v9-0005-Add-support-for-NOT-ENFORCED-in-foreign-key-const.patch

From e8e10fbe72c093cf6991c98ca376a385b154b52b Mon Sep 17 00:00:00 2001
From: Amul Sul <amul.sul@enterprisedb.com>
Date: Wed, 15 Jan 2025 17:19:02 +0530
Subject: [PATCH v9 5/6] Add support for NOT ENFORCED in foreign key
 constraints.

Typically, when a foreign key (FK) constraint is created on a table,
action and check triggers are added to maintain data integrity.  With
this patch, if a constraint is marked as NOT ENFORCED, integrity
checks are no longer required, making these triggers unnecessary.
Consequently, when creating a NOT ENFORCED FK constraint, triggers
will not be created, and the constraint will be marked as NOT VALID.
Similarly, if an existing FK constraint is changed to NOT ENFORCED,
the associated triggers will be dropped, and the constraint will also
be marked as NOT VALID. Conversely, if a NOT ENFORCED FK constraint is
changed to ENFORCED, the necessary triggers will be created, and the
constraint will remain in the NOT VALID state.

----
NOTE: In this patch, the tryAttachPartitionForeignKey() function will
not merge the constraint if the enforcibility differs. This will be
addressed in the next patch.
----
---
 doc/src/sgml/advanced.sgml                |  13 +
 doc/src/sgml/catalogs.sgml                |   2 +-
 doc/src/sgml/ddl.sgml                     |  12 +-
 doc/src/sgml/ref/alter_table.sgml         |  12 +-
 doc/src/sgml/ref/create_table.sgml        |   2 +-
 src/backend/catalog/pg_constraint.c       |   5 +-
 src/backend/catalog/sql_features.txt      |   2 +-
 src/backend/commands/tablecmds.c          | 398 ++++++++++++++++------
 src/backend/parser/gram.y                 |   7 +-
 src/backend/parser/parse_utilcmd.c        |  14 +-
 src/backend/utils/cache/relcache.c        |   1 +
 src/include/utils/rel.h                   |   3 +
 src/test/regress/expected/constraints.out |   8 +-
 src/test/regress/expected/foreign_key.out | 130 ++++++-
 src/test/regress/sql/foreign_key.sql      |  93 ++++-
 15 files changed, 568 insertions(+), 134 deletions(-)

diff --git a/doc/src/sgml/advanced.sgml b/doc/src/sgml/advanced.sgml
index 755c9f14850..b7d90de69d7 100644
--- a/doc/src/sgml/advanced.sgml
+++ b/doc/src/sgml/advanced.sgml
@@ -125,6 +125,19 @@ ERROR:  insert or update on table "weather" violates foreign key constraint "wea
 DETAIL:  Key (city)=(Berkeley) is not present in table "cities".
 </screen>
    </para>
+   <para>
+    If, for some reason, you do not want to enforce this constraint and wish to
+    avoid the error, you can modify the foreign key constraint to <literal>NOT ENFORCED</literal>,
+    or specify it in the <link linkend="sql-createtable"><command>CREATE TABLE</command></link>.
+   </para>
+   <para>
+    Let's change the constraint to <literal>NOT ENFORCED</literal>, and when you
+    attempt to reinsert the same record, it will not result in any error.
+<programlisting>
+ALTER TABLE weather ALTER CONSTRAINT weather_city_fkey NOT ENFORCED;
+INSERT INTO weather VALUES ('Berkeley', 45, 53, 0.0, '1994-11-28');
+</programlisting>
+   </para>
 
    <para>
     The behavior of foreign keys can be finely tuned to your
diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index d3036c5ba9d..72b68cb8d2d 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -2597,7 +2597,7 @@ SCRAM-SHA-256$<replaceable>&lt;iteration count&gt;</replaceable>:<replaceable>&l
       </para>
       <para>
        Is the constraint enforced?
-       Currently, can be false only for CHECK constraints
+       Currently, can be false only for foreign keys and CHECK constraints
       </para></entry>
      </row>
 
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index dea04d64db6..d3377503981 100644
--- a/doc/src/sgml/ddl.sgml
+++ b/doc/src/sgml/ddl.sgml
@@ -1054,11 +1054,13 @@ CREATE TABLE example (
    </indexterm>
 
    <para>
-    A foreign key constraint specifies that the values in a column (or
-    a group of columns) must match the values appearing in some row
-    of another table.
-    We say this maintains the <firstterm>referential
-    integrity</firstterm> between two related tables.
+    A foreign key constraint with <literal>ENFORCED</literal>, the default
+    setting, specifies that the values in a column (or a group of columns)
+    must match the values appearing in some row of another table.  We say this
+    maintains the <firstterm>referential integrity</firstterm> between two
+    related tables.  If a foreign key constraint is created with <literal>NOT ENFORCED</literal>,
+    the check for aforementioned <firstterm>referential integrity</firstterm>
+    will not be performed.
    </para>
 
    <para>
diff --git a/doc/src/sgml/ref/alter_table.sgml b/doc/src/sgml/ref/alter_table.sgml
index f9576da435e..8d4d0dec9d2 100644
--- a/doc/src/sgml/ref/alter_table.sgml
+++ b/doc/src/sgml/ref/alter_table.sgml
@@ -58,7 +58,7 @@ ALTER TABLE [ IF EXISTS ] <replaceable class="parameter">name</replaceable>
     ALTER [ COLUMN ] <replaceable class="parameter">column_name</replaceable> SET COMPRESSION <replaceable class="parameter">compression_method</replaceable>
     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> [ DEFERRABLE | NOT DEFERRABLE ] [ INITIALLY DEFERRED | INITIALLY IMMEDIATE ] [ ENFORCED | NOT ENFORCED ]
     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 ]
@@ -553,6 +553,13 @@ 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>
+      Note that when a constraint is changed to <literal>NOT ENFORCED</literal>,
+      it is also marked as <literal>NOT VALID</literal>.  While this might seem
+      unnecessary, it is done for consistency and should be set accordingly.
+      This ensures that if the constraint is later changed to <literal>ENFORCED</literal>,
+      it will automatically be in the correct <literal>NOT VALID</literal> state.
+     </para>
     </listitem>
    </varlistentry>
 
@@ -563,7 +570,8 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
       This form validates a foreign key or check constraint that was
       previously created as <literal>NOT VALID</literal>, by scanning the
       table to ensure there are no rows for which the constraint is not
-      satisfied.  Nothing happens if the constraint is already marked valid.
+      satisfied.  If the constraint is not enforced, an error is thrown.
+      Nothing happens if the constraint is already marked valid.
       (See <xref linkend="sql-altertable-notes"/> below for an explanation
       of the usefulness of this command.)
      </para>
diff --git a/doc/src/sgml/ref/create_table.sgml b/doc/src/sgml/ref/create_table.sgml
index 2237321cb4f..5071dfeabf9 100644
--- a/doc/src/sgml/ref/create_table.sgml
+++ b/doc/src/sgml/ref/create_table.sgml
@@ -1401,7 +1401,7 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
      </para>
 
      <para>
-      This is currently only supported for <literal>CHECK</literal>
+      This is currently only supported for foreign key and <literal>CHECK</literal>
       constraints.
      </para>
     </listitem>
diff --git a/src/backend/catalog/pg_constraint.c b/src/backend/catalog/pg_constraint.c
index bbf4742e18c..1d7b29de40d 100644
--- a/src/backend/catalog/pg_constraint.c
+++ b/src/backend/catalog/pg_constraint.c
@@ -100,8 +100,9 @@ CreateConstraintEntry(const char *constraintName,
 	ObjectAddresses *addrs_auto;
 	ObjectAddresses *addrs_normal;
 
