From: | Grzegorz Jaskiewicz <gj(at)pointblue(dot)com(dot)pl> |
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To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, "Gregory Stark" <stark(at)enterprisedb(dot)com>, "PostgreSQL-development Hackers" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: possible bug in 8.4 |
Date: | 2008-12-19 14:51:25 |
Message-ID: | 77D255AA-8E66-4D2E-AEDF-664FC36F7FC6@pointblue.com.pl |
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Lists: | pgsql-hackers |
On 2008-12-19, at 13:07, Tom Lane wrote:
> Grzegorz Jaskiewicz <gj(at)pointblue(dot)com(dot)pl> writes:
>> Filter: (NOT (hashed subplan))
> ^^^^^^^^^^^^^^
>
> If 8.3 does that, and 8.4 doesn't, it's most likely because you are
> using different work_mem settings.
you're right, as always :)
My point is, why is planner choosing plan on 8.4 that's obviously more
expensive ? even without sort_mem (work_mem) set to higher value ?
Obviously the plan is quite expensive, so probably sorting it on disc
- would be still cheaper.
The example is quite unrealistic, but I am trying different simple
things to test planner differences between these two versions, and see
if there's any improvement/regression.
This time I will set both work_mem to same value :)
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