[PATCH] Add support for ON UPDATE/DELETE actions on ALTER CONSTRAINT

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 03c0b73..204aac9 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7841,6 +7841,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 7c8220c..14166c5 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2900,6 +2900,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 69fd5b2..a28258a 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3529,6 +3529,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 4bd2223..9b4a05f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -184,7 +184,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2279,8 +2280,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3675,7 +3676,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3692,8 +3693,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3707,8 +3708,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3723,8 +3724,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3738,8 +3739,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3757,8 +3758,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3774,7 +3775,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -5381,8 +5383,9 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -5654,8 +5657,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = true;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -16208,7 +16212,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16219,6 +16224,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 07ab1a3..155d0e1 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2097,6 +2097,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index dccc9b2..62a6ff8 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -720,6 +720,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index b904978..16e3717 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -526,6 +526,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index ec6b4c3..4c65c1f 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 03c0b73..1db2936 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7841,8 +7841,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since
+	 * we already have to handle the case of changing to the same action,
+	 * seems simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the
+	 * current action here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -7860,6 +7895,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -7896,23 +7933,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyTriggers and
-			 * CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden bellow
+			 * if the pg_trigger entry is on the referencing table and depending
+			 * on the action used for ON UPDATE/DELETE. But for check triggers
+			 * (in the referenced table) it is kept as is (since ON
+			 * UPDATE/DELETE actions makes no difference for the check
+			 * triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId,
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 7c8220c..14166c5 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2900,6 +2900,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 69fd5b2..a28258a 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3529,6 +3529,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 4bd2223..c718d89 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -184,7 +184,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -537,7 +538,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2270,7 +2272,7 @@ alter_table_cmd:
 					$$ = (Node *)n;
 				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name opt_key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2278,9 +2280,11 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3675,7 +3679,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3692,8 +3696,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3707,8 +3711,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3723,8 +3727,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3738,8 +3742,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3757,8 +3761,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3774,7 +3778,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3854,7 +3859,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3869,6 +3874,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5381,8 +5403,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -5654,8 +5676,8 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = true;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -16208,7 +16230,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16219,6 +16242,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 07ab1a3..ddf42c9 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2080,6 +2080,7 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2097,6 +2098,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index fc3bbe4..076b633 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -1651,3 +1651,127 @@ INSERT INTO fk_notpartitioned_pk VALUES (1600, 601), (1600, 1601);
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2
   FOR VALUES IN (1600);
 -- leave these tables around intentionally
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index d2cecdf..2331b2f 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1230,3 +1230,80 @@ ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2
   FOR VALUES IN (1600);
 
 -- leave these tables around intentionally
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index eb2d33d..87c9342 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7818,6 +7818,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 3961832..d14eaa9 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2899,6 +2899,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 1d78b53..2cc8c3c 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3508,6 +3508,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 90dfac2..71669b9 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -184,7 +184,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2279,8 +2280,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3675,7 +3676,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3692,8 +3693,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3707,8 +3708,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3723,8 +3724,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3738,8 +3739,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3757,8 +3758,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3774,7 +3775,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -5381,8 +5383,9 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -5649,8 +5652,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = true;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -16197,7 +16201,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16208,6 +16213,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index fb9a5c4..ac43800 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2097,6 +2097,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 37440f6..a91a1df 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -720,6 +720,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 22cf4ef..7ab9aec 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -526,6 +526,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index f4745f3..5bf3494 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7496,6 +7496,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 8c8384c..66c817f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2832,6 +2832,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index d8cf660..4127c43 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3428,6 +3428,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 025e82b..11411f0 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -184,7 +184,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2214,8 +2215,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3526,7 +3527,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3542,8 +3543,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $6;
 					processCASbits($7, @7, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3556,8 +3557,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_definition OptConsTableSpace
@@ -3571,8 +3572,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3585,8 +3586,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3603,8 +3604,8 @@ ConstraintElem:
 					n->indexspace		= $7;
 					n->where_clause		= $8;
 					processCASbits($9, @9, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3620,7 +3621,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -5203,8 +5205,9 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = TRUE;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -5471,8 +5474,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = TRUE;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -15799,7 +15803,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -15810,6 +15815,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index aa0b9b0..fd515e9 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2086,6 +2086,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 86127ce..53ceb93 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -663,6 +663,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 519d984..13fea5f 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -476,6 +476,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 424a426..958f7d3 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -6681,6 +6681,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index db492a7..2e0d68b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2592,6 +2592,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 5c03e9f..78fa6fa 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2843,6 +2843,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e27d37c..a6bd48b 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -173,7 +173,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2084,8 +2085,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3200,7 +3201,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3216,8 +3217,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $6;
 					processCASbits($7, @7, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3230,8 +3231,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_definition OptConsTableSpace
@@ -3245,8 +3246,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3259,8 +3260,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3277,8 +3278,8 @@ ConstraintElem:
 					n->indexspace		= $7;
 					n->where_clause		= $8;
 					processCASbits($9, @9, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3294,7 +3295,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -4741,8 +4743,9 @@ CreateTrigStmt:
 					n->whenClause = $14;
 					n->isconstraint  = TRUE;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -4992,8 +4995,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = TRUE;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -14759,7 +14763,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -14770,6 +14775,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 4a19842..2fbce55 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1822,6 +1822,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 6f459df..51b0521 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -654,6 +654,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 358081b..c6844ec 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -473,6 +473,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 567c09a..0f7b964 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -6358,6 +6358,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 823ca3e..794d84d 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2396,6 +2396,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 9c16a1f..1e7d9b6 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -2659,6 +2659,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 030285c..6b6c10c 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -161,7 +161,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2053,8 +2054,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3123,7 +3124,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3139,8 +3140,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $6;
 					processCASbits($7, @7, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3153,8 +3154,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_definition OptConsTableSpace
@@ -3168,8 +3169,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3182,8 +3183,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3200,8 +3201,8 @@ ConstraintElem:
 					n->indexspace		= $7;
 					n->where_clause		= $8;
 					processCASbits($9, @9, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3217,7 +3218,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -4464,8 +4466,9 @@ CreateTrigStmt:
 					n->whenClause = $14;
 					n->isconstraint  = TRUE;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -4717,8 +4720,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = TRUE;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -13872,7 +13876,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -13883,6 +13888,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 3146aa5..f8c1b00 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1626,6 +1626,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index b9f9cf5..7f8f9aa 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -652,6 +652,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 7e29b48..d8d5af1 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -472,6 +472,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 1f7c732..2a308c6 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -6711,6 +6711,26 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Check which deferrable attributes changed. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred)
 	{
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index c2b1ccf..2a530b1 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2627,6 +2627,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index f8d43db..8c39746 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3157,6 +3157,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index a0ef488..0e46adc 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -174,7 +174,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -2097,8 +2098,8 @@ alter_table_cmd:
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3218,7 +3219,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3234,8 +3235,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $6;
 					processCASbits($7, @7, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3248,8 +3249,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_definition OptConsTableSpace
@@ -3263,8 +3264,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3277,8 +3278,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3295,8 +3296,8 @@ ConstraintElem:
 					n->indexspace		= $7;
 					n->where_clause		= $8;
 					processCASbits($9, @9, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3312,7 +3313,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -4791,8 +4793,9 @@ CreateTrigStmt:
 					n->whenClause = $14;
 					n->isconstraint  = TRUE;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -5042,8 +5045,9 @@ CreateAssertStmt:
 					n->args = list_make1($6);
 					n->isconstraint  = TRUE;
 					processCASbits($8, @8, "ASSERTION",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 
 					ereport(ERROR,
 							(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
@@ -14907,7 +14911,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -14918,6 +14923,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 1481fff..0e232fe 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -1830,6 +1830,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index abce3c5..a6e8a5e 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -663,6 +663,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 168d95e..4731037 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -476,6 +476,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index f13a6cd944..5910680cf3 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 3e112b4ef4..86dabc9bbc 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -7843,8 +7843,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since
+	 * we already have to handle the case of changing to the same action,
+	 * seems simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the
+	 * current action here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -7862,6 +7897,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -7898,23 +7935,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyTriggers and
-			 * CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden bellow
+			 * if the pg_trigger entry is on the referencing table and depending
+			 * on the action used for ON UPDATE/DELETE. But for check triggers
+			 * (in the referenced table) it is kept as is (since ON
+			 * UPDATE/DELETE actions makes no difference for the check
+			 * triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId,
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index e8ea59e34a..fa8573dbfa 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2898,6 +2898,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 69731ccdea..1761b81073 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3526,6 +3526,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 6d23bfb0b3..184f1c27eb 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -184,7 +184,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -537,7 +538,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2269,7 +2271,7 @@ alter_table_cmd:
 					$$ = (Node *)n;
 				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name opt_key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2277,9 +2279,11 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3674,7 +3678,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3691,8 +3695,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3706,8 +3710,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3722,8 +3726,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3737,8 +3741,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3756,8 +3760,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3773,7 +3777,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3853,7 +3858,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3868,6 +3873,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5380,8 +5402,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16195,7 +16217,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16206,6 +16229,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index aa4a0dba2a..b541ed3035 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2093,6 +2093,7 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2110,6 +2111,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 68cd3e5676..3948140d46 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -714,6 +714,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index 52164e89d2..dd709462a5 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -1781,3 +1781,127 @@ INSERT INTO fk_notpartitioned_pk VALUES (1600, 601), (1600, 1601);
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2
   FOR VALUES IN (1600);
 -- leave these tables around intentionally
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 6890346637..af898b49fc 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -514,6 +514,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index f387004855..d92ac23737 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1289,3 +1289,80 @@ ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2
   FOR VALUES IN (1600);
 
