13179,13187 ----
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null. If
!        <literal>IGNORE NULLS</> is specified then the function will be evaluated
!        as if the rows containing nulls didn't exist.
        </entry>
       </row>
  
***************
*** 13191,13196 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
--- 13194,13200 ----
           lead(<replaceable class="parameter">value</replaceable> <type>any</>
                [, <replaceable class="parameter">offset</replaceable> <type>integer</>
                [, <replaceable class="parameter">default</replaceable> <type>any</> ]])
+          [ { RESPECT | IGNORE } NULLS ]
         </function>
        </entry>
        <entry>
***************
*** 13205,13211 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null
        </entry>
       </row>
  
--- 13209,13217 ----
         <replaceable class="parameter">default</replaceable> are evaluated
         with respect to the current row.  If omitted,
         <replaceable class="parameter">offset</replaceable> defaults to 1 and
!        <replaceable class="parameter">default</replaceable> to null. If
!        <literal>IGNORE NULLS</> is specified then the function will be evaluated
!        as if the rows containing nulls didn't exist.
        </entry>
       </row>
  
***************
*** 13299,13309 **** SELECT xmlagg(x) FROM (SELECT x FROM test ORDER BY y DESC) AS tab;
    <note>
     <para>
      The SQL standard defines a <literal>RESPECT NULLS</> or
!     <literal>IGNORE NULLS</> option for <function>lead</>, <function>lag</>,
!     <function>first_value</>, <function>last_value</>, and
!     <function>nth_value</>.  This is not implemented in
!     <productname>PostgreSQL</productname>: the behavior is always the
!     same as the standard's default, namely <literal>RESPECT NULLS</>.
      Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
      option for <function>nth_value</> is not implemented: only the
      default <literal>FROM FIRST</> behavior is supported.  (You can achieve
--- 13305,13314 ----
    <note>
     <para>
      The SQL standard defines a <literal>RESPECT NULLS</> or
!     <literal>IGNORE NULLS</> option for <function>first_value</>,
!     <function>last_value</>, and <function>nth_value</>.  This is not
!     implemented in <productname>PostgreSQL</productname>: the behavior is
!     always the same as the standard's default, namely <literal>RESPECT NULLS</>.
      Likewise, the standard's <literal>FROM FIRST</> or <literal>FROM LAST</>
      option for <function>nth_value</> is not implemented: only the
      default <literal>FROM FIRST</> behavior is supported.  (You can achieve
*** a/src/backend/executor/nodeWindowAgg.c
--- b/src/backend/executor/nodeWindowAgg.c
***************
*** 2494,2499 **** WinGetCurrentPosition(WindowObject winobj)
--- 2494,2510 ----
  }
  
  /*
+  * WinGetFrameOptions
+  *		Returns the frame option flags
+  */
+ int
+ WinGetFrameOptions(WindowObject winobj)
+ {
+ 	Assert(WindowObjectIsValid(winobj));
+ 	return winobj->winstate->frameOptions;
+ }
+ 
+ /*
   * WinGetPartitionRowCount
   *		Return total number of rows contained in the current partition.
   *
*** a/src/backend/parser/gram.y
--- b/src/backend/parser/gram.y
***************
*** 301,306 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
--- 301,307 ----
  %type <list>	TriggerEvents TriggerOneEvent
  %type <value>	TriggerFuncArg
  %type <node>	TriggerWhen
+ %type <ival>	opt_ignore_nulls
  
  %type <list>	event_trigger_when_list event_trigger_value_list
  %type <defelt>	event_trigger_when_item
***************
*** 566,572 **** 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
  	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
--- 567,573 ----
  
  	HANDLER HAVING HEADER_P HOLD HOUR_P
  
! 	IDENTITY_P IF_P IGNORE ILIKE IMMEDIATE IMMUTABLE IMPLICIT_P IMPORT_P IN_P
  	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
***************
*** 596,602 **** static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
  
  	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
  	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
! 	RESET RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
  	ROW ROWS RULE
  
  	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
--- 597,603 ----
  
  	RANGE READ REAL REASSIGN RECHECK RECURSIVE REF REFERENCES REFRESH REINDEX
  	RELATIVE_P RELEASE RENAME REPEATABLE REPLACE REPLICA
! 	RESET RESPECT RESTART RESTRICT RETURNING RETURNS REVOKE RIGHT ROLE ROLLBACK
  	ROW ROWS RULE
  
  	SAVEPOINT SCHEMA SCROLL SEARCH SECOND_P SECURITY SELECT SEQUENCE SEQUENCES
***************
*** 11957,11975 **** window_definition:
  				}
  		;
  
! over_clause: OVER window_specification
! 				{ $$ = $2; }
! 			| OVER ColId
  				{
  					WindowDef *n = makeNode(WindowDef);
! 					n->name = $2;
  					n->refname = NULL;
  					n->partitionClause = NIL;
  					n->orderClause = NIL;
! 					n->frameOptions = FRAMEOPTION_DEFAULTS;
  					n->startOffset = NULL;
  					n->endOffset = NULL;
! 					n->location = @2;
  					$$ = n;
  				}
  			| /*EMPTY*/
--- 11958,11985 ----
  				}
  		;
  
