| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Heikki Linnakangas <heikki(at)enterprisedb(dot)com> |
| Cc: | apoc9009(at)yahoo(dot)de, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [FEATURE REQUEST] Streaming Onlinebackup (Maybe OFFTOPIC) |
| Date: | 2007-09-06 20:25:27 |
| Message-ID: | 1189110327.9243.17.camel@dogma.ljc.laika.com |
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| Lists: | pgsql-hackers |
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.
Regards,
Jeff Davis
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