Re: Performance improvement for joins where outer side is unique

From: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance improvement for joins where outer side is unique
Date: 2015-12-16 00:27:41
Message-ID: CAKJS1f_4hm3qwKeHYKftd+BQuYBgdNR+rk+XP_JW9EY-ALHZbQ@mail.gmail.com
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On 25 August 2015 at 17:25, David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>
wrote:

> On 24 August 2015 at 14:29, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>> David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> writes:
>> > I have to admit I don't much like it either, originally I had this as an
>> > extra property that was only seen in EXPLAIN VERBOSE.
>>
>> Seems like a reasonable design from here.
>
>
> The attached patch has the format in this way.
>

I've attached a rebased patch against current master as there were some
conflicts from the recent changes to LATERAL join.

On reviewing the patch again I was reminded that the bulk of the changes in
the patch are in analyzejoins.c. These are mostly just a refactor of the
current code to make it more reusable. The diff looks a bit more scary than
it actually is.

--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services

Attachment Content-Type Size
unique_joins_16-12-2015_7a290ab1.patch application/octet-stream 75.3 KB

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