-	/* Only CHECK constraint can be not enforced */
-	Assert(isEnforced || constraintType == CONSTRAINT_CHECK);
+	/* Only CHECK or FOREIGN KEY constraint can be not enforced */
+	Assert(isEnforced || constraintType == CONSTRAINT_CHECK ||
+		   constraintType == CONSTRAINT_FOREIGN);
 	/* NOT ENFORCED constraint must be NOT VALID */
 	Assert(isEnforced || !isValidated);
 
diff --git a/src/backend/catalog/sql_features.txt b/src/backend/catalog/sql_features.txt
index 2f250d2c57b..d49471bbdf2 100644
--- a/src/backend/catalog/sql_features.txt
+++ b/src/backend/catalog/sql_features.txt
@@ -281,7 +281,7 @@ F461	Named character sets			NO
 F471	Scalar subquery values			YES	
 F481	Expanded NULL predicate			YES	
 F491	Constraint management			YES	
-F492	Optional table constraint enforcement			NO	check constraints only
+F492	Optional table constraint enforcement			NO	foreign key and check constraints only
 F501	Features and conformance views			YES	
 F501	Features and conformance views	01	SQL_FEATURES view	YES	
 F501	Features and conformance views	02	SQL_SIZING view	YES	
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
index e4bde88d432..61ff9975af4 100644
--- a/src/backend/commands/tablecmds.c
+++ b/src/backend/commands/tablecmds.c
@@ -391,11 +391,23 @@ static void AlterSeqNamespaces(Relation classRel, Relation rel,
 							   LOCKMODE lockmode);
 static ObjectAddress ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 										   bool recurse, bool recursing, LOCKMODE lockmode);
-static bool ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
-									 const Oid fkrelid, const Oid pkrelid,
-									 HeapTuple contuple, List **otherrelids,
-									 LOCKMODE lockmode);
-static void AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
+static bool ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel,
+									 Relation tgrel, const Oid fkrelid,
+									 const Oid pkrelid, HeapTuple contuple,
+									 List **otherrelids, LOCKMODE lockmode,
+									 Oid ReferencedParentDelTrigger,
+									 Oid ReferencedParentUpdTrigger,
+									 Oid ReferencingParentInsTrigger,
+									 Oid ReferencingParentUpdTrigger);
+static void ATExecAlterConstrEnforceability(Constraint *cmdcon, Relation conrel,
+											Relation tgrel, const Oid fkrelid,
+											const Oid pkrelid, HeapTuple contuple,
+											List **otherrelids, LOCKMODE lockmode,
+											Oid ReferencedParentDelTrigger,
+											Oid ReferencedParentUpdTrigger,
+											Oid ReferencingParentInsTrigger,
+											Oid ReferencingParentUpdTrigger);
+static void AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Oid fkrel,
 											bool deferrable, bool initdeferred,
 											List **otherrelids);
 static void ATExecAlterChildConstr(Constraint *cmdcon, Relation conrel, Relation tgrel,
@@ -10455,7 +10467,7 @@ addFkConstraint(addFkConstraintSides fkside,
 									  CONSTRAINT_FOREIGN,
 									  fkconstraint->deferrable,
 									  fkconstraint->initdeferred,
-									  true, /* Is Enforced */
+									  fkconstraint->is_enforced,
 									  fkconstraint->initially_valid,
 									  parentConstr,
 									  RelationGetRelid(rel),
@@ -10573,20 +10585,22 @@ addFkRecurseReferenced(Constraint *fkconstraint, Relation rel,
 					   Oid parentDelTrigger, Oid parentUpdTrigger,
 					   bool with_period)
 {
-	Oid			deleteTriggerOid,
-				updateTriggerOid;
+	Oid			deleteTriggerOid = InvalidOid,
+				updateTriggerOid = InvalidOid;
 
 	Assert(CheckRelationLockedByMe(pkrel, ShareRowExclusiveLock, true));
 	Assert(CheckRelationLockedByMe(rel, ShareRowExclusiveLock, true));
 
 	/*
-	 * Create the action triggers that enforce the constraint.
+	 * Create action triggers to enforce the constraint, or skip them if the
+	 * constraint is not enforced.
 	 */
-	createForeignKeyActionTriggers(rel, RelationGetRelid(pkrel),
-								   fkconstraint,
-								   parentConstr, indexOid,
-								   parentDelTrigger, parentUpdTrigger,
-								   &deleteTriggerOid, &updateTriggerOid);
+	if (fkconstraint->is_enforced)
+		createForeignKeyActionTriggers(rel, RelationGetRelid(pkrel),
+									   fkconstraint,
+									   parentConstr, indexOid,
+									   parentDelTrigger, parentUpdTrigger,
+									   &deleteTriggerOid, &updateTriggerOid);
 
 	/*
 	 * If the referenced table is partitioned, recurse on ourselves to handle
@@ -10707,8 +10721,8 @@ addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
 						Oid parentInsTrigger, Oid parentUpdTrigger,
 						bool with_period)
 {
-	Oid			insertTriggerOid,
-				updateTriggerOid;
+	Oid			insertTriggerOid = InvalidOid,
+				updateTriggerOid = InvalidOid;
 
 	Assert(OidIsValid(parentConstr));
 	Assert(CheckRelationLockedByMe(rel, ShareRowExclusiveLock, true));
@@ -10720,29 +10734,32 @@ addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
 				 errmsg("foreign key constraints are not supported on foreign tables")));
 
 	/*
-	 * Add the check triggers to it and, if necessary, schedule it to be
-	 * checked in Phase 3.
+	 * Add check triggers if the constraint is enforced, and if needed,
+	 * schedule them to be checked in Phase 3.
 	 *
 	 * If the relation is partitioned, drill down to do it to its partitions.
 	 */
-	createForeignKeyCheckTriggers(RelationGetRelid(rel),
-								  RelationGetRelid(pkrel),
-								  fkconstraint,
-								  parentConstr,
-								  indexOid,
-								  parentInsTrigger, parentUpdTrigger,
-								  &insertTriggerOid, &updateTriggerOid);
+	if (fkconstraint->is_enforced)
+		createForeignKeyCheckTriggers(RelationGetRelid(rel),
+									  RelationGetRelid(pkrel),
+									  fkconstraint,
+									  parentConstr,
+									  indexOid,
+									  parentInsTrigger, parentUpdTrigger,
+									  &insertTriggerOid, &updateTriggerOid);
 
 	if (rel->rd_rel->relkind == RELKIND_RELATION)
 	{
 		/*
 		 * Tell Phase 3 to check that the constraint is satisfied by existing
-		 * rows. We can skip this during table creation, when requested
-		 * explicitly by specifying NOT VALID in an ADD FOREIGN KEY command,
-		 * and when we're recreating a constraint following a SET DATA TYPE
-		 * operation that did not impugn its validity.
+		 * rows. We can skip this during table creation, when constraint is
+		 * specified as NOT ENFORCED, when requested explicitly by specifying
+		 * NOT VALID in an ADD FOREIGN KEY command, and when we're recreating
+		 * a constraint following a SET DATA TYPE operation that did not
+		 * impugn its validity.
 		 */
-		if (wqueue && !old_check_ok && !fkconstraint->skip_validation)
+		if (wqueue && !old_check_ok && !fkconstraint->skip_validation &&
+			fkconstraint->is_enforced)
 		{
 			NewConstraint *newcon;
 			AlteredTableInfo *tab;
@@ -10977,8 +10994,8 @@ CloneFkReferenced(Relation parentRel, Relation partitionRel)
 		AttrNumber	confdelsetcols[INDEX_MAX_KEYS];
 		Constraint *fkconstraint;
 		ObjectAddress address;
-		Oid			deleteTriggerOid,
-					updateTriggerOid;
+		Oid			deleteTriggerOid = InvalidOid,
+					updateTriggerOid = InvalidOid;
 
 		tuple = SearchSysCache1(CONSTROID, ObjectIdGetDatum(constrOid));
 		if (!HeapTupleIsValid(tuple))
@@ -11038,8 +11055,9 @@ CloneFkReferenced(Relation parentRel, Relation partitionRel)
 		fkconstraint->fk_del_set_cols = NIL;
 		fkconstraint->old_conpfeqop = NIL;
 		fkconstraint->old_pktable_oid = InvalidOid;
+		fkconstraint->is_enforced = constrForm->conenforced;
 		fkconstraint->skip_validation = false;
-		fkconstraint->initially_valid = true;
+		fkconstraint->initially_valid = constrForm->convalidated;
 
