Catalog domain not-null constraints

This applies the explicit catalog representation of not-null constraints introduced by b0e96f3 for table constraints also to domain not-null constraints. Reviewed-by: Aleksander Alekseev <[email protected]> Reviewed-by: jian he <[email protected]> Discussion: https://www.postgresql.org/message-id/flat/9ec24d7b-633d-463a-84c6-7acff769c9e8%40eisentraut.org

Author: petere

src/backend/catalog/information_schema.sql

@@ -445,7 +445,7 @@ CREATE VIEW check_constraints AS
 SELECT current_database()::information_schema.sql_identifier AS constraint_catalog,
 rs.nspname::information_schema.sql_identifier AS constraint_schema,
 con.conname::information_schema.sql_identifier AS constraint_name,
-pg_catalog.format('%s IS NOT NULL', at.attname)::information_schema.character_data AS check_clause
+pg_catalog.format('%s IS NOT NULL', coalesce(at.attname, 'VALUE'))::information_schema.character_data AS check_clause
 FROM pg_constraint con
 LEFT JOIN pg_namespace rs ON rs.oid = con.connamespace
 LEFT JOIN pg_class c ON c.oid = con.conrelid

src/backend/catalog/pg_constraint.c

@@ -629,6 +629,50 @@ findNotNullConstraint(Oid relid, const char *colname)
 return findNotNullConstraintAttnum(relid, attnum);
 }
 
+/*
+* Find and return the pg_constraint tuple that implements a validated
+* not-null constraint for the given domain.
+*/
+HeapTuple
+findDomainNotNullConstraint(Oid typid)
+{
+Relation	pg_constraint;
+HeapTuple	conTup,
+retval = NULL;
+SysScanDesc scan;
+ScanKeyData key;
+
+pg_constraint = table_open(ConstraintRelationId, AccessShareLock);
+ScanKeyInit(&key,
+Anum_pg_constraint_contypid,
+BTEqualStrategyNumber, F_OIDEQ,
+ObjectIdGetDatum(typid));
+scan = systable_beginscan(pg_constraint, ConstraintRelidTypidNameIndexId,
+true, NULL, 1, &key);
+
+while (HeapTupleIsValid(conTup = systable_getnext(scan)))
+{
+Form_pg_constraint con = (Form_pg_constraint) GETSTRUCT(conTup);
+
+/*
+* We're looking for a NOTNULL constraint that's marked validated.
+*/
+if (con->contype != CONSTRAINT_NOTNULL)
+continue;
+if (!con->convalidated)
+continue;
+
+/* Found it */
+retval = heap_copytuple(conTup);
+break;
+}
+
+systable_endscan(scan);
+table_close(pg_constraint, AccessShareLock);
+
+return retval;
+}
+
 /*
 * Given a pg_constraint tuple for a not-null constraint, return the column
 * number it is for.