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

添付された crdbissues.py.txt の再現プログラムと、asyncpg/protocol/protocol.pyx:163 で引用されている prepare パスから始めます。CockroachDB と PostgreSQL における prepared enum insert の動作を比較し、その結果生じるプロトコル処理を追跡します。prepared enum statement をカバーする回帰テストがあり、対象のデータベースに対して CTE エラーなしで成功すれば完了です。