Horton

Re: Pipeline mode and PQpipelineSync()

Boris Kolpackov <boris@codesynthesis.com>

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From: Boris Kolpackov <boris@codesynthesis.com>
To: Alvaro Herrera <alvaro.herrera@2ndquadrant.com>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2021-06-24T09:06:42Z
Lists: pgsql-hackers 
Alvaro Herrera <alvaro.herrera@2ndquadrant.com> writes:

> Curious -- I just noticed that the server understands a message 'H' that
> requests a flush of the server buffer.  However, libpq has no way to
> generate that message as far as I can see.  I think you could use that
> to request results from the pipeline, without the sync point.
> 
> I wonder if it's worth adding an entry point to libpq to allow access to
> this.  

Yes, I think this can be useful. For example, an application may wish
to receive the result as soon as possible in case it's used as input
to some further computation.


> PQrequestFlush() or something like that ...

I think I would prefer PQflushResult() or something along these
lines ("request" is easy to misinterpret as "client request").

Commits

  1. libpq: Fix sending queries in pipeline aborted state

  2. Fix libpq state machine in pipeline mode

  3. Add PQsendFlushRequest to libpq