Date: Tue, 29 Jun 2021 09:54:49 -0400
From: Alvaro Herrera <alvaro.herrera@2ndquadrant.com>
To: Boris Kolpackov <boris@codesynthesis.com>
Cc: pgsql-hackers@lists.postgresql.org
Subject: Re: Pipeline mode and PQpipelineSync()
Message-ID: <202106291354.wyn7ar6emdm6@alvherre.pgsql>
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On 2021-Jun-24, Boris Kolpackov wrote:

> I've hit another similar case except now an unexpected NULL result is
> returned in the middle of PGRES_PIPELINE_ABORTED result sequence. The
> call sequence is as follows:
> 
> PQsendQueryPrepared() # INSERT #1
> PQflush()
> PQsendQueryPrepared() # INSERT #2
> PQflush()
> ...
> PQsendQueryPrepared() # INSERT #251 -- insert duplicate PK
> PQflush()
> ...
> PQsendQueryPrepared() # INSERT #343
> PQflush()
> PQconsumeInput()      # At this point select() indicates we can read.
> PQgetResult()         # NULL -- unexpected but skipped (see prev. email)
> PQgetResult()         # INSERT #1
> PQgetResult()         # NULL
> PQgetResult()         # INSERT #2
> PQgetResult()         # NULL
> ...
> PQgetResult()         # INSERT #251 error result, SQLSTATE 23505
> PQgetResult()         # NULL
> PQgetResult()         # INSERT #252 PGRES_PIPELINE_ABORTED
> PQgetResult()         # NULL
> PQgetResult()         # INSERT #253 PGRES_PIPELINE_ABORTED
> PQgetResult()         # NULL
> ...
> PQgetResult()         # INSERT #343 NULL (???)
> 
> Notice that result #343 corresponds to the last PQsendQueryPrepared()
> call made before the socket became readable (it's not always 343 but
> around there).

No luck reproducing any problems with this sequence as yet.

-- 
Álvaro Herrera                            39°49'30"S 73°17'W