
> In the brave new world of WAL, Postgres does not flush dirty buffers
to
> disk at transaction commit, relying on WAL to clean up if a database
or
> system failure occurs.  If we don't log page images to WAL then I
think
> there's a hole here wherein a Postgres crash can lose data even though
> no failure of the surrounding OS occurs.  Maybe it's safe, but I'm not
> convinced.

It should be (imho *is*) safe for heap pages, but not for index pages.
The reasoning for heap pages is, that the WAL code (pre page image)
already
coped with future heap page versions.

I would not expect it to work for index pages, since one "feature" of
the page images was to "undo" future index operations.

Andreas

Tue, 27 Nov 2001 11:04:42 +0100
"Zeugswetter Andreas SB SD" <ZeugswetterA@spardat.at>
Re: Pre-page images in WAL 