Re: Postgresql 7.0 JDBC exceptions - broken connections ?

Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> writes:

> I think that this and the "Tuple received before MetaData" issue could
> have a common cause, namely running out of memory on the client side
> and not recovering well. libpq is known to emit its equivalent of
> "Tuple received before MetaData" when the backend hasn't violated the
> protocol at all. What happens is that libpq runs out of memory while
> trying to accumulate a large query result, "recovers" by resetting
> itself to no-query-active state, and then is surprised when the next
> message is another tuple. (Obviously this error recovery plan needs
> work, but no one's got round to it yet.) I wonder whether the JDBC
> driver has a similar problem, and whether these queries could have
> been retrieving enough data to trigger it?
>

This could be a possible explanation, as some of the queries may indeed
retrieve large amounts of data. I have also noticed a couple of "Out of
Memory" exceptions that could be related(This seem to be "temporary" out of
memory exceptions, and not permanent memory leaks; so I guess these could
be caused by queries returning huge amounts of data).

> Another possibility is that the client app is failing to release
> query results when done with them, which would eventually lead to
> an out-of-memory condition even with not-so-large queries.

I don't think this is the case. I've been running the application through
OptimizeIT to profile memory and CPU usage and I haven't been able to spot
any memory leakages in the driver; The quality of the JDBC driver is
actually our main reason to migrate our application to PostgreSQL.

regards,

Gunnar