 -- leave these tables around intentionally
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index e360728c02..b2866f467a 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 515c29072c..56847b90f9 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8305,8 +8305,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since
+	 * we already have to handle the case of changing to the same action,
+	 * seems simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the
+	 * current action here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -8324,6 +8359,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -8360,23 +8397,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyTriggers and
-			 * CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden bellow
+			 * if the pg_trigger entry is on the referencing table and depending
+			 * on the action used for ON UPDATE/DELETE. But for check triggers
+			 * (in the referenced table) it is kept as is (since ON
+			 * UPDATE/DELETE actions makes no difference for the check
+			 * triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId, currcon->oid, 0);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index a8a735c247..f28acf818f 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2900,6 +2900,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 69179a07c3..71492df3b3 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3435,6 +3435,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index e814939a25..f0d68e8e92 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -185,7 +185,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -541,7 +542,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2273,7 +2275,7 @@ alter_table_cmd:
 					$$ = (Node *)n;
 				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name opt_key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2281,9 +2283,11 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3616,7 +3620,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3633,8 +3637,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3648,8 +3652,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3664,8 +3668,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3679,8 +3683,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3698,8 +3702,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3715,7 +3719,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3795,7 +3800,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3810,6 +3815,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5335,8 +5357,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16172,7 +16194,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16183,6 +16206,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index fcfba4be4c..ab8475e22f 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2103,6 +2103,7 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2120,6 +2121,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 2a26aa3a89..cd94101448 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -736,6 +736,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index 401514a3e0..6fa279efe0 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -2019,3 +2019,127 @@ ERROR:  constraint "my_fkey" of relation "fk_part_1_1" does not exist
 drop schema fkpart0, fkpart1, fkpart2 cascade;
 NOTICE:  drop cascades to 8 other objects
 \set VERBOSITY default
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 5bda7febde..dfb792661b 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -528,6 +528,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index beeaf3277d..d6f3bb28e4 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1443,3 +1443,80 @@ alter table fkpart2.fk_part_1_1 drop constraint my_fkey;	-- doesn't exist
 \set VERBOSITY terse	\\ -- suppress cascade details
 drop schema fkpart0, fkpart1, fkpart2 cascade;
 \set VERBOSITY default
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 90bf19564c..198c640b98 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 0f1a9f0e54..b54c3d67c5 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -8979,8 +8979,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since
+	 * we already have to handle the case of changing to the same action,
+	 * seems simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the
+	 * current action here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -8998,6 +9033,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -9034,23 +9071,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyActionTriggers
-			 * and CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden bellow
+			 * if the pg_trigger entry is on the referencing table and depending
+			 * on the action used for ON UPDATE/DELETE. But for check triggers
+			 * (in the referenced table) it is kept as is (since ON
+			 * UPDATE/DELETE actions makes no difference for the check
+			 * triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId, currcon->oid, 0);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 78deade89b..798eac566b 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2906,6 +2906,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 8400dd319e..4bec7ac23d 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3443,6 +3443,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 208b4a1f28..887594982c 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -185,7 +185,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -543,7 +544,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2275,7 +2277,7 @@ alter_table_cmd:
 					$$ = (Node *)n;
 				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name opt_key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2283,9 +2285,11 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3642,7 +3646,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3659,8 +3663,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3674,8 +3678,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3690,8 +3694,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3705,8 +3709,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3724,8 +3728,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3741,7 +3745,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3821,7 +3826,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3836,6 +3841,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5361,8 +5383,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16223,7 +16245,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16234,6 +16257,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+										    | CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 94ded3c135..6cd67fbe13 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2117,6 +2117,7 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2134,6 +2135,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 3578b8009b..149830f8d4 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -736,6 +736,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index 58f6058e70..54dc4d0283 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -2379,3 +2379,128 @@ DROP SCHEMA fkpart7 CASCADE;
 NOTICE:  drop cascades to 2 other objects
 DETAIL:  drop cascades to table fkpart7.pkpart
 drop cascades to table fkpart7.fk
+\set VERBOSITY default
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 99af0b851b..5223142b8f 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -528,6 +528,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index 9c28285717..a878bcbe07 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1667,3 +1667,81 @@ ALTER TABLE fkpart7.pkpart1 ADD PRIMARY KEY (a);
 ALTER TABLE fkpart7.pkpart ADD PRIMARY KEY (a);
 CREATE TABLE fkpart7.fk (a int REFERENCES fkpart7.pkpart);
 DROP SCHEMA fkpart7 CASCADE;
+\set VERBOSITY default
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index 90bf195..198c640 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index fb2be10..f897986 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9012,8 +9012,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since we
+	 * already have to handle the case of changing to the same action, seems
+	 * simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the current action
+	 * here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -9031,6 +9066,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -9067,23 +9104,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyActionTriggers
-			 * and CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden
+			 * bellow if the pg_trigger entry is on the referencing table and
+			 * depending on the action used for ON UPDATE/DELETE. But for
+			 * check triggers (in the referenced table) it is kept as is
+			 * (since ON UPDATE/DELETE actions makes no difference for the