! opt_ignore_nulls:
! 			IGNORE NULLS_P						{ $$ = FRAMEOPTION_IGNORE_NULLS; }
! 			| RESPECT NULLS_P					{ $$ = 0; }
! 			| /* EMPTY */						{ $$ = 0; }
! 		;
! 
! over_clause: opt_ignore_nulls OVER window_specification
! 				{
! 					$3->frameOptions |= $1;
! 					$$ = $3;
! 				}
! 			| opt_ignore_nulls OVER ColId
  				{
  					WindowDef *n = makeNode(WindowDef);
! 					n->name = $3;
  					n->refname = NULL;
  					n->partitionClause = NIL;
  					n->orderClause = NIL;
! 					n->frameOptions = FRAMEOPTION_DEFAULTS | $1;
  					n->startOffset = NULL;
  					n->endOffset = NULL;
! 					n->location = @3;
  					$$ = n;
  				}
  			| /*EMPTY*/
***************
*** 12963,12968 **** unreserved_keyword:
--- 12973,12979 ----
  			| HOUR_P
  			| IDENTITY_P
  			| IF_P
+ 			| IGNORE
  			| IMMEDIATE
  			| IMMUTABLE
  			| IMPLICIT_P
***************
*** 13051,13056 **** unreserved_keyword:
--- 13062,13068 ----
  			| REPLACE
  			| REPLICA
  			| RESET
+ 			| RESPECT
  			| RESTART
  			| RESTRICT
  			| RETURNS
*** a/src/backend/parser/parse_agg.c
--- b/src/backend/parser/parse_agg.c
***************
*** 694,721 **** transformWindowFuncCall(ParseState *pstate, WindowFunc *wfunc,
  	{
  		Index		winref = 0;
  		ListCell   *lc;
  
  		Assert(windef->refname == NULL &&
  			   windef->partitionClause == NIL &&
! 			   windef->orderClause == NIL &&
! 			   windef->frameOptions == FRAMEOPTION_DEFAULTS);
  
  		foreach(lc, pstate->p_windowdefs)
  		{
! 			WindowDef  *refwin = (WindowDef *) lfirst(lc);
! 
  			winref++;
! 			if (refwin->name && strcmp(refwin->name, windef->name) == 0)
  			{
  				wfunc->winref = winref;
  				break;
  			}
  		}
! 		if (lc == NULL)			/* didn't find it? */
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("window \"%s\" does not exist", windef->name),
  					 parser_errposition(pstate, windef->location)));
  	}
  	else
  	{
--- 694,775 ----
  	{
  		Index		winref = 0;
  		ListCell   *lc;
+ 		WindowDef  *refwin = NULL;
  
  		Assert(windef->refname == NULL &&
  			   windef->partitionClause == NIL &&
! 			   windef->orderClause == NIL);
  
  		foreach(lc, pstate->p_windowdefs)
  		{
! 			WindowDef *thiswin = (WindowDef *) lfirst(lc);
  			winref++;
! 
! 			if (thiswin->name && strcmp(thiswin->name, windef->name) == 0)
! 			{
! 				/*
! 				 * "thiswin" is the window we want - but we have to tweak the
! 				 * definition slightly as some window options (e.g. IGNORE
! 				 * NULLS) can't be specified a standalone window definition;
! 				 * they can only be specified when invoking a window function
! 				 * over a window definition. However, we don't want to modify
! 				 * the window def itself (as that'll affect other window
! 				 * functions that use it - so if we need to make changes to it
! 				 * we'll clone refwin, change the clone and add the clone to
! 				 * the list of window definitions in pstate.
! 				 *
! 				 * There's one catch: what if a statement has two (or more)
! 				 * window function calls that reference the same window
! 				 * definition, and both have IGNORE NULLs? We don't want to
! 				 * add two modified definitions to pstate, so we'll only break
! 				 * if thiswin is an exact match - if not we'll keep looking for
! 				 * a window definition with the same name *and* same frame
! 				 * options.
! 				 */
! 				wfunc->winref = winref;
! 				refwin = thiswin;
! 				if(windef->frameOptions == FRAMEOPTION_DEFAULTS)
! 					break; /* don't need to clone, so just use this one */
! 			}
! 
! 			if (refwin && /* we need to have found the parent window */
! 				thiswin->refname &&
! 				strcmp(thiswin->refname, windef->name) == 0 && /* it reference the right parent */
! 				thiswin->frameOptions == windef->frameOptions)
  			{
+ 				/* found a clone window specification that we can re-use */
  				wfunc->winref = winref;
+ 				refwin = thiswin;
  				break;
  			}
  		}
! 
! 		if (refwin == NULL)			/* didn't find it? */
  			ereport(ERROR,
  					(errcode(ERRCODE_UNDEFINED_OBJECT),
  					 errmsg("window \"%s\" does not exist", windef->name),
  					 parser_errposition(pstate, windef->location)));
+ 		else if (windef->frameOptions != refwin->frameOptions /* we can't use the clone */
+ 			&& windef->frameOptions != FRAMEOPTION_DEFAULTS) /* we can't use the parent */
+ 		{
+ 			/*
+ 			 * This means we've found the parent, but no clones (if there were
+ 			 * any) had the correct frame options. We'll clone the parent we
+ 			 * found (refwin), set the frame options we want and add the new
+ 			 * clone to pstate:
+ 			 */
+ 			WindowDef *clone = makeNode(WindowDef);
+ 
+ 			clone->name = NULL;
+ 			clone->refname = pstrdup(refwin->name);
+ 			clone->frameOptions = windef->frameOptions; /* Note windef! */
+ 			clone->startOffset = copyObject(refwin->startOffset);
+ 			clone->endOffset = copyObject(refwin->endOffset);
+ 			clone->location = refwin->location;
+ 
+ 			pstate->p_windowdefs = lappend(pstate->p_windowdefs, clone);
+ 			wfunc->winref = list_length(pstate->p_windowdefs);
+ 		}
  	}
  	else
  	{
*** a/src/backend/parser/parse_func.c
--- b/src/backend/parser/parse_func.c
***************
*** 726,731 **** ParseFuncOrColumn(ParseState *pstate, List *funcname, List *fargs,
--- 726,747 ----
  							NameListToString(funcname)),
  					 parser_errposition(pstate, location)));
  
