Horton

Re: Asynchronous Append on postgres_fdw nodes.

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: etsuro.fujita@gmail.com
Cc: pryzby@telsasoft.com, a.lepikhov@postgrespro.ru, movead.li@highgo.ca, pgsql-hackers@lists.postgresql.org
Date: 2020-11-20T11:26:47Z
Lists: pgsql-hackers 
At Fri, 20 Nov 2020 20:16:42 +0900 (JST), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in 
me> +		/* If this was the second part of an async request, we must fetch until NULL. */
me> +		if (fsstate->async_aware)
me> +		{
me> +			/* call once and raise error if not NULL as expected? */
me> +			while (PQgetResult(conn) != NULL)
me> +				;
me> +			fsstate->conn_state->async_query_sent = false;
me> +		}
me> 
me> PQgetResult() receives the result of a query at once. This code means
me> several queries (FETCHes) are queued in, and we discard the result
me> except the last one.  Actually the res is just PQclear'd just after so
me> this just discards *all* result of maybe more than one FETCHes.  I
me> think something's wrong if we need this.

I was wrong, it is worse. That leaks the returned PGresult.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Improve comments for trivial_subqueryscan().

  2. Disable asynchronous execution if using gating Result nodes.

  3. Allow asynchronous execution in more cases.

  4. Doc: Further update documentation for asynchronous execution.

  5. Fix rescanning of async-aware Append nodes.

  6. Doc: Update documentation for asynchronous execution.

  7. Fix EXPLAIN ANALYZE for async-capable nodes.

  8. Minor code cleanup in asynchronous execution support.

  9. Adjust input value to WaitEventSetWait() in ExecAppendAsyncEventWait().

  10. Add support for asynchronous execution.