Re: COUNT(*) and index-only scans - Mailing list pgsql-hackers

From Greg Stark
Subject Re: COUNT(*) and index-only scans
Date
Msg-id CAM-w4HO=zSNmyZcrtx9PYxyqxjObEgO+YcP_mRA4AUucZgh6hA@mail.gmail.com
Whole thread Raw
In response to Re: COUNT(*) and index-only scans  ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
List pgsql-hackers
On Wed, Oct 12, 2011 at 4:26 PM, Kevin Grittner
<Kevin.Grittner@wicourts.gov> wrote:
>> But it matters a *lot* when they heap pages are not in shared
>> buffers
>
> Yeah, obviously it matters more if you actually need to add a random
> disk read.

To be fair the indexes are also random I/O. So the case that really
matters is when the index fits in RAM but the heap does not.

-- 
greg


pgsql-hackers by date:

Previous
From: "Kevin Grittner"
Date:
Subject: Re: COUNT(*) and index-only scans
Next
From: Tom Lane
Date:
Subject: Re: COUNT(*) and index-only scans