+ 		if (over->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+ 		{
+ 			/*
+ 			 * As this is only implemented for the lead & lag window functions
+ 			 * we'll filter out all aggregate functions too.
+ 			 */
+ 			if (fdresult != FUNCDETAIL_WINDOWFUNC
+ 				|| (strcmp("lead", strVal(llast(funcname))) != 0 &&
+ 					strcmp("lag", strVal(llast(funcname))) != 0))
+ 			{
+ 				ereport(ERROR,
+ 						(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+ 						 errmsg("IGNORE NULLS is only implemented for the lead and lag window functions"),
+ 						 parser_errposition(pstate, location)));			}
+ 		}
+ 
  		/*
  		 * ordered aggs not allowed in windows yet
  		 */
*** a/src/backend/utils/adt/ruleutils.c
--- b/src/backend/utils/adt/ruleutils.c
***************
*** 4982,4992 **** get_rule_windowspec(WindowClause *wc, List *targetList,
  	bool		needspace = false;
  	const char *sep;
  	ListCell   *l;
  
  	appendStringInfoChar(buf, '(');
  	if (wc->refname)
  	{
! 		appendStringInfoString(buf, quote_identifier(wc->refname));
  		needspace = true;
  	}
  	/* partition clauses are always inherited, so only print if no refname */
--- 4982,4997 ----
  	bool		needspace = false;
  	const char *sep;
  	ListCell   *l;
+ 	size_t		refname_len = 0;
+ 	int			initial_buf_len = buf->len;
  
  	appendStringInfoChar(buf, '(');
  	if (wc->refname)
  	{
! 		const char *quoted_refname = quote_identifier(wc->refname);
! 
! 		refname_len = strlen(quoted_refname);
! 		appendStringInfoString(buf, quoted_refname);
  		needspace = true;
  	}
  	/* partition clauses are always inherited, so only print if no refname */
***************
*** 5068,5074 **** get_rule_windowspec(WindowClause *wc, List *targetList,
  		/* we will now have a trailing space; remove it */
  		buf->len--;
  	}
! 	appendStringInfoChar(buf, ')');
  }
  
  /* ----------
--- 5073,5092 ----
  		/* we will now have a trailing space; remove it */
  		buf->len--;
  	}
! 
! 	/*
! 	 * We'll tidy up the output slightly; if we've got a refname, but haven't
! 	 * overridden the partition-by, order-by or any of the frame flags
! 	 * relevant inside the window def's ()s, then we'll be left with
! 	 * "(<refname>)". We'll trim off the brackets in this case:
! 	 */
! 	if (wc->refname && buf->len == initial_buf_len + refname_len + 1)
! 	{
! 		memcpy(buf->data + initial_buf_len, buf->data + initial_buf_len + 1, refname_len);
! 		buf->len -= 1;			/* the trailing ")" */
! 	}
! 	else
! 		appendStringInfoChar(buf, ')');
  }
  
  /* ----------
***************
*** 7860,7866 **** get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
  		get_rule_expr((Node *) wfunc->aggfilter, context, false);
  	}
  
! 	appendStringInfoString(buf, ") OVER ");
  
  	foreach(l, context->windowClause)
  	{
--- 7878,7884 ----
  		get_rule_expr((Node *) wfunc->aggfilter, context, false);
  	}
  
! 	appendStringInfoString(buf, ") ");
  
  	foreach(l, context->windowClause)
  	{
***************
*** 7868,7873 **** get_windowfunc_expr(WindowFunc *wfunc, deparse_context *context)
--- 7886,7895 ----
  
  		if (wc->winref == wfunc->winref)
  		{
+ 			if (wc->frameOptions & FRAMEOPTION_IGNORE_NULLS)
+ 				appendStringInfoString(buf, "IGNORE NULLS ");
+ 			appendStringInfoString(buf, "OVER ");
+ 
  			if (wc->name)
  				appendStringInfoString(buf, quote_identifier(wc->name));
  			else
*** a/src/backend/utils/adt/windowfuncs.c
--- b/src/backend/utils/adt/windowfuncs.c
***************
*** 13,19 ****
--- 13,21 ----
   */
  #include "postgres.h"
  
+ #include "nodes/bitmapset.h"
  #include "utils/builtins.h"
+ #include "utils/memutils.h"
  #include "windowapi.h"
  
  /*
***************
*** 24,29 **** typedef struct rank_context
--- 26,53 ----
  	int64		rank;			/* current rank */
  } rank_context;
  
+ 
+ typedef struct leadlag_const_context
+ {
+ 	/* the index of the lead / lagged value */
+ 	int64		current_nonnull;
+ 
+ 	/* how many non-NULL tuples before we can start emitting? */
+ 	int64		lag_wait;
+ }	leadlag_const_context;
+ 
+ /*
+  * lead-lag process helpers
+  */
+ #define BITMAP_EXISTS(bitmap, index) \
+ 	(((bitmap)[(index) / 4] >> (((index) % 4)*2 + 0)) & 0x01)
+ #define BITMAP_NONNULL(bitmap, index) \
+ 	(((bitmap)[(index) / 4] >> (((index) % 4)*2 + 1)) & 0x01)
+ #define BITMAP_SET_EXISTS(bitmap, index) \
+ 	((bitmap)[(index) / 4] |= (0x1 << (((index) % 4)*2 + 0)))
+ #define BITMAP_SET_NONNULL(bitmap, index) \
+ 	((bitmap)[(index) / 4] |= (0x1 << (((index) % 4)*2 + 1)))
+ 
  /*
   * ntile process information
   */
***************
*** 38,43 **** typedef struct
--- 62,71 ----
  static bool rank_up(WindowObject winobj);
  static Datum leadlag_common(FunctionCallInfo fcinfo,
  			   bool forward, bool withoffset, bool withdefault);
+ static Datum win_get_arg_ignore_nulls(WindowObject winobj, int argno,
+ 									  int offset, int seektype,
+ 									  bool const_offset, bool *isnull,
+ 									  bool *isout);
  