 		/* set up colnames that are used to generate the constraint name */
 		for (int i = 0; i < numfks; i++)
@@ -11067,9 +11085,10 @@ CloneFkReferenced(Relation parentRel, Relation partitionRel)
 		 * parent OIDs for similar triggers that will be created on the
 		 * partition in addFkRecurseReferenced().
 		 */
-		GetForeignKeyActionTriggers(trigrel, constrOid,
-									constrForm->confrelid, constrForm->conrelid,
-									&deleteTriggerOid, &updateTriggerOid);
+		if (constrForm->conenforced)
+			GetForeignKeyActionTriggers(trigrel, constrOid,
+										constrForm->confrelid, constrForm->conrelid,
+										&deleteTriggerOid, &updateTriggerOid);
 
 		/* Add this constraint ... */
 		address = addFkConstraint(addFkReferencedSide,
@@ -11235,17 +11254,18 @@ CloneFkReferencing(List **wqueue, Relation parentRel, Relation partRel)
 			mapped_conkey[i] = attmap->attnums[conkey[i] - 1];
 
 		/*
-		 * Get the "check" triggers belonging to the constraint to pass as
-		 * parent OIDs for similar triggers that will be created on the
-		 * partition in addFkRecurseReferencing().  They are also passed to
-		 * tryAttachPartitionForeignKey() below to simply assign as parents to
-		 * the partition's existing "check" triggers, that is, if the
-		 * corresponding constraints is deemed attachable to the parent
-		 * constraint.
+		 * Get the "check" triggers belonging to the constraint, if it is
+		 * enforced, to pass as parent OIDs for similar triggers that will be
+		 * created on the partition in addFkRecurseReferencing().  They are
+		 * also passed to tryAttachPartitionForeignKey() below to simply
+		 * assign as parents to the partition's existing "check" triggers,
+		 * that is, if the corresponding constraints is deemed attachable to
+		 * the parent constraint.
 		 */
-		GetForeignKeyCheckTriggers(trigrel, constrForm->oid,
-								   constrForm->confrelid, constrForm->conrelid,
-								   &insertTriggerOid, &updateTriggerOid);
+		if (constrForm->conenforced)
+			GetForeignKeyCheckTriggers(trigrel, constrForm->oid,
+									   constrForm->confrelid, constrForm->conrelid,
+									   &insertTriggerOid, &updateTriggerOid);
 
 		/*
 		 * Before creating a new constraint, see whether any existing FKs are
@@ -11298,6 +11318,7 @@ CloneFkReferencing(List **wqueue, Relation parentRel, Relation partRel)
 		fkconstraint->fk_del_set_cols = NIL;
 		fkconstraint->old_conpfeqop = NIL;
 		fkconstraint->old_pktable_oid = InvalidOid;
+		fkconstraint->is_enforced = constrForm->conenforced;
 		fkconstraint->skip_validation = false;
 		fkconstraint->initially_valid = constrForm->convalidated;
 		for (int i = 0; i < numfks; i++)
@@ -11421,6 +11442,7 @@ tryAttachPartitionForeignKey(List **wqueue,
 	if (OidIsValid(partConstr->conparentid) ||
 		partConstr->condeferrable != parentConstr->condeferrable ||
 		partConstr->condeferred != parentConstr->condeferred ||
+		partConstr->conenforced != parentConstr->conenforced ||
 		partConstr->confupdtype != parentConstr->confupdtype ||
 		partConstr->confdeltype != parentConstr->confdeltype ||
 		partConstr->confmatchtype != parentConstr->confmatchtype)
@@ -11463,6 +11485,7 @@ AttachPartitionForeignKey(List **wqueue,
 	Form_pg_constraint partConstr;
 	Oid			partConstrFrelid;
 	Oid			partConstrRelid;
+	bool		parentConstrIsEnforced;
 	bool		parentConstrIsValid;
 	bool		partConstrIsValid;
 	Oid			insertTriggerOid,
@@ -11474,6 +11497,7 @@ AttachPartitionForeignKey(List **wqueue,
 	if (!HeapTupleIsValid(parentConstrTup))
 		elog(ERROR, "cache lookup failed for constraint %u", parentConstrOid);
 	parentConstr = (Form_pg_constraint) GETSTRUCT(parentConstrTup);
+	parentConstrIsEnforced = parentConstr->conenforced;
 	parentConstrIsValid = parentConstr->convalidated;
 
 	/* Fetch the child constraint tuple */
@@ -11482,7 +11506,7 @@ AttachPartitionForeignKey(List **wqueue,
 	if (!HeapTupleIsValid(partcontup))
 		elog(ERROR, "cache lookup failed for constraint %u", partConstrOid);
 	partConstr = (Form_pg_constraint) GETSTRUCT(partcontup);
-	partConstrIsValid = parentConstr->convalidated;
+	partConstrIsValid = partConstr->convalidated;
 	partConstrFrelid = partConstr->confrelid;
 	partConstrRelid = partConstr->conrelid;
 
@@ -11503,17 +11527,21 @@ AttachPartitionForeignKey(List **wqueue,
 
 	/*
 	 * Like the constraint, attach partition's "check" triggers to the
-	 * corresponding parent triggers.
+	 * corresponding parent triggers if the constraint is enforced.
+	 * Non-enforced constraints do not have these triggers.
 	 */
-	GetForeignKeyCheckTriggers(trigrel,
-							   partConstrOid, partConstrFrelid, partConstrRelid,
-							   &insertTriggerOid, &updateTriggerOid);
-	Assert(OidIsValid(insertTriggerOid) && OidIsValid(parentInsTrigger));
-	TriggerSetParentTrigger(trigrel, insertTriggerOid, parentInsTrigger,
-							RelationGetRelid(partition));
-	Assert(OidIsValid(updateTriggerOid) && OidIsValid(parentUpdTrigger));
-	TriggerSetParentTrigger(trigrel, updateTriggerOid, parentUpdTrigger,
-							RelationGetRelid(partition));
+	if (parentConstrIsEnforced)
+	{
+		GetForeignKeyCheckTriggers(trigrel,
+								   partConstrOid, partConstrFrelid, partConstrRelid,
+								   &insertTriggerOid, &updateTriggerOid);
+		Assert(OidIsValid(insertTriggerOid) && OidIsValid(parentInsTrigger));
+		TriggerSetParentTrigger(trigrel, insertTriggerOid, parentInsTrigger,
+								RelationGetRelid(partition));
+		Assert(OidIsValid(updateTriggerOid) && OidIsValid(parentUpdTrigger));
+		TriggerSetParentTrigger(trigrel, updateTriggerOid, parentUpdTrigger,
+								RelationGetRelid(partition));
+	}
 
 	/*
 	 * If the referenced table is partitioned, then the partition we're
@@ -11641,6 +11669,10 @@ RemoveInheritedConstraint(Relation conrel, Relation trigrel, Oid conrelid,
  *
  * The subroutine for tryAttachPartitionForeignKey handles the deletion of
  * action triggers for the foreign key constraint.
+ *
+ * If valid confrelid and conrelid values are not provided, the respective
+ * trigger check will be skipped, and the trigger will be considered for
+ * removal.
  */
 static void
 DropForeignKeyConstraintTriggers(Relation trigrel, Oid conoid, Oid confrelid,
@@ -11661,10 +11693,27 @@ DropForeignKeyConstraintTriggers(Relation trigrel, Oid conoid, Oid confrelid,
 		Form_pg_trigger trgform = (Form_pg_trigger) GETSTRUCT(trigtup);
 		ObjectAddress trigger;
 
