Allow NOT VALID foreign key constraints on partitioned tables

This feature was intentionally omitted when FKs were first implemented
for partitioned tables, and had been requested a few times; the
usefulness is clear.

Validation can happen for each partition individually, which is useful
to contain the number of locks held and the duration; or it can be
executed for the partitioning hierarchy as a single command, which
validates all child constraints that haven't been validated already.

This is also useful to implement NOT ENFORCED constraints on top.

Author: Amul Sul <[email protected]>
Discussion: https://postgr.es/m/CAAJ_b96Bp=-ZwihPPtuaNX=SrZ0U6ZsXD3+fgARO0JuKa8v2jQ@mail.gmail.com

Author: alvherre

doc/src/sgml/ref/alter_table.sgml

@@ -486,8 +486,6 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
      <para>
       Additional restrictions apply when unique or primary key constraints
       are added to partitioned tables; see <link linkend="sql-createtable"><command>CREATE TABLE</command></link>.
-      Also, foreign key constraints on partitioned
-      tables may not be declared <literal>NOT VALID</literal> at present.
      </para>
 
     </listitem>

src/backend/commands/tablecmds.c

@@ -574,8 +574,9 @@ static void createForeignKeyActionTriggers(Relation rel, Oid refRelOid,
 										   Oid indexOid,
 										   Oid parentDelTrigger, Oid parentUpdTrigger,
 										   Oid *deleteTrigOid, Oid *updateTrigOid);
-static bool tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
-										 Oid partRelid,
+static bool tryAttachPartitionForeignKey(List **wqueue,
+										 ForeignKeyCacheInfo *fk,
+										 Relation partition,
 										 Oid parentConstrOid, int numfks,
 										 AttrNumber *mapped_conkey, AttrNumber *confkey,
 										 Oid *conpfeqop,
@@ -9772,22 +9773,12 @@ ATAddForeignKeyConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	 * Validity checks (permission checks wait till we have the column
 	 * numbers)
 	 */
-	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
-	{
-		if (!recurse)
-			ereport(ERROR,
-					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("cannot use ONLY for foreign key on partitioned table \"%s\" referencing relation \"%s\"",
-							RelationGetRelationName(rel),
-							RelationGetRelationName(pkrel))));
-		if (fkconstraint->skip_validation && !fkconstraint->initially_valid)
-			ereport(ERROR,
-					(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-					 errmsg("cannot add NOT VALID foreign key on partitioned table \"%s\" referencing relation \"%s\"",
-							RelationGetRelationName(rel),
-							RelationGetRelationName(pkrel)),
-					 errdetail("This feature is not yet supported on partitioned tables.")));
-	}
+	if (!recurse && rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
+		ereport(ERROR,
+				errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				errmsg("cannot use ONLY for foreign key on partitioned table \"%s\" referencing relation \"%s\"",
+					   RelationGetRelationName(rel),
+					   RelationGetRelationName(pkrel)));
 
 	if (pkrel->rd_rel->relkind != RELKIND_RELATION &&
 		pkrel->rd_rel->relkind != RELKIND_PARTITIONED_TABLE)
@@ -10782,14 +10773,12 @@ addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
 		 */
 		for (int i = 0; i < pd->nparts; i++)
 		{
-			Oid			partitionId = pd->oids[i];
-			Relation	partition = table_open(partitionId, lockmode);
+			Relation	partition = table_open(pd->oids[i], lockmode);
 			List	   *partFKs;
 			AttrMap    *attmap;
 			AttrNumber	mapped_fkattnum[INDEX_MAX_KEYS];
 			bool		attached;
 			ObjectAddress address;
-			ListCell   *cell;
 
 			CheckAlterTableIsSafe(partition);
 