+			 * check triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId, currcon->oid, 0);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 6414ade..5c524e3 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2906,6 +2906,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index 86c31a4..7e4ec65 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3445,6 +3445,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index c97bb36..690f94f 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -185,7 +185,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -543,7 +544,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2275,7 +2277,7 @@ alter_table_cmd:
 					$$ = (Node *)n;
 				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name opt_key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2283,9 +2285,11 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3642,7 +3646,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3659,8 +3663,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3674,8 +3678,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3690,8 +3694,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3705,8 +3709,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3724,8 +3728,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3741,7 +3745,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3821,7 +3826,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3836,6 +3841,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5361,8 +5383,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16218,7 +16240,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16229,6 +16252,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+											| CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 94ded3c..a6d70d4 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2117,6 +2117,8 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER
+										 * CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2134,6 +2136,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set; /* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index e5407bb..32ea16c 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -736,6 +736,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                                      pg_get_constraintdef                                       
+-------------------------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE INITIALLY DEFERRED
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                             pg_get_constraintdef                             
+------------------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE DEFERRABLE
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+                       pg_get_constraintdef                        
+-------------------------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1) ON DELETE CASCADE
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index f0ecf4b..4f226aa 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -2394,3 +2394,127 @@ DROP SCHEMA fkpart8 CASCADE;
 NOTICE:  drop cascades to 2 other objects
 DETAIL:  drop cascades to table fkpart8.tbl1
 drop cascades to table fkpart8.tbl2
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 99af0b8..5223142 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -528,6 +528,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index b67bef0..ae8b235 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1679,3 +1679,80 @@ INSERT INTO fkpart8.tbl2 VALUES(1);
 ALTER TABLE fkpart8.tbl2 DROP CONSTRAINT tbl2_f1_fkey;
 COMMIT;
 DROP SCHEMA fkpart8 CASCADE;
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index cb9b60415d..e22f4f924e 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -55,7 +55,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 05593f3316..689bd8add5 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9007,8 +9007,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since we
+	 * already have to handle the case of changing to the same action, seems
+	 * simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the current action
+	 * here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -9026,6 +9061,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -9062,23 +9099,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyActionTriggers
-			 * and CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden
+			 * bellow if the pg_trigger entry is on the referencing table and
+			 * depending on the action used for ON UPDATE/DELETE. But for
+			 * check triggers (in the referenced table) it is kept as is
+			 * (since ON UPDATE/DELETE actions makes no difference for the
+			 * check triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId, currcon->oid, 0);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index 3432bb921d..58241c1214 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2910,6 +2910,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 18cb014373..584e2e32a0 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2594,6 +2594,8 @@ _equalConstraint(const Constraint *a, const Constraint *b)
 	COMPARE_SCALAR_FIELD(deferrable);
 	COMPARE_SCALAR_FIELD(initdeferred);
 	COMPARE_LOCATION_FIELD(location);
+	COMPARE_SCALAR_FIELD(was_deferrable_set);
+	COMPARE_SCALAR_FIELD(was_initdeferred_set);
 	COMPARE_SCALAR_FIELD(is_no_inherit);
 	COMPARE_NODE_FIELD(raw_expr);
 	COMPARE_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index b0dcd02ff6..dc45f154e3 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3459,6 +3459,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 3f67aaf30e..3cd5579515 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -185,7 +185,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -543,7 +544,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2275,8 +2277,25 @@ alter_table_cmd:
 					n->def = $2;
 					$$ = (Node *)n;
 				}
+			/* ALTER TABLE <name> ALTER CONSTRAINT ... SET */
+			| ALTER CONSTRAINT name SET opt_key_actions ConstraintAttributeSpec
+				{
+					AlterTableCmd *n = makeNode(AlterTableCmd);
+					Constraint *c = makeNode(Constraint);
+					n->subtype = AT_AlterConstraint;
+					n->def = (Node *) c;
+					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
+					c->conname = $3;
+					c->fk_upd_action = (char) ($5 >> 8);
+					c->fk_del_action = (char) ($5 & 0xFF);
+					processCASbits($6, @5, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
+									NULL, NULL, yyscanner);
+					$$ = (Node *)n;
+				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2284,9 +2303,14 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					/* Without SET, always change deferrability */
+					c->was_deferrable_set = true;
+					c->was_initdeferred_set = true;
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, NULL,
+									&c->initdeferred, NULL,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3643,7 +3667,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3660,8 +3684,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3675,8 +3699,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3691,8 +3715,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3706,8 +3730,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3725,8 +3749,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3742,7 +3766,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3822,7 +3847,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3837,6 +3862,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5390,8 +5432,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16247,7 +16289,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16258,6 +16301,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+											| CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index d93a79a554..141dd43df7 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2117,6 +2117,8 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER
+										 * CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2134,6 +2136,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index 23d4265555..8146ad9eb5 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -704,15 +704,15 @@ ORDER BY 1,2,3;
 ---------+------------------------+--------+--------------+----------------
  fkdd    | "RI_FKey_cascade_del"  |      9 | f            | f
  fkdd    | "RI_FKey_noaction_upd" |     17 | t            | t
- fkdd2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fkdd2   | "RI_FKey_noaction_del" |      9 | t            | t
  fkdd2   | "RI_FKey_noaction_upd" |     17 | t            | t
  fkdi    | "RI_FKey_cascade_del"  |      9 | f            | f
  fkdi    | "RI_FKey_noaction_upd" |     17 | t            | f
- fkdi2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fkdi2   | "RI_FKey_noaction_del" |      9 | t            | f
  fkdi2   | "RI_FKey_noaction_upd" |     17 | t            | f
  fknd    | "RI_FKey_cascade_del"  |      9 | f            | f
  fknd    | "RI_FKey_noaction_upd" |     17 | f            | f
- fknd2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fknd2   | "RI_FKey_noaction_del" |      9 | f            | f
  fknd2   | "RI_FKey_noaction_upd" |     17 | f            | f
 (12 rows)
 
