cockroachdb crdb - enums not working with prepared statements

• asyncpg version: 0.21.0
• CockroachDB version: v20.2.1
• PostgreSQL version: 12.4
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?:
• Python version: 3.9.0
• Platform: linux-x86_64
• Do you use pgbouncer?: no
• Did you install asyncpg with pip?: yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and
  uvloop?: didn't test uvloop

enums have just been added to crdb. testing asyncpg shows an issue with prepared statements.

running this:

await conn.execute("INSERT INTO accounts2 (id, balance, mode) VALUES ($1, $2, $3)", 9, 2000, "active", )
throws

    statement = await self._protocol.prepare(stmt_name, query, timeout)
  File "asyncpg/protocol/protocol.pyx", line 163, in prepare
asyncpg.exceptions.FeatureNotSupportedError: CTEs may not be correlated

the prepared statement works fine in pgsql. enums work fine without prepared statements.

I have a silly bug exerciser, but needs some cleanup, you can see the relevant test2 functions if you need working code. i've tested psycopg2 and asyncpg against crdb and pgsql and out of the four runs, only asyncpg+crdb shows an issue.

crdbissues.py.txt

Bắt đầu với reproducer crdbissues.py.txt đính kèm và đường dẫn prepare được trích dẫn tại asyncpg/protocol/protocol.pyx:163. So sánh hành vi chèn enum đã prepare trên CockroachDB và PostgreSQL, sau đó lần theo việc xử lý protocol tương ứng. Hoàn thành khi một regression test bao quát prepared enum statement và chạy thành công trên cơ sở dữ liệu bị ảnh hưởng mà không có lỗi CTE.