Refactor duplicate code into DeconstructFkConstraintRow

My commit 3de241dba86f introduced some code (in tablecmds.c) to obtain
data from a pg_constraint row for a foreign key, that already existed in
ri_triggers.c.  Split it out into its own routine in pg_constraint.c,
where it naturally belongs.

No functional code changes, only code movement.

Backpatch to pg11, because a future bugfix is simpler after this.

src/backend/catalog/pg_constraint.c

@@ -446,14 +446,11 @@ static void
 clone_fk_constraints(Relation pg_constraint, Relation parentRel,
 					 Relation partRel, List *clone, List **cloned)
 {
-	TupleDesc	tupdesc;
 	AttrNumber *attmap;
 	List	   *partFKs;
 	List	   *subclone = NIL;
 	ListCell   *cell;
 
-	tupdesc = RelationGetDescr(pg_constraint);
-
 	/*
 	 * The constraint key may differ, if the columns in the partition are
 	 * different.  This map is used to convert them.
@@ -483,9 +480,6 @@ clone_fk_constraints(Relation pg_constraint, Relation parentRel,
 		int			nelem;
 		ListCell   *cell;
 		int			i;
-		ArrayType  *arr;
-		Datum		datum;
-		bool		isnull;
 
 		tuple = SearchSysCache1(CONSTROID, parentConstrOid);
 		if (!tuple)
@@ -502,93 +496,11 @@ clone_fk_constraints(Relation pg_constraint, Relation parentRel,
 
 		ObjectAddressSet(parentAddr, ConstraintRelationId, parentConstrOid);
 
-		datum = fastgetattr(tuple, Anum_pg_constraint_conkey,
+		DeconstructFkConstraintRow(tuple, &nelem, conkey, confkey,
-							tupdesc, &isnull);
+								   conpfeqop, conppeqop, conffeqop);
-		if (isnull)
-			elog(ERROR, "null conkey");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != INT2OID)
-			elog(ERROR, "conkey is not a 1-D smallint array");
-		memcpy(conkey, ARR_DATA_PTR(arr), nelem * sizeof(AttrNumber));
-
 		for (i = 0; i < nelem; i++)
 			mapped_conkey[i] = attmap[conkey[i] - 1];
 
-		datum = fastgetattr(tuple, Anum_pg_constraint_confkey,
-							tupdesc, &isnull);
-		if (isnull)
-			elog(ERROR, "null confkey");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != INT2OID)
-			elog(ERROR, "confkey is not a 1-D smallint array");
-		memcpy(confkey, ARR_DATA_PTR(arr), nelem * sizeof(AttrNumber));
-
-		datum = fastgetattr(tuple, Anum_pg_constraint_conpfeqop,
-							tupdesc, &isnull);
-		if (isnull)
-			elog(ERROR, "null conpfeqop");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != OIDOID)
-			elog(ERROR, "conpfeqop is not a 1-D OID array");
-		memcpy(conpfeqop, ARR_DATA_PTR(arr), nelem * sizeof(Oid));
-
-		datum = fastgetattr(tuple, Anum_pg_constraint_conpfeqop,
-							tupdesc, &isnull);
-		if (isnull)
-			elog(ERROR, "null conpfeqop");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != OIDOID)
-			elog(ERROR, "conpfeqop is not a 1-D OID array");
-		memcpy(conpfeqop, ARR_DATA_PTR(arr), nelem * sizeof(Oid));
-
-		datum = fastgetattr(tuple, Anum_pg_constraint_conppeqop,
-							tupdesc, &isnull);
-		if (isnull)
-			elog(ERROR, "null conppeqop");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != OIDOID)
-			elog(ERROR, "conppeqop is not a 1-D OID array");
-		memcpy(conppeqop, ARR_DATA_PTR(arr), nelem * sizeof(Oid));
-
-		datum = fastgetattr(tuple, Anum_pg_constraint_conffeqop,
-							tupdesc, &isnull);
-		if (isnull)
-			elog(ERROR, "null conffeqop");
-		arr = DatumGetArrayTypeP(datum);
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != OIDOID)
-			elog(ERROR, "conffeqop is not a 1-D OID array");
-		memcpy(conffeqop, ARR_DATA_PTR(arr), nelem * sizeof(Oid));
-
 		/*
 		 * Before creating a new constraint, see whether any existing FKs are
 		 * fit for the purpose.  If one is, attach the parent constraint to it,
@@ -1530,6 +1442,115 @@ get_primary_key_attnos(Oid relid, bool deferrableOk, Oid *constraintOid)
 	return pkattnos;
 }
 