@@ -10802,13 +10791,11 @@ addFkRecurseReferencing(List **wqueue, Constraint *fkconstraint, Relation rel,
 			/* Check whether an existing constraint can be repurposed */
 			partFKs = copyObject(RelationGetFKeyList(partition));
 			attached = false;
-			foreach(cell, partFKs)
+			foreach_node(ForeignKeyCacheInfo, fk, partFKs)
 			{
-				ForeignKeyCacheInfo *fk;
-
-				fk = lfirst_node(ForeignKeyCacheInfo, cell);
-				if (tryAttachPartitionForeignKey(fk,
-												 partitionId,
+				if (tryAttachPartitionForeignKey(wqueue,
+												 fk,
+												 partition,
 												 parentConstr,
 												 numfks,
 												 mapped_fkattnum,
@@ -11260,8 +11247,9 @@ CloneFkReferencing(List **wqueue, Relation parentRel, Relation partRel)
 		{
 			ForeignKeyCacheInfo *fk = lfirst_node(ForeignKeyCacheInfo, lc);
 
-			if (tryAttachPartitionForeignKey(fk,
-											 RelationGetRelid(partRel),
+			if (tryAttachPartitionForeignKey(wqueue,
+											 fk,
+											 partRel,
 											 parentConstrOid,
 											 numfks,
 											 mapped_conkey,
@@ -11364,8 +11352,9 @@ CloneFkReferencing(List **wqueue, Relation parentRel, Relation partRel)
  * return false.
  */
 static bool
-tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
-							 Oid partRelid,
+tryAttachPartitionForeignKey(List **wqueue,
+							 ForeignKeyCacheInfo *fk,
+							 Relation partition,
 							 Oid parentConstrOid,
 							 int numfks,
 							 AttrNumber *mapped_conkey,
@@ -11379,6 +11368,7 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 	Form_pg_constraint parentConstr;
 	HeapTuple	partcontup;
 	Form_pg_constraint partConstr;
+	bool		queueValidation;
 	ScanKeyData key;
 	SysScanDesc scan;
 	HeapTuple	trigtup;
@@ -11411,18 +11401,12 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 		}
 	}
 
-	/*
-	 * Looks good so far; do some more extensive checks.  Presumably the check
-	 * for 'convalidated' could be dropped, since we don't really care about
-	 * that, but let's be careful for now.
-	 */
-	partcontup = SearchSysCache1(CONSTROID,
-								 ObjectIdGetDatum(fk->conoid));
+	/* Looks good so far; perform more extensive checks. */
+	partcontup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
 	if (!HeapTupleIsValid(partcontup))
 		elog(ERROR, "cache lookup failed for constraint %u", fk->conoid);
 	partConstr = (Form_pg_constraint) GETSTRUCT(partcontup);
 	if (OidIsValid(partConstr->conparentid) ||
-		!partConstr->convalidated ||
 		partConstr->condeferrable != parentConstr->condeferrable ||
 		partConstr->condeferred != parentConstr->condeferred ||
 		partConstr->confupdtype != parentConstr->confupdtype ||
@@ -11434,6 +11418,13 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 		return false;
 	}
 
+	/*
+	 * Will we need to validate this constraint?   A valid parent constraint
+	 * implies that all child constraints have been validated, so if this one
+	 * isn't, we must trigger phase 3 validation.
+	 */
+	queueValidation = parentConstr->convalidated && !partConstr->convalidated;
+
 	ReleaseSysCache(partcontup);
 	ReleaseSysCache(parentConstrTup);
 
@@ -11481,7 +11472,8 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 
 	systable_endscan(scan);
 
-	ConstraintSetParentConstraint(fk->conoid, parentConstrOid, partRelid);
+	ConstraintSetParentConstraint(fk->conoid, parentConstrOid,
+								  RelationGetRelid(partition));
 
 	/*
 	 * Like the constraint, attach partition's "check" triggers to the
@@ -11492,10 +11484,10 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 							   &insertTriggerOid, &updateTriggerOid);
 	Assert(OidIsValid(insertTriggerOid) && OidIsValid(parentInsTrigger));
 	TriggerSetParentTrigger(trigrel, insertTriggerOid, parentInsTrigger,
-							partRelid);
+							RelationGetRelid(partition));
 	Assert(OidIsValid(updateTriggerOid) && OidIsValid(parentUpdTrigger));
 	TriggerSetParentTrigger(trigrel, updateTriggerOid, parentUpdTrigger,
-							partRelid);
+							RelationGetRelid(partition));
 
