From: | "Scott Marlowe" <scott(dot)marlowe(at)gmail(dot)com> |
---|---|
To: | "Greg Smith" <gsmith(at)gregsmith(dot)com> |
Cc: | "Sam Mason" <sam(at)samason(dot)me(dot)uk>, pgsql-general(at)postgresql(dot)org |
Subject: | Re: WAL Log Size |
Date: | 2008-02-29 07:25:13 |
Message-ID: | dcc563d10802282325g53b5b614s5bbc9cecbf22d9f1@mail.gmail.com |
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Thread: | |
Lists: | pgsql-general |
On Fri, Feb 29, 2008 at 1:08 AM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:
> On Fri, 29 Feb 2008, Sam Mason wrote:
>
> > Just out of interest, why doesn't it do the following?
> >
> > BEGIN;
> > create table xlog_switch as
> > select '0123456789ABCDE' from generate_series(1,1000000);
> > ROLLBACK;
>
> I'm not 100% sure here what happens when you do the above, and it depends
> on version, but there are cases where creating a new or empty table in a
> transaction is optimized to not create any WAL as a performance
> improvement. This has become a common idiom for that reason:
That's why the create table statement up there had the from
generate_series bit...
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