BUG #5675: out of memory at request size 32Mb

The following bug has been logged online:

Bug reference: 5675
Logged by: Andreas Pflug
Email address: pgadmin(at)pse-consulting(dot)de
PostgreSQL version: 8.4.4
Operating system: Linux 2.6.26 i686
Description: out of memory at request size 32Mb
Details:

A slony 2.0 cluster running for a year, no config changes lately. Slony has
to replicate a table with a bytea column; maximum so far was a little over
32MB.

Lately, the slave's slon process fails to replicate. The server reports "out
of memory", "Failed on request of size 33554432.". The slon log shows an
insert was the failing statement, the server log spits out its memory
contexts but not the failing statement.

One log line that catched my attention was
MessageContext: 485902696 total in 6 blocks; 32160 free (16 chunks);
485870536 used
which is well beyond the configured memory limits (280MB shared_buffers,
temp 32MB, workmem 64MB)