-		if (trgform->tgconstrrelid != conrelid)
+		/* Invalid if trigger is not for a referential integrity constraint */
+		if (!OidIsValid(trgform->tgconstrrelid))
 			continue;
-		if (trgform->tgrelid != confrelid)
+		if (OidIsValid(conrelid) && trgform->tgconstrrelid != conrelid)
 			continue;
+		if (OidIsValid(confrelid) && trgform->tgrelid != confrelid)
+			continue;
+
+		/* We should be droping trigger related to foreign ke constraint */
+		Assert(trgform->tgfoid == F_RI_FKEY_CHECK_INS ||
+			   trgform->tgfoid == F_RI_FKEY_CHECK_UPD ||
+			   trgform->tgfoid == F_RI_FKEY_CASCADE_DEL ||
+			   trgform->tgfoid == F_RI_FKEY_CASCADE_UPD ||
+			   trgform->tgfoid == F_RI_FKEY_RESTRICT_DEL ||
+			   trgform->tgfoid == F_RI_FKEY_RESTRICT_UPD ||
+			   trgform->tgfoid == F_RI_FKEY_SETNULL_DEL ||
+			   trgform->tgfoid == F_RI_FKEY_SETNULL_UPD ||
+			   trgform->tgfoid == F_RI_FKEY_SETDEFAULT_DEL ||
+			   trgform->tgfoid == F_RI_FKEY_SETDEFAULT_UPD ||
+			   trgform->tgfoid == F_RI_FKEY_NOACTION_DEL ||
+			   trgform->tgfoid == F_RI_FKEY_NOACTION_UPD);
 
 		/*
 		 * The constraint is originally set up to contain this trigger as an
@@ -11924,11 +11973,13 @@ ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd, bool recurse,
 	address = InvalidObjectAddress;
 	if (currcon->condeferrable != cmdcon->deferrable ||
 		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->conenforced != cmdcon->is_enforced ||
 		rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
 	{
 		if (ATExecAlterConstrRecurse(cmdcon, conrel, tgrel, currcon->conrelid,
 									 currcon->confrelid, contuple, &otherrelids,
-									 lockmode))
+									 lockmode, InvalidOid, InvalidOid, InvalidOid,
+									 InvalidOid))
 			ObjectAddressSet(address, ConstraintRelationId, currcon->oid);
 	}
 
@@ -11963,23 +12014,25 @@ static bool
 ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 						 const Oid fkrelid, const Oid pkrelid,
 						 HeapTuple contuple, List **otherrelids,
-						 LOCKMODE lockmode)
+						 LOCKMODE lockmode, Oid ReferencedParentDelTrigger,
+						 Oid ReferencedParentUpdTrigger,
+						 Oid ReferencingParentInsTrigger,
+						 Oid ReferencingParentUpdTrigger)
 {
 	Form_pg_constraint currcon;
 	Oid			conoid;
+	Oid			conrelid;
 	Oid			refrelid;
 	bool		changed = false;
-	Relation	rel;
 
 	/* since this function recurses, it could be driven to stack overflow */
 	check_stack_depth();
 
 	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
 	conoid = currcon->oid;
+	conrelid = currcon->conrelid;
 	refrelid = currcon->confrelid;
 
-	rel = table_open(currcon->conrelid, lockmode);
-
 	/*
 	 * Update pg_constraint with the flags from cmdcon.
 	 *
@@ -11987,7 +12040,8 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 	 * silently do nothing.
 	 */
 	if (currcon->condeferrable != cmdcon->deferrable ||
-		currcon->condeferred != cmdcon->initdeferred)
+		currcon->condeferred != cmdcon->initdeferred ||
+		currcon->conenforced != cmdcon->is_enforced)
 	{
 		HeapTuple	copyTuple;
 		Form_pg_constraint copy_con;
@@ -11996,6 +12050,18 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
 		copy_con->condeferrable = cmdcon->deferrable;
 		copy_con->condeferred = cmdcon->initdeferred;
+		copy_con->conenforced = cmdcon->is_enforced;
+
+		/*
+		 * NB: The convalidated status is irrelevant when the constraint is
+		 * set to NOT ENFORCED, but for consistency, it should be set
+		 * accordingly. This ensures that if the constraint is later changed
+		 * to ENFORCED, it will automatically be in the correct NOT VALID
+		 * state.
+		 */
+		if (!cmdcon->is_enforced)
+			copy_con->convalidated = false;
+
 		CatalogTupleUpdate(conrel, &copyTuple->t_self, copyTuple);
 
 		InvokeObjectPostAlterHook(ConstraintRelationId,
@@ -12005,33 +12071,161 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 		changed = true;
 
 		/* Make new constraint flags visible to others */
-		CacheInvalidateRelcache(rel);
+		CacheInvalidateRelcacheByRelid(conrelid);
+	}
 
+	if (currcon->conenforced != cmdcon->is_enforced)
+	{
+		ATExecAlterConstrEnforceability(cmdcon, conrel, tgrel, fkrelid, pkrelid,
+										contuple, otherrelids, lockmode,
+										ReferencedParentDelTrigger,
+										ReferencedParentUpdTrigger,
+										ReferencingParentInsTrigger,
+										ReferencingParentUpdTrigger);
+	}
+	else
+	{
 		/*
 		 * Now we need to update the multiple entries in pg_trigger that
 		 * implement the constraint.
 		 */
-		AlterConstrTriggerDeferrability(conoid, tgrel, rel, cmdcon->deferrable,
-										cmdcon->initdeferred, otherrelids);
-	}
+		AlterConstrTriggerDeferrability(conoid, tgrel, conrelid,
+										cmdcon->deferrable,
+										cmdcon->initdeferred,
+										otherrelids);
 
-	/*
-	 * If the table at either end of the constraint is partitioned, we need to
-	 * recurse and handle every constraint that is a child of this one.
-	 *
-	 * (This assumes that the recurse flag is forcibly set for partitioned
-	 * tables, and not set for legacy inheritance, though we don't check for
-	 * that here.)
-	 */
-	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
-		get_rel_relkind(refrelid) == RELKIND_PARTITIONED_TABLE)
-		ATExecAlterChildConstr(cmdcon, conrel, tgrel, fkrelid, pkrelid,
-							   contuple, otherrelids, lockmode);
-	table_close(rel, NoLock);
+		/*
+		 * If the table at either end of the constraint is partitioned, we
+		 * need to recurse and handle every constraint that is a child of this
+		 * one.
+		 *
+		 * (This assumes that the recurse flag is forcibly set for partitioned
+		 * tables, and not set for legacy inheritance, though we don't check
+		 * for that here.)
+		 */
+		if (get_rel_relkind(conrelid) == RELKIND_PARTITIONED_TABLE ||
+			get_rel_relkind(refrelid) == RELKIND_PARTITIONED_TABLE)
+			ATExecAlterChildConstr(cmdcon, conrel, tgrel, fkrelid, pkrelid,
+								   contuple, otherrelids, lockmode);
+	}
 