 	/*
 	 * If the referenced table is partitioned, then the partition we're
@@ -11572,7 +11564,33 @@ tryAttachPartitionForeignKey(ForeignKeyCacheInfo *fk,
 		table_close(pg_constraint, RowShareLock);
 	}
 
-	CommandCounterIncrement();
+	/* If validation is needed, put it in the queue now. */
+	if (queueValidation)
+	{
+		Relation	conrel;
+
+		/*
+		 * We updated this pg_constraint row above to set its parent;
+		 * validating it will cause its convalidated flag to change, so we
+		 * need CCI here.  XXX it might work better to effect the convalidated
+		 * changes for all constraints together during phase 3, but that
+		 * requires more invasive code surgery.
+		 */
+		CommandCounterIncrement();
+
+		conrel = table_open(ConstraintRelationId, RowExclusiveLock);
+
+		partcontup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fk->conoid));
+		if (!HeapTupleIsValid(partcontup))
+			elog(ERROR, "cache lookup failed for constraint %u", fk->conoid);
+
+		/* Use the same lock as for AT_ValidateConstraint */
+		QueueFKConstraintValidation(wqueue, conrel, partition, partcontup,
+									ShareUpdateExclusiveLock);
+		ReleaseSysCache(partcontup);
+		table_close(conrel, RowExclusiveLock);
+	}
+
 	return true;
 }
 
@@ -12113,7 +12131,7 @@ ATExecValidateConstraint(List **wqueue, Relation rel, char *constrName,
  *
  * Add an entry to the wqueue to validate the given foreign key constraint in
  * Phase 3 and update the convalidated field in the pg_constraint catalog
- * for the specified relation.
+ * for the specified relation and all its children.
  */
 static void
 QueueFKConstraintValidation(List **wqueue, Relation conrel, Relation rel,
@@ -12126,6 +12144,7 @@ QueueFKConstraintValidation(List **wqueue, Relation conrel, Relation rel,
 
 	con = (Form_pg_constraint) GETSTRUCT(contuple);
 	Assert(con->contype == CONSTRAINT_FOREIGN);
+	Assert(!con->convalidated);
 
 	if (rel->rd_rel->relkind == RELKIND_RELATION)
 	{
@@ -12151,9 +12170,48 @@ QueueFKConstraintValidation(List **wqueue, Relation conrel, Relation rel,
 	}
 
 	/*
-	 * We disallow creating invalid foreign keys to or from partitioned
-	 * tables, so ignoring the recursion bit is okay.
+	 * 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 constraint.
 	 */
+	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
+		get_rel_relkind(con->confrelid) == RELKIND_PARTITIONED_TABLE)
+	{
+		ScanKeyData pkey;
+		SysScanDesc pscan;
+		HeapTuple	childtup;
+
+		ScanKeyInit(&pkey,
+					Anum_pg_constraint_conparentid,
+					BTEqualStrategyNumber, F_OIDEQ,
+					ObjectIdGetDatum(con->oid));
+
+		pscan = systable_beginscan(conrel, ConstraintParentIndexId,
+								   true, NULL, 1, &pkey);
+
+		while (HeapTupleIsValid(childtup = systable_getnext(pscan)))
+		{
+			Form_pg_constraint childcon;
+			Relation	childrel;
+
+			childcon = (Form_pg_constraint) GETSTRUCT(childtup);
+
+			/*
+			 * If the child constraint has already been validated, no further
+			 * action is required for it or its descendants, as they are all
+			 * valid.
+			 */
+			if (childcon->convalidated)
+				continue;
+
+			childrel = table_open(childcon->conrelid, lockmode);
+
+			QueueFKConstraintValidation(wqueue, conrel, childrel, childtup,
+										lockmode);
+			table_close(childrel, NoLock);
+		}
+
+		systable_endscan(pscan);
+	}
 