+/*
+ * Extract data from the pg_constraint tuple of a foreign-key constraint.
+ *
+ * All arguments save the first are output arguments; the last three of them
+ * can be passed as NULL if caller doesn't need them.
+ */
+void
+DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
+						   AttrNumber *conkey, AttrNumber *confkey,
+						   Oid *pf_eq_oprs, Oid *pp_eq_oprs, Oid *ff_eq_oprs)
+{
+	Oid			constrId;
+	Datum		adatum;
+	bool		isNull;
+	ArrayType  *arr;
+	int			numkeys;
+
+	constrId = ((Form_pg_constraint) GETSTRUCT(tuple))->oid;
+
+	/*
+	 * We expect the arrays to be 1-D arrays of the right types; verify that.
+	 * We don't need to use deconstruct_array() since the array data is just
+	 * going to look like a C array of values.
+	 */
+	adatum = SysCacheGetAttr(CONSTROID, tuple,
+							 Anum_pg_constraint_conkey, &isNull);
+	if (isNull)
+		elog(ERROR, "null conkey for constraint %u", constrId);
+	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
+	if (ARR_NDIM(arr) != 1 ||
+		ARR_HASNULL(arr) ||
+		ARR_ELEMTYPE(arr) != INT2OID)
+		elog(ERROR, "conkey is not a 1-D smallint array");
+	numkeys = ARR_DIMS(arr)[0];
+	if (numkeys <= 0 || numkeys > INDEX_MAX_KEYS)
+		elog(ERROR, "foreign key constraint cannot have %d columns", numkeys);
+	memcpy(conkey, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
+	if ((Pointer) arr != DatumGetPointer(adatum))
+		pfree(arr);				/* free de-toasted copy, if any */
+
+	adatum = SysCacheGetAttr(CONSTROID, tuple,
+							 Anum_pg_constraint_confkey, &isNull);
+	if (isNull)
+		elog(ERROR, "null confkey for constraint %u", constrId);
+	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
+	if (ARR_NDIM(arr) != 1 ||
+		ARR_DIMS(arr)[0] != numkeys ||
+		ARR_HASNULL(arr) ||
+		ARR_ELEMTYPE(arr) != INT2OID)
+		elog(ERROR, "confkey is not a 1-D smallint array");
+	memcpy(confkey, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
+	if ((Pointer) arr != DatumGetPointer(adatum))
+		pfree(arr);				/* free de-toasted copy, if any */
+
+	if (pf_eq_oprs)
+	{
+		adatum = SysCacheGetAttr(CONSTROID, tuple,
+								 Anum_pg_constraint_conpfeqop, &isNull);
+		if (isNull)
+			elog(ERROR, "null conpfeqop for constraint %u", constrId);
+		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
+		/* see TryReuseForeignKey if you change the test below */
+		if (ARR_NDIM(arr) != 1 ||
+			ARR_DIMS(arr)[0] != numkeys ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != OIDOID)
+			elog(ERROR, "conpfeqop is not a 1-D Oid array");
+		memcpy(pf_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
+		if ((Pointer) arr != DatumGetPointer(adatum))
+			pfree(arr);			/* free de-toasted copy, if any */
+	}
+
+	if (pp_eq_oprs)
+	{
+		adatum = SysCacheGetAttr(CONSTROID, tuple,
+								 Anum_pg_constraint_conppeqop, &isNull);
+		if (isNull)
+			elog(ERROR, "null conppeqop for constraint %u", constrId);
+		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
+		if (ARR_NDIM(arr) != 1 ||
+			ARR_DIMS(arr)[0] != numkeys ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != OIDOID)
+			elog(ERROR, "conppeqop is not a 1-D Oid array");
+		memcpy(pp_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
+		if ((Pointer) arr != DatumGetPointer(adatum))
+			pfree(arr);			/* free de-toasted copy, if any */
+	}
+
+	if (ff_eq_oprs)
+	{
+		adatum = SysCacheGetAttr(CONSTROID, tuple,
+								 Anum_pg_constraint_conffeqop, &isNull);
+		if (isNull)
+			elog(ERROR, "null conffeqop for constraint %u", constrId);
+		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
+		if (ARR_NDIM(arr) != 1 ||
+			ARR_DIMS(arr)[0] != numkeys ||
+			ARR_HASNULL(arr) ||
+			ARR_ELEMTYPE(arr) != OIDOID)
+			elog(ERROR, "conffeqop is not a 1-D Oid array");
+		memcpy(ff_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
+		if ((Pointer) arr != DatumGetPointer(adatum))
+			pfree(arr);			/* free de-toasted copy, if any */
+	}
+
+	*numfks = numkeys;
+}
+
 /*
  * Determine whether a relation can be proven functionally dependent on
  * a set of grouping columns.  If so, return true and add the pg_constraint

src/backend/utils/adt/ri_triggers.c

@@ -2189,10 +2189,6 @@ ri_LoadConstraintInfo(Oid constraintOid)
 	bool		found;
 	HeapTuple	tup;
 	Form_pg_constraint conForm;
-	Datum		adatum;
-	bool		isNull;
-	ArrayType  *arr;
-	int			numkeys;
 