@@ -736,6 +736,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index 894084f94f..5792b032b1 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -2394,3 +2394,128 @@ DROP SCHEMA fkpart8 CASCADE;
 NOTICE:  drop cascades to 2 other objects
 DETAIL:  drop cascades to table fkpart8.tbl1
 drop cascades to table fkpart8.tbl2
+\set VERBOSITY default
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey SET ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 99af0b851b..5223142b8f 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -528,6 +528,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index b67bef01df..18cfa1ab16 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1679,3 +1679,81 @@ INSERT INTO fkpart8.tbl2 VALUES(1);
 ALTER TABLE fkpart8.tbl2 DROP CONSTRAINT tbl2_f1_fkey;
 COMMIT;
 DROP SCHEMA fkpart8 CASCADE;
+\set VERBOSITY default
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey SET ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;

diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index e486196477..6a51014b6f 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -56,7 +56,9 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET STORAGE { PLAIN | EXTERNAL | EXTENDED | MAIN }
     ADD <replaceable class="parameter">table_constraint</replaceable> [ NOT VALID ]
     ADD <replaceable class="parameter">table_constraint_using_index</replaceable>
-    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
+    ALTER CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
+      [SET] [ ON DELETE <replaceable class="parameter">action</replaceable> ] [ ON UPDATE <replaceable class="parameter">action</replaceable> ]
+      [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ]
     VALIDATE CONSTRAINT <replaceable class="parameter">constraint_name</replaceable>
     DROP CONSTRAINT [ IF EXISTS ]  <replaceable class="parameter">constraint_name</replaceable> [ RESTRICT | CASCADE ]
     DISABLE TRIGGER [ <replaceable class="parameter">trigger_name</replaceable> | ALL | USER ]
@@ -488,6 +490,14 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       This form alters the attributes of a constraint that was previously
       created. Currently only foreign key constraints may be altered.
      </para>
+     <para>
+      If <literal>SET</literal> keyword is ommitted, the full constraint
+      definition is changed, meaning that every option mentioned is set
+      accordingly and unmentioned options are set as default built-in values,
+      just like <literal>ADD CONSTRAINT</literal> would do, see definition of
+      default values on <xref linkend="sql-createtable"/>. With
+      <literal>SET</literal> keyword, only mentioned attributes are changed.
+     </para>
     </listitem>
    </varlistentry>
 
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index 8e35c5bd1a..70fdea680e 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -9509,8 +9509,43 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
 
+	/*
+	 * Verify for FKCONSTR_ACTION_UNKNOWN, if found, replace by current
+	 * action. We could handle FKCONSTR_ACTION_UNKNOWN bellow, but since we
+	 * already have to handle the case of changing to the same action, seems
+	 * simpler to simple replace FKCONSTR_ACTION_UNKNOWN by the current action
+	 * here.
+	 */
+	if (cmdcon->fk_del_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+	if (cmdcon->fk_upd_action == FKCONSTR_ACTION_UNKNOWN)
+		cmdcon->fk_upd_action = currcon->confupdtype;
+
+	/*
+	 * Do the same for deferrable attributes. But consider that if changed
+	 * only initdeferred attribute and to true, force deferrable to be also
+	 * true. On the other hand, if changed only deferrable attribute and to
+	 * false, force initdeferred to be also false.
+	 */
+	if (!cmdcon->was_deferrable_set)
+		cmdcon->deferrable = cmdcon->initdeferred ? true : currcon->condeferrable;
+
+	if (!cmdcon->was_initdeferred_set)
+		cmdcon->initdeferred = !cmdcon->deferrable ? false : currcon->condeferred;
+
+	/*
+	 * This is a safe check only, should never happen here.
+	 */
+	if (cmdcon->initdeferred && !cmdcon->deferrable)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("constraint declared INITIALLY DEFERRED must be DEFERRABLE")));
+
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->confdeltype != cmdcon->fk_del_action ||
+		currcon->confupdtype != cmdcon->fk_upd_action)
 	{
 		HeapTuple	copyTuple;
 		HeapTuple	tgtuple;
@@ -9528,6 +9563,8 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->confdeltype = cmdcon->fk_del_action;
+		copy_con->confupdtype = cmdcon->fk_upd_action;
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -9564,23 +9601,106 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 				otherrelids = list_append_unique_oid(otherrelids,
 													 tgform->tgrelid);
 
