Don't change asyncpg's "char" codec

This codec was used to ensure the "pg_attribute.generated"
column comes back as a string and not bytes, matching how
other PG drivers treat this datatype.   However, this breaks
asyncpg's internal implementation of set_type_codec going forward
and the "char" datatype is actually a bytes in any case.
So at the moment it appears psycopg2/pg8000 are broken for mis-treatment
of the datatype and asyncpg is broken in that it was allowing
us to change a codec that it appears to rely upon internally.

Fixes: #5586
Change-Id: I937eba315904721aa4e2726b95432910a8affe5f

1 files changed, 4 insertions, 19 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/asyncpg.py b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
index 780e23844..6fa1dd78b 100644
--- a/lib/sqlalchemy/dialects/postgresql/asyncpg.py
+++ b/lib/sqlalchemy/dialects/postgresql/asyncpg.py
@@ -486,28 +486,13 @@ class AsyncAdapt_asyncpg_connection:
     async def _setup_type_codecs(self):
         """set up type decoders at the asyncpg level.
 
-        this is first to accommodate the "char" value of
-        pg_catalog.pg_attribute.attgenerated being returned as bytes.
-        Even though the doc at
-        https://magicstack.github.io/asyncpg/current/usage.html#type-conversion
-        claims "char" is returned as "str", it looks like this is actually
-        the 'bpchar' datatype, blank padded.  'char' seems to be some
-        more obscure type (oid 18) and asyncpg codes this to bytea:
-        https://github.com/MagicStack/asyncpg/blob/master/asyncpg/protocol/
-        codecs/pgproto.pyx#L26
-
-        all the other drivers treat this as a string.
+        these are set_type_codec() calls to normalize
+        There was a tentative decoder for the "char" datatype here
+        to have it return strings however this type is actually a binary
+        type that other drivers are likely mis-interpreting.
 
         """
 
-        await self._connection.set_type_codec(
-            "char",
-            schema="pg_catalog",
-            encoder=lambda value: value,
-            decoder=lambda value: value,
-            format="text",
-        )
-
     def _handle_exception(self, error):
         if not isinstance(error, AsyncAdapt_asyncpg_dbapi.Error):
             exception_mapping = self.dbapi._asyncpg_error_translate