 	return changed;
 }
 
+/*
+ * A subroutine of ATExecAlterConstrRecurse that updates the enforceability of
+ * a foreign key constraint. Depending on whether the constraint is being set
+ * to enforced or not enforced, it creates or drops the trigger accordingly.
+ *
+ * The arguments to this function have the same meaning as the arguments to
+ * ATExecAlterConstrRecurse.
+ */
+static void
+ATExecAlterConstrEnforceability(Constraint *cmdcon, Relation conrel,
+								Relation tgrel, const Oid fkrelid,
+								const Oid pkrelid, HeapTuple contuple,
+								List **otherrelids, LOCKMODE lockmode,
+								Oid ReferencedParentDelTrigger,
+								Oid ReferencedParentUpdTrigger,
+								Oid ReferencingParentInsTrigger,
+								Oid ReferencingParentUpdTrigger)
+{
+	Form_pg_constraint currcon;
+	Oid			conoid;
+
+	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
+	conoid = currcon->oid;
+
+	/* Drop triggers */
+	if (!cmdcon->is_enforced)
+	{
+		/*
+		 * When setting a constraint to NOT ENFORCED, the constraint triggers
+		 * need to be dropped. Therefore, we must process the child relations
+		 * first, followed by the parent, to account for dependencies.
+		 */
+		if (get_rel_relkind(currcon->conrelid) == RELKIND_PARTITIONED_TABLE ||
+			get_rel_relkind(currcon->confrelid) == RELKIND_PARTITIONED_TABLE)
+			ATExecAlterChildConstr(cmdcon, conrel, tgrel, fkrelid, pkrelid,
+								   contuple, otherrelids, lockmode);
+
+		/* Drop all the triggers */
+		DropForeignKeyConstraintTriggers(tgrel, conoid, InvalidOid, InvalidOid);
+	}
+	else						/* Create triggers */
+	{
+		Relation	rel;
+		Oid			ReferencedDelTriggerOid = InvalidOid,
+					ReferencedUpdTriggerOid = InvalidOid,
+					ReferencingInsTriggerOid = InvalidOid,
+					ReferencingUpdTriggerOid = InvalidOid;
+
+		/* Update the foreign key action required for trigger creation. */
+		cmdcon->fk_matchtype = currcon->confmatchtype;
+		cmdcon->fk_upd_action = currcon->confupdtype;
+		cmdcon->fk_del_action = currcon->confdeltype;
+
+		rel = table_open(currcon->conrelid, lockmode);
+
+		/* Create referenced triggers */
+		if (currcon->conrelid == fkrelid)
+			createForeignKeyActionTriggers(rel,
+										   currcon->confrelid,
+										   cmdcon,
+										   conoid,
+										   currcon->conindid,
+										   ReferencedParentDelTrigger,
+										   ReferencedParentUpdTrigger,
+										   &ReferencedDelTriggerOid,
+										   &ReferencedUpdTriggerOid);
+
+		/* Create referencing triggers */
+		if (currcon->confrelid == pkrelid)
+			createForeignKeyCheckTriggers(currcon->conrelid,
+										  pkrelid,
+										  cmdcon,
+										  conoid,
+										  currcon->conindid,
+										  ReferencingParentInsTrigger,
+										  ReferencingParentUpdTrigger,
+										  &ReferencingInsTriggerOid,
+										  &ReferencingUpdTriggerOid);
+
+		/*
+		 * If the table at either end of the constraint is partitioned, we
+		 * need to recurse and create triggers for each constraint that is a
+		 * child of this one.
+		 */
+		if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
+			get_rel_relkind(currcon->confrelid) == RELKIND_PARTITIONED_TABLE)
+		{
+			ScanKeyData pkey;
+			SysScanDesc pscan;
+			HeapTuple	childtup;
+
+			ScanKeyInit(&pkey,
+						Anum_pg_constraint_conparentid,
+						BTEqualStrategyNumber, F_OIDEQ,
+						ObjectIdGetDatum(conoid));
+
+			pscan = systable_beginscan(conrel, ConstraintParentIndexId,
+									   true, NULL, 1, &pkey);
+
+			while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
+				ATExecAlterConstrRecurse(cmdcon, conrel, tgrel, fkrelid, pkrelid,
+										 childtup, otherrelids, lockmode,
+										 ReferencedDelTriggerOid,
+										 ReferencedUpdTriggerOid,
+										 ReferencingInsTriggerOid,
+										 ReferencingUpdTriggerOid);
+
+			systable_endscan(pscan);
+		}
+
+		table_close(rel, NoLock);
+	}
+}
+
 /*
  * A subroutine of ATExecAlterConstrRecurse that updated constraint trigger's
  * deferrability.
@@ -12040,7 +12234,7 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
  * ATExecAlterConstrRecurse.
  */
 static void
-AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
+AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Oid fkrel,
 								bool deferrable, bool initdeferred,
 								List **otherrelids)
 {
@@ -12066,7 +12260,7 @@ AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
 		 * other rels that don't have a trigger whose properties change, but
 		 * let's be conservative.)
 		 */
-		if (tgform->tgrelid != RelationGetRelid(rel))
+		if (tgform->tgrelid != fkrel)
 			*otherrelids = list_append_unique_oid(*otherrelids,
 												  tgform->tgrelid);
 
@@ -12129,7 +12323,8 @@ ATExecAlterChildConstr(Constraint *cmdcon, Relation conrel, Relation tgrel,
 
 	while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
 		ATExecAlterConstrRecurse(cmdcon, conrel, tgrel, fkrelid, pkrelid,
-								 childtup, otherrelids, lockmode);
+								 childtup, otherrelids, lockmode, InvalidOid,
+								 InvalidOid, InvalidOid, InvalidOid);
 
 	systable_endscan(pscan);
 }
@@ -20154,8 +20349,6 @@ DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
 		ForeignKeyCacheInfo *fk = lfirst(cell);
 		HeapTuple	contup;
 		Form_pg_constraint conform;
-		Oid			insertTriggerOid,
-					updateTriggerOid;
 
 		contup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
 		if (!HeapTupleIsValid(contup))
@@ -20178,17 +20371,25 @@ DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
 
 		/*
 		 * Also, look up the partition's "check" triggers corresponding to the
-		 * constraint being detached and detach them from the parent triggers.
+		 * enforced constraint being detached and detach them from the parent
+		 * triggers. Non-enforced constraints do not have these triggers;
+		 * therefore, this step is not needed.
 		 */
-		GetForeignKeyCheckTriggers(trigrel,
-								   fk->conoid, fk->confrelid, fk->conrelid,
-								   &insertTriggerOid, &updateTriggerOid);
-		Assert(OidIsValid(insertTriggerOid));
-		TriggerSetParentTrigger(trigrel, insertTriggerOid, InvalidOid,
-								RelationGetRelid(partRel));
-		Assert(OidIsValid(updateTriggerOid));
-		TriggerSetParentTrigger(trigrel, updateTriggerOid, InvalidOid,
-								RelationGetRelid(partRel));
+		if (fk->conenforced)
+		{
+			Oid			insertTriggerOid,
+						updateTriggerOid;
+
+			GetForeignKeyCheckTriggers(trigrel,
+									   fk->conoid, fk->confrelid, fk->conrelid,
+									   &insertTriggerOid, &updateTriggerOid);
+			Assert(OidIsValid(insertTriggerOid));
+			TriggerSetParentTrigger(trigrel, insertTriggerOid, InvalidOid,
+									RelationGetRelid(partRel));
+			Assert(OidIsValid(updateTriggerOid));
+			TriggerSetParentTrigger(trigrel, updateTriggerOid, InvalidOid,
+									RelationGetRelid(partRel));
+		}
 
 		/*
 		 * Lastly, create the action triggers on the referenced table, using
@@ -20228,8 +20429,9 @@ DetachPartitionFinalize(Relation rel, Relation partRel, bool concurrent,
 			fkconstraint->conname = pstrdup(NameStr(conform->conname));
 			fkconstraint->deferrable = conform->condeferrable;
 			fkconstraint->initdeferred = conform->condeferred;
+			fkconstraint->is_enforced = conform->conenforced;
 			fkconstraint->skip_validation = true;
-			fkconstraint->initially_valid = true;
+			fkconstraint->initially_valid = conform->convalidated;
 			/* a few irrelevant fields omitted here */
 			fkconstraint->pktable = NULL;
 			fkconstraint->fk_attrs = NIL;
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index d7f9c00c409..37082bc511e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -2666,7 +2666,7 @@ alter_table_cmd:
 					processCASbits($4, @4, "ALTER CONSTRAINT statement",
 									&c->deferrable,
 									&c->initdeferred,
-									NULL, NULL, NULL, yyscanner);
+									&c->is_enforced, NULL, NULL, yyscanner);
 					$$ = (Node *) n;
 				}
 			/* ALTER TABLE <name> VALIDATE CONSTRAINT ... */
@@ -4035,6 +4035,7 @@ ColConstraintElem:
 					n->is_enforced = true;
 					n->skip_validation = false;
 					n->initially_valid = true;
+					n->is_enforced = true;
 					$$ = (Node *) n;
 				}
 		;
@@ -4309,8 +4310,8 @@ ConstraintElem:
 					n->fk_del_set_cols = ($11)->deleteAction->cols;
 					processCASbits($12, @12, "FOREIGN KEY",
 								   &n->deferrable, &n->initdeferred,
-								   NULL, &n->skip_validation, NULL,
-								   yyscanner);
+								   &n->is_enforced, &n->skip_validation,
+								   NULL, yyscanner);
 					n->initially_valid = !n->skip_validation;
 					$$ = (Node *) n;
 				}
diff --git a/src/backend/parser/parse_utilcmd.c b/src/backend/parser/parse_utilcmd.c
index ca028d2a66d..170f8032d59 100644
--- a/src/backend/parser/parse_utilcmd.c
+++ b/src/backend/parser/parse_utilcmd.c
@@ -2961,8 +2961,10 @@ transformFKConstraints(CreateStmtContext *cxt,
 
