Re: BUG #15250: ERROR: could not find pathkey item to sort

=?utf-8?q?PG_Bug_reporting_form?= <noreply(at)postgresql(dot)org> writes:
> I have complex queries in large tables that use memory for sorting items, we
> upgrate PostgreSQL from 9.1 to 9.4 and in this version we get this error:
> 'could not find pathkey item to sort'

That's a fairly common visible symptom for erroneous construction of a
plan inside the planner. It has nothing directly to do with memory
consumption, although it's possible that changing work_mem would encourage
the planner to choose a different plan shape that avoids the bug.

Another likely explanation for the problem appearing and disappearing is
that it could be sensitive to the current statistics for the table(s)
the query is on, in which case a background auto-analyze might be enough
to flip you from the plan shape with the problem to the plan shape
without.

Anyway, we'd certainly be interested to fix the problem if you can provide
a self-contained, reproducible test case. I'd suggest trying to generate
some dummy data that the query fails on.

regards, tom lane