refactor: split ATExecAlterConstrRecurse()

This splits out a couple of subroutines from
ATExecAlterConstrRecurse().  This makes the main function a bit
smaller, and a future patch (NOT ENFORCED foreign-key constraints)
will also want to call some of the pieces separately.

Author: Amul Sul <amul.sul@enterprisedb.com>
Reviewed-by: jian he <jian.universality@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAAJ_b962c5AcYW9KUt_R_ER5qs3fUGbe4az-SP-vuwPS-w-AGA%40mail.gmail.com

src/backend/commands/tablecmds.c

@@ -394,6 +394,12 @@ static ObjectAddress ATExecAlterConstraint(Relation rel, AlterTableCmd *cmd,
 static bool ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 									 Relation rel, HeapTuple contuple, List **otherrelids,
 									 LOCKMODE lockmode);
+static void AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
+											bool deferrable, bool initdeferred,
+											List **otherrelids);
+static void ATExecAlterChildConstr(Constraint *cmdcon, Relation conrel, Relation tgrel,
+								   Relation rel, HeapTuple contuple, List **otherrelids,
+								   LOCKMODE lockmode);
 static ObjectAddress ATExecValidateConstraint(List **wqueue,
 											  Relation rel, char *constrName,
 											  bool recurse, bool recursing, LOCKMODE lockmode);
@@ -11861,9 +11867,6 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 	{
 		HeapTuple	copyTuple;
 		Form_pg_constraint copy_con;
-		HeapTuple	tgtuple;
-		ScanKeyData tgkey;
-		SysScanDesc tgscan;
 
 		copyTuple = heap_copytuple(contuple);
 		copy_con = (Form_pg_constraint) GETSTRUCT(copyTuple);
@@ -11884,6 +11887,42 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 		 * Now we need to update the multiple entries in pg_trigger that
 		 * implement the constraint.
 		 */
+		AlterConstrTriggerDeferrability(conoid, tgrel, rel, 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, rel, contuple,
+							   otherrelids, lockmode);
+
+	return changed;
+}
+
+/*
+ * A subroutine of ATExecAlterConstrRecurse that updated constraint trigger's
+ * deferrability.
+ *
+ * The arguments to this function have the same meaning as the arguments to
+ * ATExecAlterConstrRecurse.
+ */
+static void
+AlterConstrTriggerDeferrability(Oid conoid, Relation tgrel, Relation rel,
+								bool deferrable, bool initdeferred,
+								List **otherrelids)
+{
+	HeapTuple	tgtuple;
+	ScanKeyData tgkey;
+	SysScanDesc tgscan;
+
 	ScanKeyInit(&tgkey,
 				Anum_pg_trigger_tgconstraint,
 				BTEqualStrategyNumber, F_OIDEQ,
@@ -11898,19 +11937,19 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 
 		/*
 		 * Remember OIDs of other relation(s) involved in FK constraint.
-			 * (Note: it's likely that we could skip forcing a relcache inval
+		 * (Note: it's likely that we could skip forcing a relcache inval for
-			 * for other rels that don't have a trigger whose properties
+		 * other rels that don't have a trigger whose properties change, but
-			 * change, but let's be conservative.)
+		 * let's be conservative.)
 		 */
 		if (tgform->tgrelid != RelationGetRelid(rel))
 			*otherrelids = list_append_unique_oid(*otherrelids,
 												  tgform->tgrelid);
 
 		/*
-			 * Update deferrability of RI_FKey_noaction_del,
+		 * Update enable status and 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
+		 * triggers, but not others; see createForeignKeyActionTriggers and
-			 * and CreateFKCheckTrigger.
+		 * CreateFKCheckTrigger.
 		 */
 		if (tgform->tgfoid != F_RI_FKEY_NOACTION_DEL &&
 			tgform->tgfoid != F_RI_FKEY_NOACTION_UPD &&
@@ -11921,8 +11960,8 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 		tgCopyTuple = heap_copytuple(tgtuple);
 		copy_tg = (Form_pg_trigger) GETSTRUCT(tgCopyTuple);
 
-			copy_tg->tgdeferrable = cmdcon->deferrable;
+		copy_tg->tgdeferrable = deferrable;
-			copy_tg->tginitdeferred = cmdcon->initdeferred;
+		copy_tg->tginitdeferred = initdeferred;
 		CatalogTupleUpdate(tgrel, &tgCopyTuple->t_self, tgCopyTuple);
 
 		InvokeObjectPostAlterHook(TriggerRelationId, tgform->oid, 0);
@@ -11934,20 +11973,26 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 }
 
 /*
-	 * If the table at either end of the constraint is partitioned, we need to
+ * Invokes ATExecAlterConstrRecurse for each constraint that is a child of the
-	 * recurse and handle every constraint that is a child of this one.
+ * specified constraint.
  *
-	 * (This assumes that the recurse flag is forcibly set for partitioned
+ * The arguments to this function have the same meaning as the arguments to
-	 * tables, and not set for legacy inheritance, though we don't check for
+ * ATExecAlterConstrRecurse.
-	 * that here.)
  */
-	if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE ||
+static void
-		get_rel_relkind(refrelid) == RELKIND_PARTITIONED_TABLE)
+ATExecAlterChildConstr(Constraint *cmdcon, Relation conrel, Relation tgrel,
+					   Relation rel, HeapTuple contuple, List **otherrelids,
+					   LOCKMODE lockmode)
 {
+	Form_pg_constraint currcon;
+	Oid			conoid;
 	ScanKeyData pkey;
 	SysScanDesc pscan;
 	HeapTuple	childtup;
 
+	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
+	conoid = currcon->oid;
+
 	ScanKeyInit(&pkey,
 				Anum_pg_constraint_conparentid,
 				BTEqualStrategyNumber, F_OIDEQ,
@@ -11970,9 +12015,6 @@ ATExecAlterConstrRecurse(Constraint *cmdcon, Relation conrel, Relation tgrel,
 	systable_endscan(pscan);
 }
 
-	return changed;
-}
-
 /*
  * ALTER TABLE VALIDATE CONSTRAINT
  *