Clean up foreign-key caching code in planner.

Coverity complained that the code added by 015e88942a lacked an
error check for SearchSysCache1 failures, which it should have.  But
the code was pretty duff in other ways too, including failure to think
about whether it could really cope with arrays of different lengths.

src/backend/optimizer/util/plancat.c

@@ -408,17 +408,20 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 
 	foreach(l, fkoidlist)
 	{
-		int			i;
-		ArrayType  *arr;
+		Oid			fkoid = lfirst_oid(l);
+		HeapTuple	htup;
+		Form_pg_constraint constraint;
+		ForeignKeyOptInfo *info;
 		Datum		adatum;
 		bool		isnull;
+		ArrayType  *arr;
 		int			numkeys;
-		Oid			fkoid = lfirst_oid(l);
-
-		HeapTuple	htup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fkoid));
-		Form_pg_constraint constraint = (Form_pg_constraint) GETSTRUCT(htup);
+		int			i;
 
-		ForeignKeyOptInfo *info;
+		htup = SearchSysCache1(CONSTROID, ObjectIdGetDatum(fkoid));
+		if (!HeapTupleIsValid(htup)) /* should not happen */
+			elog(ERROR, "cache lookup failed for constraint %u", fkoid);
+		constraint = (Form_pg_constraint) GETSTRUCT(htup);
 
 		Assert(constraint->contype == CONSTRAINT_FOREIGN);
 
@@ -434,8 +437,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 
 		arr = DatumGetArrayTypeP(adatum);
 		numkeys = ARR_DIMS(arr)[0];
-		info->conkeys = (int*)palloc0(numkeys * sizeof(int));
-
+		info->conkeys = (int*)palloc(numkeys * sizeof(int));
 		for (i = 0; i < numkeys; i++)
 			info->conkeys[i] = ((int16 *) ARR_DATA_PTR(arr))[i];
 
@@ -445,9 +447,8 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 		Assert(!isnull);
 
 		arr = DatumGetArrayTypeP(adatum);
-		numkeys = ARR_DIMS(arr)[0];
-		info->confkeys = (int*)palloc0(numkeys * sizeof(int));
-
+		Assert(numkeys == ARR_DIMS(arr)[0]);
+		info->confkeys = (int*)palloc(numkeys * sizeof(int));
 		for (i = 0; i < numkeys; i++)
 			info->confkeys[i] = ((int16 *) ARR_DATA_PTR(arr))[i];
 
@@ -457,9 +458,8 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 		Assert(!isnull);
 
 		arr = DatumGetArrayTypeP(adatum);
-		numkeys = ARR_DIMS(arr)[0];
-		info->conpfeqop = (Oid*)palloc0(numkeys * sizeof(Oid));
-
+		Assert(numkeys == ARR_DIMS(arr)[0]);
+		info->conpfeqop = (Oid*)palloc(numkeys * sizeof(Oid));
 		for (i = 0; i < numkeys; i++)
 			info->conpfeqop[i] = ((Oid *) ARR_DATA_PTR(arr))[i];
 
@@ -467,7 +467,7 @@ get_relation_info(PlannerInfo *root, Oid relationObjectId, bool inhparent,
 
 		ReleaseSysCache(htup);
 
-		fkinfos = lcons(info, fkinfos);
+		fkinfos = lappend(fkinfos, info);
 	}
 
 	list_free(fkoidlist);