  
  /*
***************
*** 280,286 **** window_ntile(PG_FUNCTION_ARGS)
   * common operation of lead() and lag()
   * For lead() forward is true, whereas for lag() it is false.
   * withoffset indicates we have an offset second argument.
!  * withdefault indicates we have a default third argument.
   */
  static Datum
  leadlag_common(FunctionCallInfo fcinfo,
--- 308,315 ----
   * common operation of lead() and lag()
   * For lead() forward is true, whereas for lag() it is false.
   * withoffset indicates we have an offset second argument.
!  * withdefault indicates we have a default third argument. We'll only
!  *	return this default if the offset we want is outside of the partition.
   */
  static Datum
  leadlag_common(FunctionCallInfo fcinfo,
***************
*** 290,303 **** leadlag_common(FunctionCallInfo fcinfo,
  	int32		offset;
  	bool		const_offset;
  	Datum		result;
! 	bool		isnull;
! 	bool		isout;
  
  	if (withoffset)
  	{
  		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
  		if (isnull)
  			PG_RETURN_NULL();
  		const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
  	}
  	else
--- 319,343 ----
  	int32		offset;
  	bool		const_offset;
  	Datum		result;
! 	bool		isnull = false;
! 	bool		isout = false;
! 	bool		ignore_nulls;
! 
! 	/* is IGNORE NULLS specified? */
! 	ignore_nulls = (WinGetFrameOptions(winobj) & FRAMEOPTION_IGNORE_NULLS) != 0;
  
  	if (withoffset)
  	{
  		offset = DatumGetInt32(WinGetFuncArgCurrent(winobj, 1, &isnull));
  		if (isnull)
  			PG_RETURN_NULL();
+ 
+ 		/*
+ 		 * We want to set the markpos (the earliest tuple we can access) as
+ 		 * aggressively as possible to save memory, but if the offset isn't
+ 		 * constant we really need random access on the partition (so can't
+ 		 * mark at all).
+ 		 */
  		const_offset = get_fn_expr_arg_stable(fcinfo->flinfo, 1);
  	}
  	else
***************
*** 305,325 **** leadlag_common(FunctionCallInfo fcinfo,
  		offset = 1;
  		const_offset = true;
  	}
  
! 	result = WinGetFuncArgInPartition(winobj, 0,
! 									  (forward ? offset : -offset),
! 									  WINDOW_SEEK_CURRENT,
! 									  const_offset,
! 									  &isnull, &isout);
  
  	if (isout)
  	{
  		/*
! 		 * target row is out of the partition; supply default value if
! 		 * provided.  otherwise it'll stay NULL
  		 */
  		if (withdefault)
  			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
  	}
  
  	if (isnull)
--- 345,388 ----
  		offset = 1;
  		const_offset = true;
  	}
+ 	if (!forward)
+ 	{
+ 		offset = -offset;
+ 	}
  
! 	if (ignore_nulls)
! 	{
! 		result = win_get_arg_ignore_nulls(winobj, 0,
! 										  offset,
! 										  WINDOW_SEEK_CURRENT,
! 										  const_offset,
! 										  &isnull, &isout);
! 	}
! 	else
! 	{
! 		result = WinGetFuncArgInPartition(winobj, 0,
! 										  offset,
! 										  WINDOW_SEEK_CURRENT,
! 										  const_offset,
! 										  &isnull, &isout);
! 	}
  
  	if (isout)
  	{
  		/*
! 		 * Target row is out of the partition; supply default value if
! 		 * provided.
  		 */
  		if (withdefault)
  			result = WinGetFuncArgCurrent(winobj, 2, &isnull);
+ 		else
+ 		{
+ 			/*
+ 			 * Don't return whatever's lying around in result, force the
+ 			 * output to null if there's no default.
+ 			 */
+ 			Assert(isnull);
+ 		}
  	}
  
  	if (isnull)
***************
*** 329,334 **** leadlag_common(FunctionCallInfo fcinfo,
--- 392,674 ----
  }
  
