Re: Instability in partition_prune test?

On 13 April 2018 at 10:29, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> https://buildfarm.postgresql.org/cgi-bin/show_log.pl?nm=elver&dt=2018-04-12%2018%3A18%3A05
>
> partition_prune ... FAILED
>
> Subplans Removed: 6
> -> Parallel Seq Scan on ab_a2_b1 (actual rows=0 loops=1)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
> ! -> Parallel Seq Scan on ab_a2_b2 (actual rows=0 loops=1)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
> -> Parallel Seq Scan on ab_a2_b3 (actual rows=0 loops=1)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
> --- 1608,1614 ----
> Subplans Removed: 6
> -> Parallel Seq Scan on ab_a2_b1 (actual rows=0 loops=1)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
> ! -> Parallel Seq Scan on ab_a2_b2 (actual rows=0 loops=2)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
> -> Parallel Seq Scan on ab_a2_b3 (actual rows=0 loops=1)
> Filter: ((a >= $1) AND (a <= $2) AND (b < 4))
>
> This is a Parallel Append with three processes working on three
> subplans. It looks like one of the subplans got executed twice?

Hi Thomas,

Thanks for the report. If you're able to run the scripts in [1] and
confirm you can reproduce the failure, if so, then revert the code
back to 5c0675215 and see if you still get the additional loop.

You'll need to update the expected results once back in 5c0675215 as
the 6 subplans will no longer be removed.

I've been unable to reproduce this so keen to get results from a
machine that can.

[1] https://www.postgresql.org/message-id/CAKJS1f8o2Yd%3DrOP%3DEt3A0FWgF%2BgSAOkFSU6eNhnGzTPV7nN8sQ%40mail.gmail.com

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