 	/*
 	 * If CREATE TABLE or adding a column with NULL default, we can safely
-	 * skip validation of FK constraints, and nonetheless mark them valid.
-	 * (This will override any user-supplied NOT VALID flag.)
+	 * skip validation of FK constraints, and mark them as valid based on the
+	 * constraint enforcement flag, since NOT ENFORCED constraints must always
+	 * be marked as NOT VALID. (This will override any user-supplied NOT VALID
+	 * flag.)
 	 */
 	if (skipValidation)
 	{
@@ -2971,7 +2973,7 @@ transformFKConstraints(CreateStmtContext *cxt,
 			Constraint *constraint = (Constraint *) lfirst(fkclist);
 
 			constraint->skip_validation = true;
-			constraint->initially_valid = true;
+			constraint->initially_valid = constraint->is_enforced;
 		}
 	}
 
@@ -3966,7 +3968,8 @@ transformConstraintAttrs(CreateStmtContext *cxt, List *constraintList)
 
 			case CONSTR_ATTR_ENFORCED:
 				if (lastprimarycon == NULL ||
-					lastprimarycon->contype != CONSTR_CHECK)
+					(lastprimarycon->contype != CONSTR_CHECK &&
+					 lastprimarycon->contype != CONSTR_FOREIGN))
 					ereport(ERROR,
 							(errcode(ERRCODE_SYNTAX_ERROR),
 							 errmsg("misplaced ENFORCED clause"),
@@ -3982,7 +3985,8 @@ transformConstraintAttrs(CreateStmtContext *cxt, List *constraintList)
 
 			case CONSTR_ATTR_NOT_ENFORCED:
 				if (lastprimarycon == NULL ||
-					lastprimarycon->contype != CONSTR_CHECK)
+					(lastprimarycon->contype != CONSTR_CHECK &&
+					 lastprimarycon->contype != CONSTR_FOREIGN))
 					ereport(ERROR,
 							(errcode(ERRCODE_SYNTAX_ERROR),
 							 errmsg("misplaced NOT ENFORCED clause"),
diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c
index 485cd2178bc..cb3c19c7448 100644
--- a/src/backend/utils/cache/relcache.c
+++ b/src/backend/utils/cache/relcache.c
@@ -4689,6 +4689,7 @@ RelationGetFKeyList(Relation relation)
 		info->conoid = constraint->oid;
 		info->conrelid = constraint->conrelid;
 		info->confrelid = constraint->confrelid;
+		info->conenforced = constraint->conenforced;
 
 		DeconstructFkConstraintRow(htup, &info->nkeys,
 								   info->conkey,
diff --git a/src/include/utils/rel.h b/src/include/utils/rel.h
index 33d1e4a4e2e..c707ebec7b6 100644
--- a/src/include/utils/rel.h
+++ b/src/include/utils/rel.h
@@ -284,6 +284,9 @@ typedef struct ForeignKeyCacheInfo
 	/* number of columns in the foreign key */
 	int			nkeys;
 
+	/* Is enforced ? */
+	bool		conenforced;
+
 	/*
 	 * these arrays each have nkeys valid entries:
 	 */
diff --git a/src/test/regress/expected/constraints.out b/src/test/regress/expected/constraints.out
index 692a69fe457..f8767c5cacf 100644
--- a/src/test/regress/expected/constraints.out
+++ b/src/test/regress/expected/constraints.out
@@ -746,13 +746,9 @@ LINE 1: CREATE TABLE UNIQUE_NOTEN_TBL(i int UNIQUE NOT ENFORCED);
                                                    ^
 -- XXX: error message is misleading here
 ALTER TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key ENFORCED;
-ERROR:  ALTER CONSTRAINT statement constraints cannot be marked ENFORCED
-LINE 1: ...TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key ENFORCED;
-                                                              ^
+ERROR:  constraint "unique_tbl_i_key" of relation "unique_tbl" is not a foreign key constraint
 ALTER TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key NOT ENFORCED;
-ERROR:  ALTER CONSTRAINT statement constraints cannot be marked NOT ENFORCED
-LINE 1: ...ABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key NOT ENFORC...
-                                                             ^
+ERROR:  constraint "unique_tbl_i_key" of relation "unique_tbl" is not a foreign key constraint
 DROP TABLE unique_tbl;
 --
 -- EXCLUDE constraints
diff --git a/src/test/regress/expected/foreign_key.out b/src/test/regress/expected/foreign_key.out
index f617d519aef..9f6f22dd988 100644
--- a/src/test/regress/expected/foreign_key.out
+++ b/src/test/regress/expected/foreign_key.out
@@ -1,12 +1,44 @@
 --
 -- FOREIGN KEY
 --
--- MATCH FULL
+-- NOT ENFORCED
 --
 -- First test, check and cascade
 --
 CREATE TABLE PKTABLE ( ptest1 int PRIMARY KEY, ptest2 text );
-CREATE TABLE FKTABLE ( ftest1 int REFERENCES PKTABLE MATCH FULL ON DELETE CASCADE ON UPDATE CASCADE, ftest2 int );
+CREATE TABLE FKTABLE ( ftest1 int REFERENCES PKTABLE MATCH FULL ON DELETE CASCADE ON UPDATE CASCADE NOT ENFORCED,
+					   ftest2 int );
+-- Inserting into the foreign key table will not result in an error, even if
+-- there is no matching key in the referenced table.
+INSERT INTO FKTABLE VALUES (1, 2);
+INSERT INTO FKTABLE VALUES (2, 3);
+-- Check FKTABLE
+SELECT * FROM FKTABLE;
+ ftest1 | ftest2 
+--------+--------
+      1 |      2
+      2 |      3
+(2 rows)
+
+-- Changing it back to ENFORCED will leave the constraint in the NOT VALID state
+ALTER TABLE FKTABLE ALTER CONSTRAINT fktable_ftest1_fkey ENFORCED;
+-- Which needs to be explicitly validated.
+ALTER TABLE FKTABLE VALIDATE CONSTRAINT fktable_ftest1_fkey;
+ERROR:  insert or update on table "fktable" violates foreign key constraint "fktable_ftest1_fkey"
+DETAIL:  Key (ftest1)=(1) is not present in table "pktable".
+-- Remove any existing rows that violate the constraint, then attempt to change
+-- it.
+TRUNCATE FKTABLE;
+ALTER TABLE FKTABLE VALIDATE CONSTRAINT fktable_ftest1_fkey;
+-- Any further inserts will fail due to the enforcement.
+INSERT INTO FKTABLE VALUES (3, 4);
+ERROR:  insert or update on table "fktable" violates foreign key constraint "fktable_ftest1_fkey"
+DETAIL:  Key (ftest1)=(3) is not present in table "pktable".
+--
+-- MATCH FULL
+--
+-- First test, check and cascade
+--
 -- Insert test data into PKTABLE
 INSERT INTO PKTABLE VALUES (1, 'Test1');
 INSERT INTO PKTABLE VALUES (2, 'Test2');
@@ -351,6 +383,8 @@ INSERT INTO FKTABLE VALUES (1, NULL);
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2) REFERENCES PKTABLE MATCH FULL;
 ERROR:  insert or update on table "fktable" violates foreign key constraint "fktable_ftest1_ftest2_fkey"
 DETAIL:  MATCH FULL does not allow mixing of null and nonnull key values.
+-- NOT ENFORCED will bypass the initial check.
+ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2) REFERENCES PKTABLE MATCH FULL NOT ENFORCED;
 DROP TABLE FKTABLE;
 DROP TABLE PKTABLE;
 -- MATCH SIMPLE
@@ -1276,13 +1310,28 @@ INSERT INTO fktable VALUES (0, 20);
 ERROR:  insert or update on table "fktable" violates foreign key constraint "fktable_fk_fkey"
 DETAIL:  Key (fk)=(20) is not present in table "pktable".
 COMMIT;
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT ENFORCED;
+BEGIN;
+-- doesn't match FK, no error.
+UPDATE pktable SET id = 10 WHERE id = 5;
+-- doesn't match PK, no error.
+INSERT INTO fktable VALUES (0, 20);
+ROLLBACK;
 -- try additional syntax
-ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE;
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE ENFORCED;
 -- illegal option
 ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY DEFERRED;
 ERROR:  constraint declared INITIALLY DEFERRED must be DEFERRABLE
 LINE 1: ...e ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY ...
                                                              ^
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey ENFORCED NOT ENFORCED;
+ERROR:  conflicting constraint properties
+LINE 1: ...fktable ALTER CONSTRAINT fktable_fk_fkey ENFORCED NOT ENFORC...
+                                                             ^
+CREATE TEMP TABLE fktable2 (fk int references pktable ENFORCED NOT ENFORCED);
+ERROR:  multiple ENFORCED/NOT ENFORCED clauses not allowed
+LINE 1: ...ABLE fktable2 (fk int references pktable ENFORCED NOT ENFORC...
+                                                             ^
 -- test order of firing of FK triggers when several RI-induced changes need to
 -- be made to the same row.  This was broken by subtransaction-related
 -- changes in 8.0.
@@ -1650,10 +1699,14 @@ ALTER TABLE fk_partitioned_fk DROP COLUMN fdrop1;
 CREATE TABLE fk_partitioned_fk_1 (fdrop1 int, fdrop2 int, a int, fdrop3 int, b int);
 ALTER TABLE fk_partitioned_fk_1 DROP COLUMN fdrop1, DROP COLUMN fdrop2, DROP COLUMN fdrop3;
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_1 FOR VALUES FROM (0,0) TO (1000,1000);
-ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk;
+ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT ENFORCED;
 CREATE TABLE fk_partitioned_fk_2 (b int, fdrop1 int, fdrop2 int, a int);
 ALTER TABLE fk_partitioned_fk_2 DROP COLUMN fdrop1, DROP COLUMN fdrop2;
+ALTER TABLE fk_partitioned_fk_2 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT ENFORCED;
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES FROM (1000,1000) TO (2000,2000);
+-- Changing to ENFORCED does not alter the validation status; it must be explicitly validated.
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey ENFORCED;
+ALTER TABLE fk_partitioned_fk VALIDATE CONSTRAINT fk_partitioned_fk_a_b_fkey ;
 CREATE TABLE fk_partitioned_fk_3 (fdrop1 int, fdrop2 int, fdrop3 int, fdrop4 int, b int, a int)
   PARTITION BY HASH (a);
 ALTER TABLE fk_partitioned_fk_3 DROP COLUMN fdrop1, DROP COLUMN fdrop2,
@@ -1676,10 +1729,10 @@ INSERT INTO fk_partitioned_fk_1 (a,b) VALUES (500, 501);
 ERROR:  insert or update on table "fk_partitioned_fk_1" violates foreign key constraint "fk_partitioned_fk_a_b_fkey"
 DETAIL:  Key (a, b)=(500, 501) is not present in table "fk_notpartitioned_pk".
 INSERT INTO fk_partitioned_fk (a,b) VALUES (1500, 1501);
-ERROR:  insert or update on table "fk_partitioned_fk_2" violates foreign key constraint "fk_partitioned_fk_a_b_fkey"
+ERROR:  insert or update on table "fk_partitioned_fk_2" violates foreign key constraint "fk_partitioned_fk_2_a_b_fkey"
 DETAIL:  Key (a, b)=(1500, 1501) is not present in table "fk_notpartitioned_pk".
 INSERT INTO fk_partitioned_fk_2 (a,b) VALUES (1500, 1501);
-ERROR:  insert or update on table "fk_partitioned_fk_2" violates foreign key constraint "fk_partitioned_fk_a_b_fkey"
+ERROR:  insert or update on table "fk_partitioned_fk_2" violates foreign key constraint "fk_partitioned_fk_2_a_b_fkey"
 DETAIL:  Key (a, b)=(1500, 1501) is not present in table "fk_notpartitioned_pk".
 INSERT INTO fk_partitioned_fk (a,b) VALUES (2500, 2502);
 ERROR:  insert or update on table "fk_partitioned_fk_3_1" violates foreign key constraint "fk_partitioned_fk_a_b_fkey"
@@ -1729,6 +1782,37 @@ Indexes:
 Referenced by:
     TABLE "fk_partitioned_fk" CONSTRAINT "fk_partitioned_fk_a_b_fkey" FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b)
 
