Horton

Re: Lock problem with autovacuum truncating heap

Itagaki Takahiro <itagaki.takahiro@gmail.com>

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From: Itagaki Takahiro <itagaki.takahiro@gmail.com>
To: Simon Riggs <simon@2ndquadrant.com>
Cc: Jan Wieck <JanWieck@yahoo.com>, PostgreSQL Development <pgsql-hackers@postgresql.org>
Date: 2011-03-26T17:44:09Z
Lists: pgsql-hackers 
On Sun, Mar 27, 2011 at 01:12, Simon Riggs <simon@2ndquadrant.com> wrote:
>> At the same time I would
>> change count_nondeletable_pages() so that it uses a forward scan direction
>> (if that leads to a speedup).

+1.

> Do we need that? Linux readahead works in both directions doesn't it?
> Guess it wouldn't hurt too much.

Yes, probably. AFAIK, RHEL 5 cannot readahead in backward scans.
It might be improved in the latest kernel, but it would be safe
not to rely on kernels except simple forward scans.

-- 
Itagaki Takahiro