-			/*
-			 * Update deferrability of RI_FKey_noaction_del,
-			 * RI_FKey_noaction_upd, RI_FKey_check_ins and RI_FKey_check_upd
-			 * triggers, but not others; see createForeignKeyActionTriggers
-			 * and CreateFKCheckTrigger.
-			 */
-			if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
-				tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_INS &&
-				tgform->tgfoid != F_RI_FKEY_CHECK_UPD)
-				continue;
-
 			copyTuple = heap_copytuple(tgtuple);
 			copy_tg = (Form_pg_trigger) GETSTRUCT(copyTuple);
 
+			/*
+			 * Set deferrability here, but note that it may be overridden
+			 * bellow if the pg_trigger entry is on the referencing table and
+			 * depending on the action used for ON UPDATE/DELETE. But for
+			 * check triggers (in the referenced table) it is kept as is
+			 * (since ON UPDATE/DELETE actions makes no difference for the
+			 * check triggers).
+			 */
 			copy_tg->tgdeferrable = cmdcon->deferrable;
 			copy_tg->tginitdeferred = cmdcon->initdeferred;
+
+			/*
+			 * Set ON DELETE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL)
+			{
+				switch (cmdcon->fk_del_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_DEL;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_DEL;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_DEL;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_DEL;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_DEL;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_del_action);
+						break;
+				}
+			}
+
+			/*
+			 * Set ON UPDATE action
+			 */
+			if (tgform->tgfoid == F_RI_FKEY_NOACTION_UPD ||
+				tgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+				tgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+				tgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD)
+			{
+				switch (cmdcon->fk_upd_action)
+				{
+					case FKCONSTR_ACTION_NOACTION:
+						copy_tg->tgdeferrable = cmdcon->deferrable;
+						copy_tg->tginitdeferred = cmdcon->initdeferred;
+						copy_tg->tgfoid = F_RI_FKEY_NOACTION_UPD;
+						break;
+					case FKCONSTR_ACTION_RESTRICT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_RESTRICT_UPD;
+						break;
+					case FKCONSTR_ACTION_CASCADE:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_CASCADE_UPD;
+						break;
+					case FKCONSTR_ACTION_SETNULL:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETNULL_UPD;
+						break;
+					case FKCONSTR_ACTION_SETDEFAULT:
+						copy_tg->tgdeferrable = false;
+						copy_tg->tginitdeferred = false;
+						copy_tg->tgfoid = F_RI_FKEY_SETDEFAULT_UPD;
+						break;
+					default:
+						elog(ERROR, "unrecognized FK action type: %d",
+							 (int) cmdcon->fk_upd_action);
+						break;
+				}
+			}
+
 			CatalogTupleUpdate(tgrel, &copyTuple->t_self, copyTuple);
 
 			InvokeObjectPostAlterHook(TriggerRelationId, currcon->oid, 0);
diff --git a/src/backend/nodes/copyfuncs.c b/src/backend/nodes/copyfuncs.c
index eaab97f753..1b15ea2c6a 100644
--- a/src/backend/nodes/copyfuncs.c
+++ b/src/backend/nodes/copyfuncs.c
@@ -2919,6 +2919,8 @@ _copyConstraint(const Constraint *from)
 	COPY_SCALAR_FIELD(deferrable);
 	COPY_SCALAR_FIELD(initdeferred);
 	COPY_LOCATION_FIELD(location);
+	COPY_SCALAR_FIELD(was_deferrable_set);
+	COPY_SCALAR_FIELD(was_initdeferred_set);
 	COPY_SCALAR_FIELD(is_no_inherit);
 	COPY_NODE_FIELD(raw_expr);
 	COPY_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/equalfuncs.c b/src/backend/nodes/equalfuncs.c
index 88b912977e..5dc4fd15b7 100644
--- a/src/backend/nodes/equalfuncs.c
+++ b/src/backend/nodes/equalfuncs.c
@@ -2610,6 +2610,8 @@ _equalConstraint(const Constraint *a, const Constraint *b)
 	COMPARE_SCALAR_FIELD(deferrable);
 	COMPARE_SCALAR_FIELD(initdeferred);
 	COMPARE_LOCATION_FIELD(location);
+	COMPARE_SCALAR_FIELD(was_deferrable_set);
+	COMPARE_SCALAR_FIELD(was_initdeferred_set);
 	COMPARE_SCALAR_FIELD(is_no_inherit);
 	COMPARE_NODE_FIELD(raw_expr);
 	COMPARE_STRING_FIELD(cooked_expr);
diff --git a/src/backend/nodes/outfuncs.c b/src/backend/nodes/outfuncs.c
index e084c3f069..059d69ed6f 100644
--- a/src/backend/nodes/outfuncs.c
+++ b/src/backend/nodes/outfuncs.c
@@ -3471,6 +3471,8 @@ _outConstraint(StringInfo str, const Constraint *node)
 	WRITE_BOOL_FIELD(deferrable);
 	WRITE_BOOL_FIELD(initdeferred);
 	WRITE_LOCATION_FIELD(location);
+	WRITE_BOOL_FIELD(was_deferrable_set);
+	WRITE_BOOL_FIELD(was_initdeferred_set);
 
 	appendStringInfoString(str, " :contype ");
 	switch (node->contype)
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 7e384f956c..73451ebea5 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -185,7 +185,8 @@ static void SplitColQualList(List *qualList,
 							 List **constraintList, CollateClause **collClause,
 							 core_yyscan_t yyscanner);
 static void processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner);
 static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 
@@ -545,7 +546,8 @@ static Node *makeRecursiveViewSelect(char *relname, List *aliases, Node *query);
 %type <ival>	TableLikeOptionList TableLikeOption
 %type <list>	ColQualList
 %type <node>	ColConstraint ColConstraintElem ConstraintAttr
-%type <ival>	key_actions key_delete key_match key_update key_action
+%type <ival>	key_actions opt_key_actions
+%type <ival>	key_delete key_match key_update key_action
 %type <ival>	ConstraintAttributeSpec ConstraintAttributeElem
 %type <str>		ExistingIndex
 
