BUG #7648: Momentary index corruption while in hot standby

The following bug has been logged on the website:

Bug reference:      7648
Logged by:          Daniel Farina
Email address:      daniel@heroku.com
PostgreSQL version: 9.0.9
Operating system:   Ubuntu 10.04
Description:        =


At more or less one point in time exactly (the same second, at minimum), a
couple of errors were raised on a hot standby while performing query access
that would nominally suggest corruption were raised:

PGError: ERROR: could not read block 556642 in file "base/16385/2904143.4":
read only 0 of 8192 =


Immediately thereafter, no occurrences of the error resurfaced and any
attempts to reproduce the issue with an identical query were met with
failure.

On investigation, this relfile is a fairly common beast: an integer btree
index being used for row identification (e.g. serial).

This is reading from a 9.0.8 Postgres.