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

Re: So, is COUNT(*) fast now?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Robert Haas <robertmhaas(at)gmail(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: So, is COUNT(*) fast now?
Date: 2011-10-21 18:33:31
Message-ID: 29572.1319222011@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> On Fri, Oct 21, 2011 at 2:08 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> What this test case proves is that btree's overhead per index
>> tuple touched is significantly more than the cost of the fastest path
>> through HeapTupleSatisfiesMVCC, which I don't find surprising
>> considering how much sweat has been expended on that code path over the
>> years.

> I think HeapTupleSatisfiesMVCC is probably being skipped anyway in
> this case, since all the heap pages should be PD_ALL_VISIBLE.

Proves my point ;-) ... you're comparing a code path that's been beat on
for *years* with one that just got written.

			regards, tom lane

In response to

Responses

pgsql-hackers by date

Next:From: Pavel StehuleDate: 2011-10-21 18:44:27
Subject: Re: psql command for bytea output
Previous:From: Tom LaneDate: 2011-10-21 18:30:17
Subject: Re: Synchronized snapshots versus multiple databases

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