Fix pg_get_serial_sequence in SQL adapter (#7581)

edb/pgsql/resolver/static.py

@@ -220,6 +220,10 @@ def eval_FuncCall(
             span=expr.span,
         )
 
+    if fn_name == "pg_get_serial_sequence":
+        # we do not expose sequences, so any calls to this function returns NULL
+        return pgast.NullConstant()
+
     if fn_name == "to_regclass":
         arg = require_a_string_literal(expr, fn_name, ctx)
         return to_regclass(arg, ctx=ctx)
@@ -306,6 +310,8 @@ def cast_to_regclass(param: pgast.BaseExpr, ctx: Context) -> pgast.BaseExpr:
     """
 
     expr = eval(param, ctx=ctx)
+    if isinstance(expr, pgast.NullConstant):
+        return pgast.NullConstant()
     if isinstance(expr, pgast.StringConstant):
         return to_regclass(expr.val, ctx=ctx)
     if isinstance(expr, pgast.NumericConstant):

tests/test_sql_query.py

@@ -919,6 +919,23 @@ async def test_sql_query_static_eval_04(self):
         )
         self.assertEqual(res, [[11]])
 
+    async def test_sql_query_static_eval_05(self):
+        # pg_get_serial_sequence always returns NULL, we don't expose sequences
+
+        res = await self.squery_values(
+            '''
+            SELECT
+              CAST(
+                CAST(
+                  pg_catalog.pg_get_serial_sequence('a', 'b')
+                  AS REGCLASS
+                )
+                AS OID
+              )
+            '''
+        )
+        self.assertEqual(res, [[None]])
+
     async def test_sql_query_be_state(self):
         con = await self.connect(database=self.con.dbname)
         try: