Re: Decreasing WAL size effects

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