Re: Using PQexecQuery in pipeline mode produces unexpected Close messages

At Thu, 16 Jun 2022 10:34:22 +0900 (JST), Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> wrote in
> PQgetResult() resets the state to IDLE while in pipeline mode.
>
> fe-exec.c:2171
>
> > if (conn->pipelineStatus != PQ_PIPELINE_OFF)
> > {
> > /*
> > * We're about to send the results of the current query. Set
> > * us idle now, and ...
> > */
> > conn->asyncStatus = PGASYNC_IDLE;
>
> And actually that code let the connection state enter to IDLE before
> CloseComplete. In the test case I posted, the following happens.
>
> PQsendQuery(conn, "SELECT 1;");
> PQsendFlushRequest(conn);
> PQgetResult(conn); // state enters IDLE, reads down to <CommandComplete>
> PQgetResult(conn); // reads <CloseComplete comes>
> PQpipelineSync(conn); // sync too late
>
> Pipeline feature seems intending to allow PQgetResult called before
> PQpipelineSync. And also seems allowing to call QPpipelineSync() after
> PQgetResult().
>
> I haven't come up with a valid *fix* of this flow..

The attached is a crude patch to separate the state for PIPELINE-IDLE
from PGASYNC_IDLE. I haven't found a better way..

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center