| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | James Coleman <jtc331(at)gmail(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Rafia Sabih <rafia(dot)pghackers(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Shaun Thomas <shaun(dot)thomas(at)2ndquadrant(dot)com>, Dmitry Dolgov <9erthalion6(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, PostgreSQL Developers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Subject: | Re: [PATCH] Incremental sort (was: PoC: Partial sort) |
| Date: | 2020-03-13 17:36:44 |
| Message-ID: | 32110.1584121004@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
James Coleman <jtc331(at)gmail(dot)com> writes:
> On Tue, Mar 10, 2020 at 10:44 PM Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com> wrote:
>> 1) I see a bunch of failures in the regression test, due to minor
>> differences in the explain output. All the differences are about minor
>> changes in memory usage, like this:
>>
>> - "Sort Space Used": 30, +
>> + "Sort Space Used": 29, +
>>
>> I'm not sure if it happens on my machine only, but maybe the test is not
>> entirely stable.
> make check passes on multiple machines for me; what arch/distro are you using?
I think there's exactly zero chance of such output being stable across
different platforms, particularly 32-vs-64-bit. You'll need to either
drop that test or find some way to mask the variability.
> Is there a better way to test these? I would prefer these code paths
> have test coverage, but the standard SQL tests don't leave a good way
> to handle stuff like this.
In some places we use plpgsql code to filter the EXPLAIN output.
regards, tom lane
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