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?

Bắt đầu bằng cách đọc asyncpg/protocol/protocol.pyx quanh dòng 664, sau đó lần theo ngữ cảnh pool.acquire và các lệnh gọi tuần tự fetchrow, fetchval và fetch được mô tả trong báo cáo. Hãy thử thu gọn hành vi thành một ví dụ có thể tái hiện bằng asyncio và uvloop. Công việc được xem là hoàn tất khi xác định được thao tác xung đột hoặc ghi lại các chi tiết tái hiện còn thiếu cần thiết để chẩn đoán vấn đề.