Support domains over composite types.

This is the last major omission in our domains feature: you can now
make a domain over anything that's not a pseudotype.

The major complication from an implementation standpoint is that places
that might be creating tuples of a domain type now need to be prepared
to apply domain_check().  It seems better that unprepared code fail
with an error like "<type> is not composite" than that it silently fail
to apply domain constraints.  Therefore, relevant infrastructure like
get_func_result_type() and lookup_rowtype_tupdesc() has been adjusted
to treat domain-over-composite as a distinct case that unprepared code
won't recognize, rather than just transparently treating it the same
as plain composite.  This isn't a 100% solution to the possibility of
overlooked domain checks, but it catches most places.

In passing, improve typcache.c's support for domains (it can now cache
the identity of a domain's base type), and rewrite the argument handling
logic in jsonfuncs.c's populate_record[set]_worker to reduce duplicative
per-call lookups.

I believe this is code-complete so far as the core and contrib code go.
The PLs need varying amounts of work, which will be tackled in followup
patches.

Discussion: https://postgr.es/m/[email protected]

1 files changed, 16 insertions, 2 deletions

diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index b7a14dc87e1..48961e31aa9 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -2398,12 +2398,26 @@ get_typtype(Oid typid)
  * type_is_rowtype
  *
  *		Convenience function to determine whether a type OID represents
- *		a "rowtype" type --- either RECORD or a named composite type.
+ *		a "rowtype" type --- either RECORD or a named composite type
+ *		(including a domain over a named composite type).
  */
 bool
 type_is_rowtype(Oid typid)
 {
-	return (typid == RECORDOID || get_typtype(typid) == TYPTYPE_COMPOSITE);
+	if (typid == RECORDOID)
+		return true;			/* easy case */
+	switch (get_typtype(typid))
+	{
+		case TYPTYPE_COMPOSITE:
+			return true;
+		case TYPTYPE_DOMAIN:
+			if (get_typtype(getBaseType(typid)) == TYPTYPE_COMPOSITE)
+				return true;
+			break;
+		default:
+			break;
+	}
+	return false;
 }
 
 /*