Re: Decreasing WAL size effects - Mailing list pgsql-general

From Kyle Cordes
Subject Re: Decreasing WAL size effects
Date
Msg-id 490A1C53.7040602@kylecordes.com
Whole thread Raw
In response to Re: Decreasing WAL size effects  (Greg Smith <gsmith@gregsmith.com>)
Responses Re: Decreasing WAL size effects  (Jason Long <mailing.list@supernovasoftware.com>)
Re: Decreasing WAL size effects  (Greg Smith <gsmith@gregsmith.com>)
List pgsql-general
Greg Smith wrote:

> there's no chance it can accidentally look like a valid segment.  But
> when an existing segment is recycled, it gets a new header and that's
> it--the rest of the 16MB is still left behind from whatever was in that
> segment before.  That means that even if you only write, say, 1MB of new

[...]

> What clearxlogtail does is look inside the WAL segment, and it clears
> the "tail" behind the portion of that is really used.  So our example
> file would end up with just the 1MB of useful data, followed by 15MB of


It sure would be nice if there was a way for PG itself to zero the
unused portion of logs as they are completed, perhaps this will make it
in as part of the ideas discussed on this list a while back to make a
more "out of the box" log-ship mechanism?


--
Kyle Cordes
http://kylecordes.com

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