| From: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Josh Berkus <josh(at)agliodbs(dot)com>, pgsql-hackers(at)postgresql(dot)org, Mark Wong <markwkm(at)gmail(dot)com> |
| Subject: | Re: nested loop semijoin estimates |
| Date: | 2015-06-02 19:44:15 |
| Message-ID: | 556E078F.2040502@2ndquadrant.com |
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| Lists: | pgsql-hackers |
On 06/02/15 21:39, Tom Lane wrote:
> I wrote:
>> I'm a bit disturbed by that, because AFAICS from the plans, these queries
>> did not involve any semi or anti joins, which should mean that the patch
>> would not have changed the planner's behavior.
>
> After contemplating my navel for awhile, it occurred to me that maybe the
> patch's changes in add_path_precheck could have caused behavioral changes
> at the margins. Could you try a run without that (without the last two
> hunks in pathnode.c)?
Yes, I think that's the cause. See the end of the message I sent just
before you posted this.
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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