  /*
+  * win_get_arg_ignore_nulls
+  *
+  * Like WinGetFuncArgInPartition, but skips over any rows where the argument
+  * evaluates to NULL as though they did not exist. Offset is relative to the
+  * current row (positive or negative). If offset is zero, *isout is set false,
+  * and the argument at the current row is returned, even if it is NULL.
+  *
+  * Some argument names differ from WinGetFuncArgInPartition, but the meanings
+  * are the same.
+  */
+ static Datum
+ win_get_arg_ignore_nulls(WindowObject winobj, int argno,
+ 						 int offset, int seektype, bool const_offset,
+ 						 bool *result_isnull, bool *result_isout)
+ {
+ 	bool local_isout = false;
+ 	bool local_isnull = false;
+ 	Datum result;
+ 
+ 	Assert(seektype == WINDOW_SEEK_CURRENT);
+ 
+ 	/*
+ 	 * Special case: when applying the offset, we're ignoring all rows where
+ 	 * the argument evaluates to NULL. But if the offset is zero, the standard
+ 	 * requires that we evaluate the argument at the current row even if it is
+ 	 * NULL.
+ 	 */
+ 	if (offset == 0)
+ 	{
+ 		result = WinGetFuncArgInPartition(winobj, 0,
+ 										  offset,
+ 										  WINDOW_SEEK_CURRENT,
+ 										  const_offset,
+ 										  result_isnull, result_isout);
+ 		Assert (*result_isout == false);
+ 		return result;
+ 	}
+ 
+ 	if (const_offset)
+ 	{
+ 		leadlag_const_context *context;
+ 
+ 		/*
+ 		 * When the offset is constant, we can mark the position of the first
+ 		 * tuple we'll need. This optimization allows unneeded tuples to be
+ 		 * freed, which also avoids searching through them unnecessarily.
+ 		 *
+ 		 * For a positive offset, the mark will be set to the current row,
+ 		 * because we need to know whether it's NULL.
+ 		 *
+ 		 * For a negative offset, the mark will always be set to the index of
+ 		 * the 'offset'th non-NULL value before the current row, if it
+ 		 * exists.
+ 		 */
+ 
+ 		context = WinGetPartitionLocalMemory(winobj,
+ 											 sizeof(leadlag_const_context));
+ 
+ 		/*
+ 		 * First time through, initialize.
+ 		 */
+ 		if (WinGetCurrentPosition(winobj) == 0)
+ 		{
+ 			context->current_nonnull = -1;
+ 
+ 			/*
+ 			 * If offset is positive, scan until 'offset' non-NULL values are
+ 			 * seen, updating 'current_nonnull'. Do not set the mark.
+ 			 */
+ 			if (offset >= 0)
+ 			{
+ 				int i;
+ 
+ 				for (i = 0; i < offset && !local_isout; i++)
+ 				{
+ 					do
+ 					{
+ 						WinGetFuncArgInPartition(winobj, 0,
+ 												 ++context->current_nonnull,
+ 												 WINDOW_SEEK_HEAD,
+ 												 false,
+ 												 &local_isnull,
+ 												 &local_isout);
+ 					}
+ 					while (local_isnull && !local_isout);
+ 				}
+ 
+ 				context->lag_wait = 0;
+ 			}
+ 			else
+ 				context->lag_wait = -offset;
+ 		}
+ 
+ 		/*
+ 		 * Look at the current row to check whether it's NULL or not. If the
+ 		 * offset is positive, use this opportunity to mark the position;
+ 		 * otherwise it will be done later.
+ 		 */
+ 		WinGetFuncArgInPartition(winobj, 0,
+ 								 0,
+ 								 WINDOW_SEEK_CURRENT,
+ 								 (offset >= 0),
+ 								 &local_isnull, &local_isout);
+ 
+ 		/* offset negative, and haven't seen enough non-NULL values yet */
+ 		if (context->lag_wait > 0)
+ 		{
+ 			if (!local_isnull)
+ 			{
+ 				context->lag_wait--;
+ 				if (context->current_nonnull == -1)
+ 					context->current_nonnull = WinGetCurrentPosition(winobj);
+ 			}
+ 
+ 			*result_isnull = true;
+ 			*result_isout = true;
+ 			return (Datum) 0;
+ 		}
+ 
+ 		/* For negative offset, we fetch the value before scanning forward */
+ 		if (offset < 0)
+ 			result = WinGetFuncArgInPartition(winobj, 0,
+ 											  context->current_nonnull,
+ 											  WINDOW_SEEK_HEAD,
+ 											  false,
+ 											  result_isnull, result_isout);
+ 
+ 		/*
+ 		 * If the current position's value is non-NULL, scan forward to find
+ 		 * the next non-NULL value and update 'current_nonnull'. If offset is
+ 		 * negative, then mark it.
+ 		 *
+ 		 * If the current position's value is NULL, then nothing changes.
+ 		 */
+ 		if (!local_isnull)
+ 		{
+ 			do
+ 			{
+ 				WinGetFuncArgInPartition(winobj, 0,
+ 										 ++context->current_nonnull,
+ 										 WINDOW_SEEK_HEAD,
+ 										 (offset < 0),
+ 										 &local_isnull, &local_isout);
+ 			}
+ 			while (local_isnull && !local_isout);
+ 		}
+ 
+ 		/* For positive offset, we fetch the value after scanning forward */
+ 		if (offset >= 0)
+ 			result = WinGetFuncArgInPartition(winobj, 0,
+ 											  context->current_nonnull,
+ 											  WINDOW_SEEK_HEAD,
+ 											  false,
+ 											  result_isnull, result_isout);
+ 
+ 		return result;
+ 	}
+ 	else
+ 	{
+ 		char *bitmap;
+ 		int64		scanning,
+ 			current = WinGetCurrentPosition(winobj);
+ 
+ 		bool local_forward = (offset >= 0);
+ 
+ 		/*
+ 		 * Create a bitmap with at least 2 * n positions. The first bit
+ 		 * records whether we've examined that row before, and the second
+ 		 * records whether it's non-NULL. No initialization is required,
+ 		 * because it begins with all zeros, as it should.
+ 		 *
+ 		 * This bitmap allows us to randomly access the 'offset'th non-NULL
+ 		 * value without scanning 'offset' (or more) tuple in the window each
+ 		 * time. We still have to scan forward through the bitmap to skip over
+ 		 * NULLs, but that's much cheaper.
+ 		 */
+ 		bitmap = WinGetPartitionLocalMemory(
+ 			winobj, (WinGetPartitionRowCount(winobj) / 4) + 1);
+ 
+ 		/*
+ 		 * We use offset >= 0 instead of just forward as the offset might be
+ 		 * in the opposite direction to the way we're scanning. We'll then
+ 		 * force offset to be positive to make counting down the rows easier.
+ 		 */
+ 		local_forward = offset == 0 ? local_forward : (offset > 0);
+ 		offset = abs(offset);
+ 
+ 		for (scanning = current;; local_forward ? ++scanning : --scanning)
+ 		{
+ 			if (scanning < 0 || scanning >= WinGetPartitionRowCount(winobj))
+ 			{
+ 				local_isout = true;
+ 
+ 				/*
+ 				 * As we're out of the window we want to return NULL or the
+ 				 * default value, but not whatever's left in result. We'll use
+ 				 * the isnull flag to say "ignore it"!
+ 				 */
+ 				local_isnull = true;
+ 				result = (Datum) 0;
+ 
+ 				break;
+ 			}
+ 
+ 			if (BITMAP_EXISTS(bitmap, scanning))
+ 			{
+ 				local_isnull = !BITMAP_NONNULL(bitmap, scanning);
+ 			}
+ 			else
+ 			{
+ 				/*
+ 				 * first time we've accessed this index; let's see if it's
+ 				 * null:
+ 				 */
+ 				result = WinGetFuncArgInPartition(winobj, 0,
+ 												  scanning,
+ 												  WINDOW_SEEK_HEAD,
+ 												  false,
+ 												  &local_isnull, &local_isout);
+ 				if (local_isout)
+ 					break;
+ 
+ 				BITMAP_SET_EXISTS(bitmap, scanning);
+ 				if (!local_isnull)
+ 					BITMAP_SET_NONNULL(bitmap, scanning);
+ 			}
+ 
+ 			/*
+ 			 * Now the isnull flag is set correctly. If !isnull there's a
+ 			 * chance that we may stop iterating here:
+ 			 */
+ 			if (!local_isnull)
+ 			{
+ 				if (offset == 0)
+ 				{
+ 					result = WinGetFuncArgInPartition(winobj, 0,
+ 													  scanning,
+ 													  WINDOW_SEEK_HEAD,
+ 													  false,
+ 													  &local_isnull, &local_isout);
+ 
+ 					break;
+ 				}
+ 				else
+ 					--offset;	/* it's not null, so we're one step closer to
+ 								 * the value we want */
+ 			}
+ 			else if (scanning == current)
+ 			{
+ 				/*--------
+ 				 * A slight edge case. Consider:
+ 				 *
+ 				 * =================
+ 				 *	 A	 | lag(A, 1)
+ 				 * =================
+ 				 *	 1	 |	 NULL
+ 				 *	 2	 |	  1
+ 				 *	NULL |	  ?
+ 				 * =================
+ 				 *
+ 				 * Does a lag of one when the current value is null mean go back to the first
+ 				 * non-null value (i.e. 2), or find the previous non-null value of the first
+ 				 * non-null value (i.e. 1)? We're implementing the former semantics, so we'll
+ 				 * need to correct slightly:
+ 				 *--------
+ 				 */
+ 				--offset;
+ 			}
+ 		}
+ 	}
+ 
+ 	*result_isnull = local_isnull;
+ 	*result_isout = local_isout;
+ 	return result;
+ }
+ 
+ /*
   * lag
   * returns the value of VE evaluated on a row that is 1
   * row before the current row within a partition,
*** a/src/include/nodes/parsenodes.h
--- b/src/include/nodes/parsenodes.h
***************
*** 420,438 **** typedef struct SortBy
   * For entries in a WINDOW list, "name" is the window name being defined.
   * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
   * for the "OVER (window)" syntax, which is subtly different --- the latter
!  * implies overriding the window frame clause.
   */
  typedef struct WindowDef
  {
  	NodeTag		type;
! 	char	   *name;			/* window's own name */
! 	char	   *refname;		/* referenced window name, if any */
! 	List	   *partitionClause;	/* PARTITION BY expression list */
! 	List	   *orderClause;	/* ORDER BY (list of SortBy) */
! 	int			frameOptions;	/* frame_clause options, see below */
! 	Node	   *startOffset;	/* expression for starting bound, if any */
! 	Node	   *endOffset;		/* expression for ending bound, if any */
! 	int			location;		/* parse location, or -1 if none/unknown */
  } WindowDef;
  
