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

Re: [PATCHES] Proposed patch: synchronized_scanning GUCvariable

From: "Zeugswetter Andreas ADI SD" <Andreas(dot)Zeugswetter(at)s-itsolutions(dot)at>
To: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>,"Simon Riggs" <simon(at)2ndquadrant(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Neil Conway" <neilc(at)samurai(dot)com>,"Gregory Stark" <stark(at)enterprisedb(dot)com>,"Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>,<pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: [PATCHES] Proposed patch: synchronized_scanning GUCvariable
Date: 2008-01-29 09:40:40
Message-ID: E1539E0ED7043848906A8FF995BDA57902C23E73@m0143.s-mxs.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
> It's a good point that we don't want pg_dump to screw up the cluster 
> order, but that's the only use case I've seen this far for disabling 
> sync scans. Even that wouldn't matter much if our estimate for 
> "clusteredness" didn't get screwed up by a table that looks 
> like this: 
> "5 6 7 8 9 1 2 3 4"

I do think the guc to turn it off is useful, only I don't understand the
reasoning that pg_dump needs it to maintain the basic clustered
property.

Sorry, but I don't grok this at all.
Why the heck would we care if we have 2 parts of the table perfectly
clustered,
because we started in the middle ? Surely our stats collector should
recognize
such a table as perfectly clustered. Does it not ? We are talking about
one
breakage in the readahead logic here, this should only bring the
clustered property
from 100% to some 99.99% depending on table size vs readahead window.

Andreas

In response to

Responses

pgsql-hackers by date

Next:From: Gregory StarkDate: 2008-01-29 10:55:38
Subject: Re: [PATCHES] Proposed patch: synchronized_scanning GUCvariable
Previous:From: Premsun CholtanwanichDate: 2008-01-29 09:27:47
Subject: How to use VB6 for store image to postgresql?

pgsql-patches by date

Next:From: Gregory StarkDate: 2008-01-29 10:55:38
Subject: Re: [PATCHES] Proposed patch: synchronized_scanning GUCvariable
Previous:From: Heikki LinnakangasDate: 2008-01-29 08:20:41
Subject: Re: [PATCHES] Proposed patch: synchronized_scanningGUCvariable

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