| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Performance improvement for joins where outer side is unique |
| Date: | 2016-04-01 16:52:42 |
| Message-ID: | 30364.1459529562@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
> On 12 March 2016 at 11:43, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> It seems like the major intellectual complexity here is to figure out
>> how to detect inner-side-unique at reasonable cost. I see that for
>> LEFT joins you're caching that in the SpecialJoinInfos, which is probably
>> fine. But for INNER joins it looks like you're just doing it over again
>> for every candidate join, and that seems mighty expensive.
> I have a rough idea for this, but I need to think of it a bit more to
> make sure it's bulletproof.
Where are we on this? I had left it alone for awhile because I supposed
that you were going to post a new patch, but it's been a couple weeks...
regards, tom lane
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