@@ -2298,8 +2300,25 @@ alter_table_cmd:
 					n->def = $2;
 					$$ = (Node *)n;
 				}
+			/* ALTER TABLE <name> ALTER CONSTRAINT ... SET */
+			| ALTER CONSTRAINT name SET opt_key_actions ConstraintAttributeSpec
+				{
+					AlterTableCmd *n = makeNode(AlterTableCmd);
+					Constraint *c = makeNode(Constraint);
+					n->subtype = AT_AlterConstraint;
+					n->def = (Node *) c;
+					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
+					c->conname = $3;
+					c->fk_upd_action = (char) ($5 >> 8);
+					c->fk_del_action = (char) ($5 & 0xFF);
+					processCASbits($6, @5, "ALTER CONSTRAINT statement",
+									&c->deferrable, &c->was_deferrable_set,
+									&c->initdeferred, &c->was_initdeferred_set,
+									NULL, NULL, yyscanner);
+					$$ = (Node *)n;
+				}
 			/* ALTER TABLE <name> ALTER CONSTRAINT ... */
-			| ALTER CONSTRAINT name ConstraintAttributeSpec
+			| ALTER CONSTRAINT name key_actions ConstraintAttributeSpec
 				{
 					AlterTableCmd *n = makeNode(AlterTableCmd);
 					Constraint *c = makeNode(Constraint);
@@ -2307,9 +2326,14 @@ alter_table_cmd:
 					n->def = (Node *) c;
 					c->contype = CONSTR_FOREIGN; /* others not supported, yet */
 					c->conname = $3;
-					processCASbits($4, @4, "ALTER CONSTRAINT statement",
-									&c->deferrable,
-									&c->initdeferred,
+					c->fk_upd_action = (char) ($4 >> 8);
+					c->fk_del_action = (char) ($4 & 0xFF);
+					/* Without SET, always change deferrability */
+					c->was_deferrable_set = true;
+					c->was_initdeferred_set = true;
+					processCASbits($5, @4, "ALTER CONSTRAINT statement",
+									&c->deferrable, NULL,
+									&c->initdeferred, NULL,
 									NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
@@ -3666,7 +3690,7 @@ ConstraintElem:
 					n->raw_expr = $3;
 					n->cooked_expr = NULL;
 					processCASbits($5, @5, "CHECK",
-								   NULL, NULL, &n->skip_validation,
+								   NULL, NULL, NULL, NULL, &n->skip_validation,
 								   &n->is_no_inherit, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *)n;
@@ -3683,8 +3707,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $7;
 					processCASbits($8, @8, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| UNIQUE ExistingIndex ConstraintAttributeSpec
@@ -3698,8 +3722,8 @@ ConstraintElem:
 					n->indexname = $2;
 					n->indexspace = NULL;
 					processCASbits($3, @3, "UNIQUE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY '(' columnList ')' opt_c_include opt_definition OptConsTableSpace
@@ -3714,8 +3738,8 @@ ConstraintElem:
 					n->indexname = NULL;
 					n->indexspace = $8;
 					processCASbits($9, @9, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| PRIMARY KEY ExistingIndex ConstraintAttributeSpec
@@ -3729,8 +3753,8 @@ ConstraintElem:
 					n->indexname = $3;
 					n->indexspace = NULL;
 					processCASbits($4, @4, "PRIMARY KEY",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| EXCLUDE access_method_clause '(' ExclusionConstraintList ')'
@@ -3748,8 +3772,8 @@ ConstraintElem:
 					n->indexspace		= $8;
 					n->where_clause		= $9;
 					processCASbits($10, @10, "EXCLUDE",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					$$ = (Node *)n;
 				}
 			| FOREIGN KEY '(' columnList ')' REFERENCES qualified_name
@@ -3765,7 +3789,8 @@ ConstraintElem:
 					n->fk_upd_action	= (char) ($10 >> 8);
 					n->fk_del_action	= (char) ($10 & 0xFF);
 					processCASbits($11, @11, "FOREIGN KEY",
-								   &n->deferrable, &n->initdeferred,
+								   &n->deferrable, NULL,
+								   &n->initdeferred, NULL,
 								   &n->skip_validation, NULL,
 								   yyscanner);
 					n->initially_valid = !n->skip_validation;
@@ -3845,7 +3870,7 @@ ExclusionWhereClause:
  * We combine the update and delete actions into one value temporarily
  * for simplicity of parsing, and then break them down again in the
  * calling production.  update is in the left 8 bits, delete in the right.
- * Note that NOACTION is the default.
+ * Note that NOACTION is the default. See also opt_key_actions.
  */
 key_actions:
 			key_update
@@ -3860,6 +3885,23 @@ key_actions:
 				{ $$ = (FKCONSTR_ACTION_NOACTION << 8) | (FKCONSTR_ACTION_NOACTION & 0xFF); }
 		;
 
+/*
+ * Basically the same as key_actions, but using FKCONSTR_ACTION_UNKNOWN
+ * as the default one instead of NOACTION.
+ */
+opt_key_actions:
+			key_update
+				{ $$ = ($1 << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+			| key_delete
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | ($1 & 0xFF); }
+			| key_update key_delete
+				{ $$ = ($1 << 8) | ($2 & 0xFF); }
+			| key_delete key_update
+				{ $$ = ($2 << 8) | ($1 & 0xFF); }
+			| /*EMPTY*/
+				{ $$ = (FKCONSTR_ACTION_UNKNOWN << 8) | (FKCONSTR_ACTION_UNKNOWN & 0xFF); }
+		;
+
 key_update: ON UPDATE key_action		{ $$ = $3; }
 		;
 
