Skip site navigation (1) Skip section navigation (2)

Re: Proposed patch to make mergejoin cost estimation more symmetric

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-patches(at)postgreSQL(dot)org
Subject: Re: Proposed patch to make mergejoin cost estimation more symmetric
Date: 2007-12-07 15:15:35
Message-ID: 19957.1197040535@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-patches
Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> writes:
> Yes, but how can you tell by looking at the explain?  I think the point
> is that the "fraction that would be skipped" should be reported somehow.

It is: it's directly reflected in the startup cost.  Previously, a
mergejoin would always have startup cost equal to the sum of its
input startup costs (hence, zero in the cases of interest here).

			regards, tom lane

In response to

pgsql-patches by date

Next:From: Tom LaneDate: 2007-12-07 15:37:45
Subject: Re: Problem with ControlFileData structure being ABI depe ndent
Previous:From: Simon RiggsDate: 2007-12-07 15:14:45
Subject: Re: Proposed patch to make mergejoin cost estimationmore symmetric

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group