BUG #8728: Toast table much larger on replica

The following bug has been logged on the website:

Bug reference: 8728
Logged by: Maciek Sakrejda
Email address: m(dot)sakrejda(at)gmail(dot)com
PostgreSQL version: 9.2.6
Operating system: Ubuntu 12.04 LTS 64-bit
Description:

I noticed that one of a customer's toast tables is much larger on a replica
than it is on the primary. Basically "ls base/16385/16650* | wc -l" gives me
29 on the old DB, 38 on the replica. The table in question is a toast table,
`pg_toast_16647`.

The somewhat strange thing is that according to our monitoring (via
`pg_database_size`), the replica was *always* 10GB bigger, right off the
bat, and the primary was never that big. The replica was set up with WAL-E.

The primary is 9.2.5; the replica is 9.2.6. The replica has since stopped
replicating the primary, but I don't think that's relevant here--the size
discrepancy predates this.

Any ideas?