@@ -5419,8 +5461,8 @@ CreateTrigStmt:
 					n->transitionRels = NIL;
 					n->isconstraint  = true;
 					processCASbits($10, @10, "TRIGGER",
-								   &n->deferrable, &n->initdeferred, NULL,
-								   NULL, yyscanner);
+								   &n->deferrable, NULL, &n->initdeferred, NULL,
+								   NULL, NULL, yyscanner);
 					n->constrrel = $9;
 					$$ = (Node *)n;
 				}
@@ -16357,7 +16399,8 @@ SplitColQualList(List *qualList,
  */
 static void
 processCASbits(int cas_bits, int location, const char *constrType,
-			   bool *deferrable, bool *initdeferred, bool *not_valid,
+			   bool *deferrable, bool *was_deferrable_set,
+			   bool *initdeferred, bool *was_initdeferred_set, bool *not_valid,
 			   bool *no_inherit, core_yyscan_t yyscanner)
 {
 	/* defaults */
@@ -16368,6 +16411,14 @@ processCASbits(int cas_bits, int location, const char *constrType,
 	if (not_valid)
 		*not_valid = false;
 
+	if (was_deferrable_set)
+		*was_deferrable_set = cas_bits & (CAS_DEFERRABLE
+										  | CAS_NOT_DEFERRABLE) ? true : false;
+
+	if (was_initdeferred_set)
+		*was_initdeferred_set = cas_bits & (CAS_INITIALLY_DEFERRED
+											| CAS_INITIALLY_IMMEDIATE) ? true : false;
+
 	if (cas_bits & (CAS_DEFERRABLE | CAS_INITIALLY_DEFERRED))
 	{
 		if (deferrable)
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 2039b42449..e685d2ba0b 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -2137,6 +2137,8 @@ typedef enum ConstrType			/* types of constraints */
 #define FKCONSTR_ACTION_CASCADE		'c'
 #define FKCONSTR_ACTION_SETNULL		'n'
 #define FKCONSTR_ACTION_SETDEFAULT	'd'
+#define FKCONSTR_ACTION_UNKNOWN		'u' /* unknown is used only for ALTER
+										 * CONSTRAINT */
 
 /* Foreign key matchtype codes */
 #define FKCONSTR_MATCH_FULL			'f'
@@ -2154,6 +2156,10 @@ typedef struct Constraint
 	bool		initdeferred;	/* INITIALLY DEFERRED? */
 	int			location;		/* token location, or -1 if unknown */
 
+	/* Fields used by ALTER CONSTRAINT to verify if a change was actually made */
+	bool		was_deferrable_set;		/* Was DEFERRABLE informed? */
+	bool		was_initdeferred_set;	/* Was INITIALLY DEFERRED informed? */
+
 	/* Fields used for constraints with expressions (CHECK and DEFAULT): */
 	bool		is_no_inherit;	/* is constraint non-inheritable? */
 	Node	   *raw_expr;		/* expr, as untransformed parse tree */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
index fb6d86a269..e67e1953aa 100644
--- a/src/test/regress/expected/alter_table.out
+++ b/src/test/regress/expected/alter_table.out
@@ -704,15 +704,15 @@ ORDER BY 1,2,3;
 ---------+------------------------+--------+--------------+----------------
  fkdd    | "RI_FKey_cascade_del"  |      9 | f            | f
  fkdd    | "RI_FKey_noaction_upd" |     17 | t            | t
- fkdd2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fkdd2   | "RI_FKey_noaction_del" |      9 | t            | t
  fkdd2   | "RI_FKey_noaction_upd" |     17 | t            | t
  fkdi    | "RI_FKey_cascade_del"  |      9 | f            | f
  fkdi    | "RI_FKey_noaction_upd" |     17 | t            | f
- fkdi2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fkdi2   | "RI_FKey_noaction_del" |      9 | t            | f
  fkdi2   | "RI_FKey_noaction_upd" |     17 | t            | f
  fknd    | "RI_FKey_cascade_del"  |      9 | f            | f
  fknd    | "RI_FKey_noaction_upd" |     17 | f            | f
- fknd2   | "RI_FKey_cascade_del"  |      9 | f            | f
+ fknd2   | "RI_FKey_noaction_del" |      9 | f            | f
  fknd2   | "RI_FKey_noaction_upd" |     17 | f            | f
 (12 rows)
 
@@ -736,6 +736,28 @@ ORDER BY 1,2,3;
  fknd2   | "RI_FKey_check_upd" |     17 | f            | f
 (12 rows)
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+              pg_get_constraintdef               
+-------------------------------------------------
+ FOREIGN KEY (ftest1) REFERENCES pktable(ptest1)
+(1 row)
+
 -- temp tables should go away by themselves, need not drop them.
 -- test check constraint adding
 create table atacc1 ( test int );
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index 07bd5b6434..dcab082d69 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -2470,3 +2470,128 @@ DROP SCHEMA fkpart9 CASCADE;
 NOTICE:  drop cascades to 2 other objects
 DETAIL:  drop cascades to table fkpart9.pk
 drop cascades to table fkpart9.fk
+\set VERBOSITY default
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey SET ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+INFO:  ON UPDATE from NO ACTION to NO ACTION: OK.
+INFO:  ON UPDATE from RESTRICT to NO ACTION: OK.
+INFO:  ON UPDATE from CASCADE to NO ACTION: OK.
+INFO:  ON UPDATE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON UPDATE from SET NULL to NO ACTION: OK.
+INFO:  ON DELETE from NO ACTION to NO ACTION: OK.
+INFO:  ON DELETE from RESTRICT to NO ACTION: OK.
+INFO:  ON DELETE from CASCADE to NO ACTION: OK.
+INFO:  ON DELETE from SET DEFAULT to NO ACTION: OK.
+INFO:  ON DELETE from SET NULL to NO ACTION: OK.
+INFO:  ON UPDATE from NO ACTION to RESTRICT: OK.
+INFO:  ON UPDATE from RESTRICT to RESTRICT: OK.
+INFO:  ON UPDATE from CASCADE to RESTRICT: OK.
+INFO:  ON UPDATE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON UPDATE from SET NULL to RESTRICT: OK.
+INFO:  ON DELETE from NO ACTION to RESTRICT: OK.
+INFO:  ON DELETE from RESTRICT to RESTRICT: OK.
+INFO:  ON DELETE from CASCADE to RESTRICT: OK.
+INFO:  ON DELETE from SET DEFAULT to RESTRICT: OK.
+INFO:  ON DELETE from SET NULL to RESTRICT: OK.
+INFO:  ON UPDATE from NO ACTION to CASCADE: OK.
+INFO:  ON UPDATE from RESTRICT to CASCADE: OK.
+INFO:  ON UPDATE from CASCADE to CASCADE: OK.
+INFO:  ON UPDATE from SET DEFAULT to CASCADE: OK.
+INFO:  ON UPDATE from SET NULL to CASCADE: OK.
+INFO:  ON DELETE from NO ACTION to CASCADE: OK.
+INFO:  ON DELETE from RESTRICT to CASCADE: OK.
+INFO:  ON DELETE from CASCADE to CASCADE: OK.
+INFO:  ON DELETE from SET DEFAULT to CASCADE: OK.
+INFO:  ON DELETE from SET NULL to CASCADE: OK.
+INFO:  ON UPDATE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON UPDATE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON UPDATE from CASCADE to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON UPDATE from SET NULL to SET DEFAULT: OK.
+INFO:  ON DELETE from NO ACTION to SET DEFAULT: OK.
+INFO:  ON DELETE from RESTRICT to SET DEFAULT: OK.
+INFO:  ON DELETE from CASCADE to SET DEFAULT: OK.
+INFO:  ON DELETE from SET DEFAULT to SET DEFAULT: OK.
+INFO:  ON DELETE from SET NULL to SET DEFAULT: OK.
+INFO:  ON UPDATE from NO ACTION to SET NULL: OK.
+INFO:  ON UPDATE from RESTRICT to SET NULL: OK.
+INFO:  ON UPDATE from CASCADE to SET NULL: OK.
+INFO:  ON UPDATE from SET DEFAULT to SET NULL: OK.
+INFO:  ON UPDATE from SET NULL to SET NULL: OK.
+INFO:  ON DELETE from NO ACTION to SET NULL: OK.
+INFO:  ON DELETE from RESTRICT to SET NULL: OK.
+INFO:  ON DELETE from CASCADE to SET NULL: OK.
+INFO:  ON DELETE from SET DEFAULT to SET NULL: OK.
+INFO:  ON DELETE from SET NULL to SET NULL: OK.
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
index 3801f19c58..590ff7e43b 100644
--- a/src/test/regress/sql/alter_table.sql
+++ b/src/test/regress/sql/alter_table.sql
@@ -528,6 +528,16 @@ FROM pg_trigger JOIN pg_constraint con ON con.oid = tgconstraint
 WHERE tgrelid = 'fktable'::regclass
 ORDER BY 1,2,3;
 