 	/*
 	 * On the first call initialize the hashtable
@@ -2234,84 +2230,13 @@ ri_LoadConstraintInfo(Oid constraintOid)
 	riinfo->confdeltype = conForm->confdeltype;
 	riinfo->confmatchtype = conForm->confmatchtype;
 
-	/*
+	DeconstructFkConstraintRow(tup,
-	 * We expect the arrays to be 1-D arrays of the right types; verify that.
+							   &riinfo->nkeys,
-	 * We don't need to use deconstruct_array() since the array data is just
+							   riinfo->fk_attnums,
-	 * going to look like a C array of values.
+							   riinfo->pk_attnums,
-	 */
+							   riinfo->pf_eq_oprs,
-	adatum = SysCacheGetAttr(CONSTROID, tup,
+							   riinfo->pp_eq_oprs,
-							 Anum_pg_constraint_conkey, &isNull);
+							   riinfo->ff_eq_oprs);
-	if (isNull)
-		elog(ERROR, "null conkey for constraint %u", constraintOid);
-	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-	if (ARR_NDIM(arr) != 1 ||
-		ARR_HASNULL(arr) ||
-		ARR_ELEMTYPE(arr) != INT2OID)
-		elog(ERROR, "conkey is not a 1-D smallint array");
-	numkeys = ARR_DIMS(arr)[0];
-	if (numkeys <= 0 || numkeys > RI_MAX_NUMKEYS)
-		elog(ERROR, "foreign key constraint cannot have %d columns", numkeys);
-	riinfo->nkeys = numkeys;
-	memcpy(riinfo->fk_attnums, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
-	if ((Pointer) arr != DatumGetPointer(adatum))
-		pfree(arr);				/* free de-toasted copy, if any */
-
-	adatum = SysCacheGetAttr(CONSTROID, tup,
-							 Anum_pg_constraint_confkey, &isNull);
-	if (isNull)
-		elog(ERROR, "null confkey for constraint %u", constraintOid);
-	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-	if (ARR_NDIM(arr) != 1 ||
-		ARR_DIMS(arr)[0] != numkeys ||
-		ARR_HASNULL(arr) ||
-		ARR_ELEMTYPE(arr) != INT2OID)
-		elog(ERROR, "confkey is not a 1-D smallint array");
-	memcpy(riinfo->pk_attnums, ARR_DATA_PTR(arr), numkeys * sizeof(int16));
-	if ((Pointer) arr != DatumGetPointer(adatum))
-		pfree(arr);				/* free de-toasted copy, if any */
-
-	adatum = SysCacheGetAttr(CONSTROID, tup,
-							 Anum_pg_constraint_conpfeqop, &isNull);
-	if (isNull)
-		elog(ERROR, "null conpfeqop for constraint %u", constraintOid);
-	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-	/* see TryReuseForeignKey if you change the test below */
-	if (ARR_NDIM(arr) != 1 ||
-		ARR_DIMS(arr)[0] != numkeys ||
-		ARR_HASNULL(arr) ||
-		ARR_ELEMTYPE(arr) != OIDOID)
-		elog(ERROR, "conpfeqop is not a 1-D Oid array");
-	memcpy(riinfo->pf_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
-	if ((Pointer) arr != DatumGetPointer(adatum))
-		pfree(arr);				/* free de-toasted copy, if any */
-
-	adatum = SysCacheGetAttr(CONSTROID, tup,
-							 Anum_pg_constraint_conppeqop, &isNull);
-	if (isNull)
-		elog(ERROR, "null conppeqop for constraint %u", constraintOid);
-	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-	if (ARR_NDIM(arr) != 1 ||
-		ARR_DIMS(arr)[0] != numkeys ||
-		ARR_HASNULL(arr) ||
-		ARR_ELEMTYPE(arr) != OIDOID)
-		elog(ERROR, "conppeqop is not a 1-D Oid array");
-	memcpy(riinfo->pp_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
-	if ((Pointer) arr != DatumGetPointer(adatum))
-		pfree(arr);				/* free de-toasted copy, if any */
-
-	adatum = SysCacheGetAttr(CONSTROID, tup,
-							 Anum_pg_constraint_conffeqop, &isNull);
-	if (isNull)
-		elog(ERROR, "null conffeqop for constraint %u", constraintOid);
-	arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-	if (ARR_NDIM(arr) != 1 ||
-		ARR_DIMS(arr)[0] != numkeys ||
-		ARR_HASNULL(arr) ||
-		ARR_ELEMTYPE(arr) != OIDOID)
-		elog(ERROR, "conffeqop is not a 1-D Oid array");
-	memcpy(riinfo->ff_eq_oprs, ARR_DATA_PTR(arr), numkeys * sizeof(Oid));
-	if ((Pointer) arr != DatumGetPointer(adatum))
-		pfree(arr);				/* free de-toasted copy, if any */
 