  /*
--- 420,457 ----
   * For entries in a WINDOW list, "name" is the window name being defined.
   * For OVER clauses, we use "name" for the "OVER window" syntax, or "refname"
   * for the "OVER (window)" syntax, which is subtly different --- the latter
!  * implies overriding the window frame clause. The semantics of each override
!  * depends on the field.
   */
  typedef struct WindowDef
  {
  	NodeTag		type;
! 	/* Window's own name. This must be NULL for overrides. */
! 	char	   *name;
! 	/* Referenced window name, if any. This must be present on overrides. */
! 	char	   *refname;
! 	/*
! 	 * PARTITION BY expression list. If an override leaves this NULL, the
! 	 * parent's partitionClause will be used.
! 	 */
! 	List	   *partitionClause;
! 	/*
! 	 * ORDER BY (list of SortBy). This field is ignored in overrides - the
! 	 * parent's value will always be used.
! 	 */
! 	List	   *orderClause;
! 	/*
! 	 * The remaining fields in this struct must be specified on overrides,
! 	 * even if the override's value is the same as the parent's.
! 	 */
! 	/* frame_clause options, see below */
! 	int			frameOptions;
! 	/* Expression for starting bound, if any */
! 	Node	   *startOffset;
! 	/* expression for ending bound, if any */
! 	Node	   *endOffset;
! 	/* parse location, or -1 if none/unknown */
! 	int			location;
  } WindowDef;
  
  /*
***************
*** 457,462 **** typedef struct WindowDef
--- 476,482 ----
  #define FRAMEOPTION_END_VALUE_PRECEDING			0x00800 /* end is V. P. */
  #define FRAMEOPTION_START_VALUE_FOLLOWING		0x01000 /* start is V. F. */
  #define FRAMEOPTION_END_VALUE_FOLLOWING			0x02000 /* end is V. F. */
+ #define FRAMEOPTION_IGNORE_NULLS				0x04000
  
  #define FRAMEOPTION_START_VALUE \
  	(FRAMEOPTION_START_VALUE_PRECEDING | FRAMEOPTION_START_VALUE_FOLLOWING)
*** a/src/include/parser/kwlist.h
--- b/src/include/parser/kwlist.h
***************
*** 180,185 **** PG_KEYWORD("hold", HOLD, UNRESERVED_KEYWORD)
--- 180,186 ----
  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, UNRESERVED_KEYWORD)
  PG_KEYWORD("ilike", ILIKE, TYPE_FUNC_NAME_KEYWORD)
  PG_KEYWORD("immediate", IMMEDIATE, UNRESERVED_KEYWORD)
  PG_KEYWORD("immutable", IMMUTABLE, UNRESERVED_KEYWORD)
***************
*** 313,318 **** PG_KEYWORD("repeatable", REPEATABLE, UNRESERVED_KEYWORD)
--- 314,320 ----
  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)
*** a/src/include/windowapi.h
--- b/src/include/windowapi.h
***************
*** 46,51 **** extern void *WinGetPartitionLocalMemory(WindowObject winobj, Size sz);
--- 46,53 ----
  extern int64 WinGetCurrentPosition(WindowObject winobj);
  extern int64 WinGetPartitionRowCount(WindowObject winobj);
  
