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

Re: min/max planner optimization

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: "PostgreSQL-development Hackers" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: min/max planner optimization
Date: 2007-10-27 15:00:26
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> The only case where the optimization is a win is where you have a
> zero-startup-cost subplan, and the only way to get sorted output with zero
> startup cost is an indexscan.

Sure but there could be other nodes above the index scan which preserve the
order. In particular nested loop and merge joins. Unique also preserves the
order but I can't see how it could be useful here. And of course potentially
Append nodes in the future...

  Gregory Stark

In response to


pgsql-hackers by date

Next:From: Tom LaneDate: 2007-10-27 15:04:19
Subject: Re: Datum should be defined outside postgres.h
Previous:From: Pavel StehuleDate: 2007-10-27 14:45:47
Subject: Re: Proposal: real procedures again (8.4)

Privacy Policy | About PostgreSQL
Copyright © 1996-2017 The PostgreSQL Global Development Group