 	ReleaseSysCache(tup);
 

src/backend/utils/cache/relcache.c

@@ -4125,10 +4125,6 @@ RelationGetFKeyList(Relation relation)
 	{
 		Form_pg_constraint constraint = (Form_pg_constraint) GETSTRUCT(htup);
 		ForeignKeyCacheInfo *info;
-		Datum		adatum;
-		bool		isnull;
-		ArrayType  *arr;
-		int			nelem;
 
 		/* consider only foreign keys */
 		if (constraint->contype != CONSTRAINT_FOREIGN)
@@ -4139,58 +4135,11 @@ RelationGetFKeyList(Relation relation)
 		info->conrelid = constraint->conrelid;
 		info->confrelid = constraint->confrelid;
 
-		/* Extract data from conkey field */
+		DeconstructFkConstraintRow(htup, &info->nkeys,
-		adatum = fastgetattr(htup, Anum_pg_constraint_conkey,
+								   info->conkey,
-							 conrel->rd_att, &isnull);
+								   info->confkey,
-		if (isnull)
+								   info->conpfeqop,
-			elog(ERROR, "null conkey for rel %s",
+								   NULL, NULL);
-				 RelationGetRelationName(relation));
-
-		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem < 1 ||
-			nelem > INDEX_MAX_KEYS ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != INT2OID)
-			elog(ERROR, "conkey is not a 1-D smallint array");
-
-		info->nkeys = nelem;
-		memcpy(info->conkey, ARR_DATA_PTR(arr), nelem * sizeof(AttrNumber));
-
-		/* Likewise for confkey */
-		adatum = fastgetattr(htup, Anum_pg_constraint_confkey,
-							 conrel->rd_att, &isnull);
-		if (isnull)
-			elog(ERROR, "null confkey for rel %s",
-				 RelationGetRelationName(relation));
-
-		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem != info->nkeys ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != INT2OID)
-			elog(ERROR, "confkey is not a 1-D smallint array");
-
-		memcpy(info->confkey, ARR_DATA_PTR(arr), nelem * sizeof(AttrNumber));
-
-		/* Likewise for conpfeqop */
-		adatum = fastgetattr(htup, Anum_pg_constraint_conpfeqop,
-							 conrel->rd_att, &isnull);
-		if (isnull)
-			elog(ERROR, "null conpfeqop for rel %s",
-				 RelationGetRelationName(relation));
-
-		arr = DatumGetArrayTypeP(adatum);	/* ensure not toasted */
-		nelem = ARR_DIMS(arr)[0];
-		if (ARR_NDIM(arr) != 1 ||
-			nelem != info->nkeys ||
-			ARR_HASNULL(arr) ||
-			ARR_ELEMTYPE(arr) != OIDOID)
-			elog(ERROR, "conpfeqop is not a 1-D OID array");
-
-		memcpy(info->conpfeqop, ARR_DATA_PTR(arr), nelem * sizeof(Oid));
 
 		/* Add FK's node to the result list */
 		result = lappend(result, info);

src/include/catalog/pg_constraint.h

@@ -251,6 +251,9 @@ extern Oid	get_relation_idx_constraint_oid(Oid relationId, Oid indexId);
 
 extern Bitmapset *get_primary_key_attnos(Oid relid, bool deferrableOk,
 					   Oid *constraintOid);
+extern void DeconstructFkConstraintRow(HeapTuple tuple, int *numfks,
+						   AttrNumber *conkey, AttrNumber *confkey,
+						   Oid *pf_eq_oprs, Oid *pp_eq_oprs, Oid *ff_eq_oprs);
 
 extern bool check_functional_grouping(Oid relid,
 						  Index varno, Index varlevelsup,