+ extern int	WinGetFrameOptions(WindowObject winobj);
+ 
  extern void WinSetMarkPosition(WindowObject winobj, int64 markpos);
  
  extern bool WinRowsArePeers(WindowObject winobj, int64 pos1, int64 pos2);
*** a/src/test/regress/expected/window.out
--- b/src/test/regress/expected/window.out
***************
*** 1822,1824 **** SELECT i, b, bool_and(b) OVER w, bool_or(b) OVER w
--- 1822,2251 ----
   5 | t | t        | t
  (5 rows)
  
+ -- check we haven't reserved words that might break backwards-compatibility:
+ CREATE TABLE reserved (
+   ignore text,
+   respect text,
+   nulls text
+ );
+ DROP TABLE reserved;
+ -- testing ignore nulls functionality
+ CREATE TEMPORARY TABLE dogs (
+     name text,
+     breed text,
+     age int
+ );
+ INSERT INTO dogs VALUES
+ ('ajax',          'mythological', NULL),
+ ('alfred',          NULL,    8),
+ ('bones',     'shar pei', NULL),
+ ('churchill',  'bulldog', NULL),
+ ('lassie',          NULL,    4),
+ ('mickey',      'poodle',    7),
+ ('molly',       'poodle', NULL),
+ ('rover',     'shar pei',    3);
+ -- test view definitions are preserved
+ CREATE TEMP VIEW v_dogs AS
+   SELECT
+     name,
+     sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+     lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+     lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+   FROM dogs
+   WINDOW w as (ORDER BY name ASC);
+ SELECT pg_get_viewdef('v_dogs');
+                                           pg_get_viewdef                                          
+ --------------------------------------------------------------------------------------------------
+   SELECT dogs.name,                                                                              +
+      sum(dogs.age) OVER (ORDER BY dogs.age ROWS BETWEEN 1 PRECEDING AND 1 FOLLOWING) AS sum_rows,+
+      lag(dogs.age, 1) IGNORE NULLS OVER (ORDER BY dogs.name DESC) AS lagged_by_1,                +
+      lag(dogs.age, 2) IGNORE NULLS OVER w AS lagged_by_2                                         +
+     FROM dogs                                                                                    +
+    WINDOW w AS (ORDER BY dogs.name);
+ (1 row)
+ 
+ CREATE FUNCTION volatile_int(INT) RETURNS INT AS
+   $$ BEGIN RETURN $1; END; $$
+   LANGUAGE PLPGSQL VOLATILE;
+ -- (1) lags by constant
+ SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |    
+  lassie    |    
+  mickey    |   4
+  molly     |   7
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |    
+  lassie    |    
+  mickey    |   4
+  molly     |   7
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |   8
+  churchill |   8
+  lassie    |   8
+  mickey    |   4
+  molly     |   7
+  rover     |   7
+ (8 rows)
+ 
+ -- (2) leads by constant
+ SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |     
+  bones     |     
+  churchill |    4
+  lassie    |    7
+  mickey    |     
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |     
+  bones     |     
+  churchill |    4
+  lassie    |    7
+  mickey    |     
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |    4
+  bones     |    4
+  churchill |    4
+  lassie    |    7
+  mickey    |    3
+  molly     |    3
+  rover     |     
+ (8 rows)
+ 
+ -- (3) lags by expression
+ SELECT name, lag(age * 2, volatile_int(1)) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |    
+  lassie    |    
+  mickey    |   8
+  molly     |  14
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age * 2, volatile_int(1)) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |    
+  lassie    |    
+  mickey    |   8
+  molly     |  14
+  rover     |    
+ (8 rows)
+ 
+ SELECT name, lag(age * 2, volatile_int(1)) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |    
+  bones     |  16
+  churchill |  16
+  lassie    |  16
+  mickey    |   8
+  molly     |  14
+  rover     |  14
+ (8 rows)
+ 
+ -- (4) leads by expression
+ SELECT name, lead(age * 2, volatile_int(1)) OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |     
+  bones     |     
+  churchill |    8
+  lassie    |   14
+  mickey    |     
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age * 2, volatile_int(1)) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |     
+  bones     |     
+  churchill |    8
+  lassie    |   14
+  mickey    |     
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ SELECT name, lead(age * 2, volatile_int(1)) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |   16
+  alfred    |    8
+  bones     |    8
+  churchill |    8
+  lassie    |   14
+  mickey    |    6
+  molly     |    6
+  rover     |     
+ (8 rows)
+ 
+ -- (4) defaults
+ SELECT name, lead(age, 1, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |    4
+  bones     |    4
+  churchill |    4
+  lassie    |    7
+  mickey    |    3
+  molly     |    3
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lead(age, 2, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    4
+  alfred    |    7
+  bones     |    7
+  churchill |    7
+  lassie    |    3
+  mickey    |   -1
+  molly     |   -1
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lead(age, 3, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    7
+  alfred    |    3
+  bones     |    3
+  churchill |    3
+  lassie    |   -1
+  mickey    |   -1
+  molly     |   -1
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lead(age, volatile_int(1), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    8
+  alfred    |    4
+  bones     |    4
+  churchill |    4
+  lassie    |    7
+  mickey    |    3
+  molly     |    3
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lead(age, volatile_int(2), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    4
+  alfred    |    7
+  bones     |    7
+  churchill |    7
+  lassie    |    3
+  mickey    |   -1
+  molly     |   -1
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lead(age, volatile_int(3), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |    7
+  alfred    |    3
+  bones     |    3
+  churchill |    3
+  lassie    |   -1
+  mickey    |   -1
+  molly     |   -1
+  rover     |   -1
+ (8 rows)
+ 
+ SELECT name, lag(age, 1, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |   8
+  churchill |   8
+  lassie    |   8
+  mickey    |   4
+  molly     |   7
+  rover     |   7
+ (8 rows)
+ 
+ SELECT name, lag(age, 2, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |  -1