 	/*
 	 * Now update the catalog, while we have the door open.

src/test/regress/expected/foreign_key.out

@@ -1597,12 +1597,6 @@ ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_3
 ALTER TABLE ONLY fk_partitioned_fk ADD FOREIGN KEY (a, b)
   REFERENCES fk_notpartitioned_pk;
 ERROR:  cannot use ONLY for foreign key on partitioned table "fk_partitioned_fk" referencing relation "fk_notpartitioned_pk"
--- Adding a NOT VALID foreign key on a partitioned table referencing
--- a non-partitioned table fails.
-ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b)
-  REFERENCES fk_notpartitioned_pk NOT VALID;
-ERROR:  cannot add NOT VALID foreign key on partitioned table "fk_partitioned_fk" referencing relation "fk_notpartitioned_pk"
-DETAIL:  This feature is not yet supported on partitioned tables.
 -- these inserts, targeting both the partition directly as well as the
 -- partitioned table, should all fail
 INSERT INTO fk_partitioned_fk (a,b) VALUES (500, 501);
@@ -1680,6 +1674,97 @@ DELETE FROM fk_notpartitioned_pk WHERE a = 1;
 ERROR:  update or delete on table "fk_notpartitioned_pk" violates foreign key constraint "fk_partitioned_fk_a_fkey" on table "fk_partitioned_fk"
 DETAIL:  Key (a)=(1) is still referenced from table "fk_partitioned_fk".
 DROP TABLE fk_notpartitioned_pk, fk_partitioned_fk;
+-- NOT VALID foreign keys on partitioned table
+CREATE TABLE fk_notpartitioned_pk (a int, b int, PRIMARY KEY (a, b));
+CREATE TABLE fk_partitioned_fk (b int, a int) PARTITION BY RANGE (a, b);
+ALTER TABLE fk_partitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT VALID;
+-- Attaching a child table with the same valid foreign key constraint.
+CREATE TABLE fk_partitioned_fk_1 (a int, b int);
+ALTER TABLE fk_partitioned_fk_1 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_1 FOR VALUES FROM (0,0) TO (1000,1000);
+-- Child constraint will remain valid.
+SELECT conname, convalidated, conrelid::regclass FROM pg_constraint
+WHERE conrelid::regclass::text like 'fk_partitioned_fk%' ORDER BY oid;
+           conname            | convalidated |      conrelid       
+------------------------------+--------------+---------------------
+ fk_partitioned_fk_a_b_fkey   | f            | fk_partitioned_fk
+ fk_partitioned_fk_1_a_b_fkey | t            | fk_partitioned_fk_1
+(2 rows)
+
+-- Validate the constraint
+ALTER TABLE fk_partitioned_fk VALIDATE CONSTRAINT fk_partitioned_fk_a_b_fkey;
+-- All constraints are now valid.
+SELECT conname, convalidated, conrelid::regclass FROM pg_constraint
+WHERE conrelid::regclass::text like 'fk_partitioned_fk%' ORDER BY oid;
+           conname            | convalidated |      conrelid       
+------------------------------+--------------+---------------------
+ fk_partitioned_fk_a_b_fkey   | t            | fk_partitioned_fk
+ fk_partitioned_fk_1_a_b_fkey | t            | fk_partitioned_fk_1
+(2 rows)
+
+-- Attaching a child with a NOT VALID constraint.
+CREATE TABLE fk_partitioned_fk_2 (a int, b int);
+INSERT INTO fk_partitioned_fk_2 VALUES(1000, 1000); -- doesn't exist in referenced table
+ALTER TABLE fk_partitioned_fk_2 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT VALID;
+-- It will fail because the attach operation implicitly validates the data.
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES FROM (1000,1000) TO (2000,2000);
