Re: Performance improvement for joins where outer side is unique

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: David Rowley <david(dot)rowley(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Performance improvement for joins where outer side is unique
Date: 2017-01-27 18:39:17
Message-ID: 2028.1485542357@sss.pgh.pa.us
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Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Jan 27, 2017 at 11:44 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> I'm afraid though that we may have to do something about the
>> irrelevant-joinquals issue in order for this to be of much real-world
>> use for inner joins.

> Maybe, but it's certainly not the case that all inner joins are highly
> selective. There are plenty of inner joins in real-world applications
> where the join product is 10% or 20% or 50% of the size of the larger
> input.

Um ... what's that got to do with the point at hand?

regards, tom lane

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