+-- Check the exsting FK trigger
+CREATE TEMP TABLE tmp_trg_info AS SELECT tgtype, tgrelid::regclass, tgconstraint
+FROM pg_trigger
+WHERE tgrelid IN (SELECT relid FROM pg_partition_tree('fk_partitioned_fk'::regclass)
+					UNION ALL SELECT 'fk_notpartitioned_pk'::regclass);
+SELECT count(1) FROM tmp_trg_info;
+ count 
+-------
+    14
+(1 row)
+
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey NOT ENFORCED;
+-- No triggers
+SELECT count(1) FROM pg_trigger
+WHERE tgrelid IN (SELECT relid FROM pg_partition_tree('fk_partitioned_fk'::regclass)
+					UNION ALL SELECT 'fk_notpartitioned_pk'::regclass);
+ count 
+-------
+     0
+(1 row)
+
+-- Changing it back to ENFORCED will recreate the necessary triggers.
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey ENFORCED;
+-- Should be exactly the same number of triggers found as before
+SELECT COUNT(1) FROM pg_trigger pgt JOIN tmp_trg_info tt
+ON (pgt.tgtype = tt.tgtype AND pgt.tgrelid = tt.tgrelid AND pgt.tgconstraint = tt.tgconstraint);
+ count 
+-------
+    14
+(1 row)
+
 ALTER TABLE fk_partitioned_fk DROP CONSTRAINT fk_partitioned_fk_a_b_fkey;
 -- done.
 DROP TABLE fk_notpartitioned_pk, fk_partitioned_fk;
@@ -1932,6 +2016,40 @@ Partition of: fk_partitioned_fk FOR VALUES IN (1500, 1502)
 Foreign-key constraints:
     TABLE "fk_partitioned_fk" CONSTRAINT "fk_partitioned_fk_a_b_fkey" FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE
 
+DROP TABLE fk_partitioned_fk_2;
+CREATE TABLE fk_partitioned_fk_2 (b int, a int,
+	FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk ON UPDATE CASCADE ON DELETE CASCADE NOT ENFORCED);
+BEGIN;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES IN (1500,1502);
+-- should have two constraints
+\d fk_partitioned_fk_2
+        Table "public.fk_partitioned_fk_2"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ b      | integer |           |          | 
+ a      | integer |           |          | 
+Partition of: fk_partitioned_fk FOR VALUES IN (1500, 1502)
+Foreign-key constraints:
+    "fk_partitioned_fk_2_a_b_fkey" FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE NOT ENFORCED
+    TABLE "fk_partitioned_fk" CONSTRAINT "fk_partitioned_fk_a_b_fkey" FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE
+
+DROP TABLE fk_partitioned_fk_2;
+ROLLBACK;
+BEGIN;
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey NOT ENFORCED;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES IN (1500,1502);
+-- should have only one constraint
+\d fk_partitioned_fk_2
+        Table "public.fk_partitioned_fk_2"
+ Column |  Type   | Collation | Nullable | Default 
+--------+---------+-----------+----------+---------
+ b      | integer |           |          | 
+ a      | integer |           |          | 
+Partition of: fk_partitioned_fk FOR VALUES IN (1500, 1502)
+Foreign-key constraints:
+    TABLE "fk_partitioned_fk" CONSTRAINT "fk_partitioned_fk_a_b_fkey" FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE NOT ENFORCED
+
+ROLLBACK;
 DROP TABLE fk_partitioned_fk_2;
 CREATE TABLE fk_partitioned_fk_4 (a int, b int, FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE) PARTITION BY RANGE (b, a);
 CREATE TABLE fk_partitioned_fk_4_1 PARTITION OF fk_partitioned_fk_4 FOR VALUES FROM (1,1) TO (100,100);
diff --git a/src/test/regress/sql/foreign_key.sql b/src/test/regress/sql/foreign_key.sql
index d5f68812ba6..98f47873d41 100644
--- a/src/test/regress/sql/foreign_key.sql
+++ b/src/test/regress/sql/foreign_key.sql
@@ -2,13 +2,40 @@
 -- FOREIGN KEY
 --
 
