Trying to debug `asyncpg.exceptions._base.InterfaceError: cannot perform operation: another operation is in progress`

• asyncpg version: 0.20.1
• PostgreSQL version: 12
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: no
• Python version: 3.7.5
• Platform: OS X
• 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?: yes

Hi!

I'm trying to debug an issue that I have with errors like asyncpg.exceptions._base.InterfaceError: cannot perform operation: another operation is in progress from this line: https://github.com/MagicStack/asyncpg/blob/dcef29804095990f25178b642b920f3fbcb4ca22/asyncpg/protocol/protocol.pyx#L664

I am trying to understand where I could have gone wrong. So, I would like to ask the following preliminary question:

Suppose my code interacts with asyncpg only through a pool, and only using context managers:

async with pool.acquire() as connection:
     ...

I also do not share the connection object around. On it, I use the methods fetchrow, fetchval and fetch. They are used sequentially from the same asyncio "thread" (for lack of better word). That is to say, they are never called in parallel.

In this setup, I would think that the error cannot perform operation: another operation is in progress never shows up, but it does. Am I missing something?

まず asyncpg/protocol/protocol.pyx の 664 行付近を読み、次に、報告で説明されている pool.acquire コンテキストと、fetchrow、fetchval、fetch の順次呼び出しを追ってください。asyncio と uvloop を使って、その挙動を再現可能な例に絞り込んでみてください。競合している操作を特定するか、診断に必要な不足している再現情報を文書化できれば完了です。