On Thu, 2007-09-06 at 12:08 +0100, Heikki Linnakangas wrote:
> With file-based log shipping, you can get down to 1 second, by using the
> archive_timeout setting. It will produce a lot of log files with very
> little content in them, but they will compress well.

I tried doing a couple pg_switch_xlog() in quick succession, and the WAL
files that represent less than a second of actual data don't seem much
more compressible than the rest.

I think WAL compression has been talked about before, with ideas such as
removing unneeded full page images. However, it seems like it would be
easy to get a lot of the benefit by just having a utility that could
discard useless contents that are left over from a previously-recycled
file, and then could just reconstruct it later with zeros.

        Jeff Davis

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