Re: Very bizarre bug with corrupted index

Tom,

> Did you shut down the postmaster (or at least force a checkpoint)
> before examining the busted index?  It's barely possible that the zeroes
> on disk didn't correspond to what was in buffer cache.  How big was this
> index, anyway?

The index is pretty small, actually, (< 20 indexed rows in the table) altho=
ugh=20
it does suffer severe attenuation between VACUUMS due to numerous updates (=
up=20
to 100,000 discarded rows in some periods btw. 5min. VACUUM.)

However, I did find out that they did *not* shut down Postmaster before=20
copying the file.   So the contents are not reliable.   Unfortunately, the=
=20
original installation is long gone, so we'll have to wait until it happens=
=20
again (or, more likely, not) to analyze.=20=20=20

Fortunately or not, it may not happen again; they're running this version o=
f=20
the database on 3-5 overloaded test systems for the last month+ and this is=
=20
the first such error.

> But I'm inclined to blame the filesystem --- I can't think of any
> plausible mechanism in Postgres that would zero out all of a file.
> What filesystem are you using?

Ext3, as it turns out.

--=20
Josh Berkus
Aglio Database Solutions
San Francisco