+  churchill |  -1
+  lassie    |  -1
+  mickey    |   8
+  molly     |   4
+  rover     |   4
+ (8 rows)
+ 
+ SELECT name, lag(age, 3, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |  -1
+  churchill |  -1
+  lassie    |  -1
+  mickey    |  -1
+  molly     |   8
+  rover     |   8
+ (8 rows)
+ 
+ SELECT name, lag(age, volatile_int(1), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |   8
+  churchill |   8
+  lassie    |   8
+  mickey    |   4
+  molly     |   7
+  rover     |   7
+ (8 rows)
+ 
+ SELECT name, lag(age, volatile_int(2), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |  -1
+  churchill |  -1
+  lassie    |  -1
+  mickey    |   8
+  molly     |   4
+  rover     |   4
+ (8 rows)
+ 
+ SELECT name, lag(age, volatile_int(3), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |  -1
+  alfred    |  -1
+  bones     |  -1
+  churchill |  -1
+  lassie    |  -1
+  mickey    |  -1
+  molly     |   8
+  rover     |   8
+ (8 rows)
+ 
+ -- these should be errors as the functionality isn't implemented yet:
+ SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ ERROR:  IGNORE NULLS is only implemented for the lead and lag window functions
+ LINE 1: SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY na...
+                      ^
+ SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ ERROR:  IGNORE NULLS is only implemented for the lead and lag window functions
+ LINE 1: SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM...
+                      ^
+ -- ensure that a zero offset still returns the current value, even if NULL
+ SELECT name, lead(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |     
+  alfred    |    8
+  bones     |     
+  churchill |     
+  lassie    |    4
+  mickey    |    7
+  molly     |     
+  rover     |    3
+ (8 rows)
+ 
+ SELECT name, lag(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |   8
+  bones     |    
+  churchill |    
+  lassie    |   4
+  mickey    |   7
+  molly     |    
+  rover     |   3
+ (8 rows)
+ 
+ SELECT name, lead(age, 0, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lead 
+ -----------+------
+  ajax      |     
+  alfred    |    8
+  bones     |     
+  churchill |     
+  lassie    |    4
+  mickey    |    7
+  molly     |     
+  rover     |    3
+ (8 rows)
+ 
+ SELECT name, lag(age, 0, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+    name    | lag 
+ -----------+-----
+  ajax      |    
+  alfred    |   8
+  bones     |    
+  churchill |    
+  lassie    |   4
+  mickey    |   7
+  molly     |    
+  rover     |   3
+ (8 rows)
+ 
+ DROP TABLE dogs CASCADE;
+ NOTICE:  drop cascades to view v_dogs
+ DROP FUNCTION volatile_int(INT);
*** a/src/test/regress/sql/window.sql
--- b/src/test/regress/sql/window.sql
***************
*** 641,643 **** SELECT to_char(SUM(n::float8) OVER (ORDER BY i ROWS BETWEEN CURRENT ROW AND 1 FO
--- 641,732 ----
  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);
+ 
+ -- check we haven't reserved words that might break backwards-compatibility:
+ CREATE TABLE reserved (
+   ignore text,
+   respect text,
+   nulls text
+ );
+ DROP TABLE reserved;
+ 
+ -- testing ignore nulls functionality
+ 
+ CREATE TEMPORARY TABLE dogs (
+     name text,
+     breed text,
+     age int
+ );
+ 
+ INSERT INTO dogs VALUES
+ ('ajax',          'mythological', NULL),
+ ('alfred',          NULL,    8),
+ ('bones',     'shar pei', NULL),
+ ('churchill',  'bulldog', NULL),
+ ('lassie',          NULL,    4),
+ ('mickey',      'poodle',    7),
+ ('molly',       'poodle', NULL),
+ ('rover',     'shar pei',    3);
+ 
+ -- test view definitions are preserved
+ CREATE TEMP VIEW v_dogs AS
+   SELECT
+     name,
+     sum(age) OVER (order by age rows between 1 preceding and 1 following) as sum_rows,
+     lag(age, 1) IGNORE NULLS OVER (ORDER BY name DESC) AS lagged_by_1,
+     lag(age, 2) IGNORE NULLS OVER w AS lagged_by_2
+   FROM dogs
+   WINDOW w as (ORDER BY name ASC);
+ SELECT pg_get_viewdef('v_dogs');
+ 
+ CREATE FUNCTION volatile_int(INT) RETURNS INT AS
+   $$ BEGIN RETURN $1; END; $$
+   LANGUAGE PLPGSQL VOLATILE;
+ 
+ -- (1) lags by constant
+ SELECT name, lag(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (2) leads by constant
+ SELECT name, lead(age) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (3) lags by expression
+ SELECT name, lag(age * 2, volatile_int(1)) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age * 2, volatile_int(1)) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age * 2, volatile_int(1)) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (4) leads by expression
+ SELECT name, lead(age * 2, volatile_int(1)) OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age * 2, volatile_int(1)) RESPECT NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age * 2, volatile_int(1)) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- (4) defaults
+ SELECT name, lead(age, 1, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, 2, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, 3, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, volatile_int(1), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, volatile_int(2), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, volatile_int(3), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ SELECT name, lag(age, 1, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, 2, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, 3, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, volatile_int(1), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, volatile_int(2), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, volatile_int(3), -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- these should be errors as the functionality isn't implemented yet:
+ SELECT name, first_value(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, max(age) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ -- ensure that a zero offset still returns the current value, even if NULL
+ SELECT name, lead(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, 0) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lead(age, 0, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ SELECT name, lag(age, 0, -1) IGNORE NULLS OVER (ORDER BY name) FROM dogs ORDER BY name;
+ 
+ DROP TABLE dogs CASCADE;
+ DROP FUNCTION volatile_int(INT);