+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)=(1000, 1000) is not present in table "fk_notpartitioned_pk".
+-- Remove the invalid data and try again.
+TRUNCATE fk_partitioned_fk_2;
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_2 FOR VALUES FROM (1000,1000) TO (2000,2000);
+-- The child constraint will also be valid.
+SELECT conname, convalidated FROM pg_constraint WHERE conrelid = 'fk_partitioned_fk_2'::regclass;
+           conname            | convalidated 
+------------------------------+--------------
+ fk_partitioned_fk_2_a_b_fkey | t
+(1 row)
+
+-- Test case where the child constraint is invalid, the grandchild constraint
+-- is valid, and the validation for the grandchild should be skipped when a
+-- valid constraint is applied to the top parent.
+CREATE TABLE fk_partitioned_fk_3 (a int, b int) PARTITION BY RANGE (a, b);
+ALTER TABLE fk_partitioned_fk_3 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk NOT VALID;
+CREATE TABLE fk_partitioned_fk_3_1 (a int, b int);
+ALTER TABLE fk_partitioned_fk_3_1 ADD FOREIGN KEY (a, b) REFERENCES fk_notpartitioned_pk;
+ALTER TABLE fk_partitioned_fk_3 ATTACH PARTITION fk_partitioned_fk_3_1 FOR VALUES FROM (2000,2000) TO (3000,3000);
+ALTER TABLE fk_partitioned_fk ATTACH PARTITION fk_partitioned_fk_3 FOR VALUES FROM (2000,2000) TO (3000,3000);
+-- All constraints are now valid.
+SELECT conname, convalidated, conrelid::regclass FROM pg_constraint
+WHERE conrelid::regclass::text like 'fk_partitioned_fk%' ORDER BY oid;
+            conname             | convalidated |       conrelid        
+--------------------------------+--------------+-----------------------
+ fk_partitioned_fk_a_b_fkey     | t            | fk_partitioned_fk
+ fk_partitioned_fk_1_a_b_fkey   | t            | fk_partitioned_fk_1
+ fk_partitioned_fk_2_a_b_fkey   | t            | fk_partitioned_fk_2
+ fk_partitioned_fk_3_a_b_fkey   | t            | fk_partitioned_fk_3
+ fk_partitioned_fk_3_1_a_b_fkey | t            | fk_partitioned_fk_3_1
+(5 rows)
+
+DROP TABLE fk_partitioned_fk, fk_notpartitioned_pk;
+-- NOT VALID foreign key on a non-partitioned table referencing a partitioned table
+CREATE TABLE fk_partitioned_pk (a int, b int, PRIMARY KEY (a, b)) PARTITION BY RANGE (a, b);
+CREATE TABLE fk_partitioned_pk_1 PARTITION OF fk_partitioned_pk FOR VALUES FROM (0,0) TO (1000,1000);
+CREATE TABLE fk_notpartitioned_fk (b int, a int);
+ALTER TABLE fk_notpartitioned_fk ADD FOREIGN KEY (a, b) REFERENCES fk_partitioned_pk NOT VALID;
+-- Constraint will be invalid.
+SELECT conname, convalidated FROM pg_constraint WHERE conrelid = 'fk_notpartitioned_fk'::regclass;
+            conname             | convalidated 
+--------------------------------+--------------
+ fk_notpartitioned_fk_a_b_fkey  | f
+ fk_notpartitioned_fk_a_b_fkey1 | f
+(2 rows)
+
+ALTER TABLE fk_notpartitioned_fk VALIDATE CONSTRAINT fk_notpartitioned_fk_a_b_fkey;
+-- All constraints are now valid.
+SELECT conname, convalidated FROM pg_constraint WHERE conrelid = 'fk_notpartitioned_fk'::regclass;
+            conname             | convalidated 
+--------------------------------+--------------
+ fk_notpartitioned_fk_a_b_fkey  | t
+ fk_notpartitioned_fk_a_b_fkey1 | t
+(2 rows)
+
+DROP TABLE fk_notpartitioned_fk, fk_partitioned_pk;
 -- Test some other exotic foreign key features: MATCH SIMPLE, ON UPDATE/DELETE
 -- actions
 CREATE TABLE fk_notpartitioned_pk (a int, b int, primary key (a, b));