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 INITIALLY IMMEDIATE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
+ALTER TABLE FKTABLE ALTER CONSTRAINT fkdi2 NOT DEFERRABLE;
+SELECT pg_get_constraintdef(oid) FROM pg_constraint WHERE conrelid = 'fktable'::regclass AND conname = 'fkdi2';
+
 -- temp tables should go away by themselves, need not drop them.
 
 -- test check constraint adding
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index c5c9011afc..73a586131f 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -1738,3 +1738,81 @@ DELETE FROM fkpart9.pk WHERE a=35;
 SELECT * FROM fkpart9.pk;
 SELECT * FROM fkpart9.fk;
 DROP SCHEMA fkpart9 CASCADE;
+\set VERBOSITY default
+
+-- ALTER CONSTRAINT changing ON UPDATE/DELETE.
+-- Try all combinations and validate the diff with a created constraint
+CREATE SCHEMA createtest; -- created constraints with target action, validation
+CREATE SCHEMA altertest;  -- created with source and altered to target, test
+
+DO
+$test_alter_con$
+DECLARE
+    v_result json;
+    method text;
+    from_action text;
+    to_action text;
+BEGIN
+    FOR method, from_action, to_action IN
+        WITH act(action) AS (
+            SELECT unnest('{NO ACTION,RESTRICT,CASCADE,SET DEFAULT,SET NULL}'::text[])
+        )
+        SELECT
+            m.method, a1.action, a2.action
+        FROM unnest('{UPDATE,DELETE}'::text[]) AS m(method), act a1, act a2
+    LOOP
+        EXECUTE format(
+            $sql$
+                 -- Alter from ON %1$s %2$s to ON %1$s %3$s
+                CREATE TABLE createtest.foo(id integer primary key);
+                CREATE TABLE createtest.bar(foo_id integer DEFAULT 0 REFERENCES createtest.foo ON %1$s %3$s, val text);
+
+                CREATE TABLE altertest.foo(id integer primary key);
+                INSERT INTO altertest.foo VALUES(0),(1),(2),(3);
+
+                CREATE TABLE altertest.bar(foo_id integer DEFAULT 0 REFERENCES altertest.foo ON %1$s %2$s, val text);
+
+                ALTER TABLE altertest.bar ALTER CONSTRAINT bar_foo_id_fkey SET ON %1$s %3$s;
+
+            $sql$, method, from_action, to_action);
+
+        SELECT json_agg(t)
+        INTO v_result
+        FROM (
+            -- Do EXCEPT of the "altertest" and "createtest" constraints, if they are equal (as expected), it should return empty
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('altertest.foo'::regclass, 'altertest.bar'::regclass)
+            EXCEPT
+            SELECT
+                rel.relname, replace(tg.tgname, tg.oid::text, 'OID') AS tgname,
+                tg.tgfoid::regproc, con.conname, con.confupdtype, con.confdeltype, tg.tgdeferrable,
+                regexp_replace(pg_get_constraintdef(con.oid), '(createtest\.|altertest\.)', '') AS condef
+            FROM pg_trigger tg
+                JOIN pg_constraint con ON con.oid = tg.tgconstraint
+                JOIN pg_class rel ON tg.tgrelid = rel.oid
+            WHERE tg.tgrelid IN ('createtest.foo'::regclass, 'createtest.bar'::regclass)
+        ) t;
+
+        DROP TABLE createtest.bar;
+        DROP TABLE createtest.foo;
+        DROP TABLE altertest.bar;
+        DROP TABLE altertest.foo;
+
+        IF (v_result IS NULL) THEN
+            RAISE INFO 'ON % from % to %: OK.', method, from_action, to_action;
+        ELSE
+            RAISE EXCEPTION 'ON % from % to %. FAILED! Unmatching rows: %', method, from_action, to_action, v_result;
+        END IF;
+    END LOOP;
+END;
+$test_alter_con$
+;
+
+DROP SCHEMA createtest;
+DROP SCHEMA altertest;