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Re: Proposed patch: synchronized_scanning GUC variable

From: Gregory Stark <stark(at)enterprisedb(dot)com>
To: "Kris Jurka" <books(at)ejurka(dot)com>
Cc: "Jeff Davis" <pgsql(at)j-davis(dot)com>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <pgsql-patches(at)postgreSQL(dot)org>
Subject: Re: Proposed patch: synchronized_scanning GUC variable
Date: 2008-01-29 11:04:48
Message-ID: 87myqovqnj.fsf@oxford.xeocode.com (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
"Kris Jurka" <books(at)ejurka(dot)com> writes:

> On Mon, 28 Jan 2008, Jeff Davis wrote:
>
>> I think that pg_dump is a reasonable use case for synchoronized scans
>> when the table has not been clustered. It could potentially make pg_dump
>> have much less of a performance impact when run against an active
>> system.
>
> One of the advantages I see with maintaining table dump order is that rsyncing
> backups to remote locations will work better.

I can't see what scenario you're talking about here. pg_dump your live
database, restore it elsewhere, then shut down the production database and run
rsync from the live database to the restored one? Why not just run rsync for
the initial transfer?

I can't see that working well for a real database and a database loaded from a
pg_dump anyways. Every dead record will introduce skew, plus page headers, and
every record will have a different system data such as xmin for one.

-- 
  Gregory Stark
  EnterpriseDB          http://www.enterprisedb.com
  Get trained by Bruce Momjian - ask me about EnterpriseDB's PostgreSQL training!

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