What Derby version is this? Do you have an index on groupCol?
On Mon, Feb 8, 2010 at 3:11 PM, Ronald Rudy <ronchal...@gmail.com> wrote: > I've gotten to the point where I seem to be able to frequently induce > OutOfMemoryErrors when executing a statement like this one: > > SELECT groupCol, count(*) FROM myTable GROUP BY groupCol; > > The total number of records doesn't seem terribly large (about 400,000 > records) though while I'm executing the above statement there are likely some > inserts and deletes happening concurrently. I don't need anything > transactional here, I'm really just monitoring a table from a separate > network connection. > > In our app the database runs in its own JSVC daemon as a NetworkServer with > 512MB allocated to it. Page cache size is set to 2000. Page size should > be Derby default (4096 I think). > > I cannot be 100% sure that the above is specifically what is causing the > error, but I can say that I haven't seen memory errors until I started > monitoring this table frequently and even then I really only saw it when the > table size started getting a bit bigger (not big by any stretch, but > 300k > rows). > > The table itself is not really big - there are 7 varchar columns along with > an ID column. > > In this production-level situation stability is more important than > performance. I'd like Derby configured so that no matter what is requested > SQL wise the daemon itself is not impacted. > > I'd also like to be able to build in some handling code perhaps that if/when > an OutOfMemoryError is encountered, it will automatically restart - for this > I might need to add a script with -XX:OnOutOfMemoryError as a JVM option > unless there's some way to handle this internally? > > -Ron
