I wrote:
> Hm. The stack trace is definitive that it's finding the bad data in a
> tuple that it's trying to print to the client, not in an index.
BTW, after a bit more reflection it occurs to me that it's not so much
that the data is necessarily *bad*, as that it seemingly doesn't match
the tuple descriptor that the backend's trying to interpret it with.
(In particular, the reported symptom would be consistent with finding
a small integer constant at a place where the descriptor expects to find
a variable-length field.) So that opens up a different line of thought
about how those could get out of sync on a standby. Are you in the
habit of issuing ALTER TABLE commands to add/delete/change columns on
these tables? In fact, is there any DDL whatsoever going on around the
time these failures happen?
regards, tom lane