--- MATCH FULL
+-- NOT ENFORCED
 --
 -- First test, check and cascade
 --
 CREATE TABLE PKTABLE ( ptest1 int PRIMARY KEY, ptest2 text );
-CREATE TABLE FKTABLE ( ftest1 int REFERENCES PKTABLE MATCH FULL ON DELETE CASCADE ON UPDATE CASCADE, ftest2 int );
+CREATE TABLE FKTABLE ( ftest1 int REFERENCES PKTABLE MATCH FULL ON DELETE CASCADE ON UPDATE CASCADE NOT ENFORCED,
+					   ftest2 int );
 
+-- Inserting into the foreign key table will not result in an error, even if
+-- there is no matching key in the referenced table.
+INSERT INTO FKTABLE VALUES (1, 2);
+INSERT INTO FKTABLE VALUES (2, 3);
+
+-- Check FKTABLE
+SELECT * FROM FKTABLE;
+
+-- Changing it back to ENFORCED will leave the constraint in the NOT VALID state
+ALTER TABLE FKTABLE ALTER CONSTRAINT fktable_ftest1_fkey ENFORCED;
+-- Which needs to be explicitly validated.
+ALTER TABLE FKTABLE VALIDATE CONSTRAINT fktable_ftest1_fkey;
+
+-- Remove any existing rows that violate the constraint, then attempt to change
+-- it.
+TRUNCATE FKTABLE;
+ALTER TABLE FKTABLE VALIDATE CONSTRAINT fktable_ftest1_fkey;
+
+-- Any further inserts will fail due to the enforcement.
+INSERT INTO FKTABLE VALUES (3, 4);
+
+--
+-- MATCH FULL
+--
+-- First test, check and cascade
+--
 -- Insert test data into PKTABLE
 INSERT INTO PKTABLE VALUES (1, 'Test1');
 INSERT INTO PKTABLE VALUES (2, 'Test2');
@@ -230,6 +257,9 @@ INSERT INTO FKTABLE VALUES (1, NULL);
 
 ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2) REFERENCES PKTABLE MATCH FULL;
 
+-- NOT ENFORCED will bypass the initial check.
+ALTER TABLE FKTABLE ADD FOREIGN KEY(ftest1, ftest2) REFERENCES PKTABLE MATCH FULL NOT ENFORCED;
+
 DROP TABLE FKTABLE;
 DROP TABLE PKTABLE;
 
@@ -968,10 +998,23 @@ INSERT INTO fktable VALUES (0, 20);
 
 COMMIT;
 
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT ENFORCED;
+
+BEGIN;
+
+-- doesn't match FK, no error.
+UPDATE pktable SET id = 10 WHERE id = 5;
+-- doesn't match PK, no error.
+INSERT INTO fktable VALUES (0, 20);
+
+ROLLBACK;
+
 -- try additional syntax
-ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE;
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE ENFORCED;
 -- illegal option
 ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey NOT DEFERRABLE INITIALLY DEFERRED;
+ALTER TABLE fktable ALTER CONSTRAINT fktable_fk_fkey ENFORCED NOT ENFORCED;
+CREATE TEMP TABLE fktable2 (fk int references pktable ENFORCED NOT ENFORCED);
 
 -- test order of firing of FK triggers when several RI-induced changes need to
 -- be made to the same row.  This was broken by subtransaction-related
@@ -1236,11 +1279,16 @@ ALTER TABLE fk_partitioned_fk DROP COLUMN fdrop1;
 CREATE TABLE fk_partitioned_fk_1 (fdrop1 int, fdrop2 int, a int, fdrop3 int, b int);
 ALTER TABLE fk_partitioned_fk_1 DROP COLUMN fdrop1, DROP COLUMN fdrop2, DROP COLUMN fdrop3;
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_1 FOR VALUES FROM (0,0) TO (1000,1000);
-ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk;
+ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT ENFORCED;
 CREATE TABLE fk_partitioned_fk_2 (b int, fdrop1 int, fdrop2 int, a int);
 ALTER TABLE fk_partitioned_fk_2 DROP COLUMN fdrop1, DROP COLUMN fdrop2;
+ALTER TABLE fk_partitioned_fk_2 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT ENFORCED;
 ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES FROM (1000,1000) TO (2000,2000);
 
+-- Changing to ENFORCED does not alter the validation status; it must be explicitly validated.
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey ENFORCED;
+ALTER TABLE fk_partitioned_fk VALIDATE CONSTRAINT fk_partitioned_fk_a_b_fkey ;
+
 CREATE TABLE fk_partitioned_fk_3 (fdrop1 int, fdrop2 int, fdrop3 int, fdrop4 int, b int, a int)
   PARTITION BY HASH (a);
 ALTER TABLE fk_partitioned_fk_3 DROP COLUMN fdrop1, DROP COLUMN fdrop2,
@@ -1286,6 +1334,27 @@ UPDATE fk_notpartitioned_pk SET b = 1502 WHERE a = 1500;
 UPDATE fk_notpartitioned_pk SET b = 2504 WHERE a = 2500;
 -- check psql behavior
 \d fk_notpartitioned_pk
+
+-- Check the exsting FK trigger
+CREATE TEMP TABLE tmp_trg_info AS SELECT tgtype, tgrelid::regclass, tgconstraint
+FROM pg_trigger
+WHERE tgrelid IN (SELECT relid FROM pg_partition_tree('fk_partitioned_fk'::regclass)
+					UNION ALL SELECT 'fk_notpartitioned_pk'::regclass);
+SELECT count(1) FROM tmp_trg_info;
+
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey NOT ENFORCED;
+-- No triggers
+SELECT count(1) FROM pg_trigger
+WHERE tgrelid IN (SELECT relid FROM pg_partition_tree('fk_partitioned_fk'::regclass)
+					UNION ALL SELECT 'fk_notpartitioned_pk'::regclass);
+
+-- Changing it back to ENFORCED will recreate the necessary triggers.
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey ENFORCED;
+
+-- Should be exactly the same number of triggers found as before
+SELECT COUNT(1) FROM pg_trigger pgt JOIN tmp_trg_info tt
+ON (pgt.tgtype = tt.tgtype AND pgt.tgrelid = tt.tgrelid AND pgt.tgconstraint = tt.tgconstraint);
+
 ALTER TABLE fk_partitioned_fk DROP CONSTRAINT fk_partitioned_fk_a_b_fkey;
 -- done.
 DROP TABLE fk_notpartitioned_pk, fk_partitioned_fk;
@@ -1422,6 +1491,22 @@ ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES IN
 \d fk_partitioned_fk_2
 DROP TABLE fk_partitioned_fk_2;
 
+CREATE TABLE fk_partitioned_fk_2 (b int, a int,
+	FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk ON UPDATE CASCADE ON DELETE CASCADE NOT ENFORCED);
+BEGIN;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES IN (1500,1502);
+-- should have two constraints
+\d fk_partitioned_fk_2
+DROP TABLE fk_partitioned_fk_2;
+ROLLBACK;
+BEGIN;
+ALTER TABLE fk_partitioned_fk ALTER CONSTRAINT fk_partitioned_fk_a_b_fkey NOT ENFORCED;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES IN (1500,1502);
+-- should have only one constraint
+\d fk_partitioned_fk_2
+ROLLBACK;
+DROP TABLE fk_partitioned_fk_2;
+
 CREATE TABLE fk_partitioned_fk_4 (a int, b int, FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE CASCADE ON DELETE CASCADE) PARTITION BY RANGE (b, a);
 CREATE TABLE fk_partitioned_fk_4_1 PARTITION OF fk_partitioned_fk_4 FOR VALUES FROM (1,1) TO (100,100);
 CREATE TABLE fk_partitioned_fk_4_2 (a int, b int, FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk(a, b) ON UPDATE SET NULL);
-- 
2.43.5