Horton

Assert failure on running a completed portal again

Yugo Nagata <nagata@sraoss.co.jp>

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From: Yugo Nagata <nagata@sraoss.co.jp>
To: pgsql-hackers@postgresql.org
Date: 2024-12-05T21:25:49Z
Lists: pgsql-hackers

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Hi,

I notice that the following Assert in PortalRun fails when a same portal is
executed more than once by an Execute message whose "max number of rows"
is specified to zero, that is, "no limit".  

        /* Set run_once flag.  Shouldn't be clear if previously set. */
        Assert(!portal->run_once || run_once);
        portal->run_once = run_once;

I tested this using pgproto [1] in Pgpool-II.

I believe the server should return CommanComplete normally in this case. 
his can be fixed by not setting execute_is_fetch flag (run_once as the result)
when the portal is already completed since no rows will be fetched in this case.
I've attached a pach in this approach.

[1] https://www.pgpool.net/docs/latest/en/html/pgproto.html

Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>

Commits

  1. Doc: add some commentary about ExecutorRun's NoMovement special case.

  2. Simplify executor's determination of whether to use parallelism.

  3. Allow for parallel execution whenever ExecutorRun() is done only once.