Avoid performing type introspection on known types (#1243)

Type codec setup functions will no longer attempt to introspect the type
if it's one of the known builtin types.

Fixes: #1206
Fixes: #1138
Fixes: #1242

Author: elprans

asyncpg/connection.py

@@ -534,26 +534,18 @@ async def _introspect_types(self, typeoids, timeout):
         return result
 
     async def _introspect_type(self, typename, schema):
-        if (
-            schema == 'pg_catalog'
-            and typename.lower() in protocol.BUILTIN_TYPE_NAME_MAP
-        ):
-            typeoid = protocol.BUILTIN_TYPE_NAME_MAP[typename.lower()]
-            rows = await self._execute(
-                introspection.TYPE_BY_OID,
-                [typeoid],
-                limit=0,
-                timeout=None,
-                ignore_custom_codec=True,
-            )
-        else:
-            rows = await self._execute(
-                introspection.TYPE_BY_NAME,
-                [typename, schema],
-                limit=1,
-                timeout=None,
-                ignore_custom_codec=True,
-            )
+        if schema == 'pg_catalog' and not typename.endswith("[]"):
+            typeoid = protocol.BUILTIN_TYPE_NAME_MAP.get(typename.lower())
+            if typeoid is not None:
+                return introspection.TypeRecord((typeoid, None, b"b"))
+
+        rows = await self._execute(
+            introspection.TYPE_BY_NAME,
+            [typename, schema],
+            limit=1,
+            timeout=None,
+            ignore_custom_codec=True,
+        )
 
         if not rows:
             raise ValueError(

asyncpg/introspection.py

@@ -7,10 +7,12 @@
 from __future__ import annotations
 
 import typing
+from .protocol.protocol import _create_record  # type: ignore
 
 if typing.TYPE_CHECKING:
     from . import protocol
 
+
 _TYPEINFO_13: typing.Final = '''\
     (
         SELECT
@@ -267,16 +269,12 @@
 '''
 
 
-TYPE_BY_OID = '''\
-SELECT
-    t.oid,
-    t.typelem     AS elemtype,
-    t.typtype     AS kind
-FROM
-    pg_catalog.pg_type AS t
-WHERE
-    t.oid = $1
-'''
+def TypeRecord(
+    rec: typing.Tuple[int, typing.Optional[int], bytes],
+) -> protocol.Record:
+    assert len(rec) == 3
+    return _create_record(  # type: ignore
+        {"oid": 0, "elemtype": 1, "kind": 2}, rec)
 
 
 # 'b' for a base type, 'd' for a domain, 'e' for enum.