Maciek Sakrejda <m.sakrejda@xxxxxxxxx> writes: > We've run into a perplexing issue with a customer database. He moved > from a 9.1.5 to a 9.1.6 and upgraded from an EC2 m1.medium (3.75GB > RAM, 1.3 GB shmmax), to an m2.xlarge (17GB RAM, 5.7 GB shmmax), and is > now regularly getting constant errors regarding running out of shared > memory (there were none on the old system in the recent couple of > days' logs from before the upgrade): > ERROR: out of shared memory > HINT: You might need to increase max_pred_locks_per_transaction. This has nothing to do with work_mem nor maintenance_work_mem; rather, it means you're running out of space in the database-wide lock table. You need to take the hint's advice. > The query causing this has structurally identical plans on both systems: > old: http://explain.depesz.com/s/Epzq > new: http://explain.depesz.com/s/WZo The query in itself doesn't seem very exceptional. I wonder whether you recently switched your application to use serializable mode? But anyway, a query's demand for predicate locks can depend on a lot of not-very-visible factors, such as how many physical pages the tuples it accesses are spread across. I don't find it too hard to credit that yesterday you were just under the limit and today you're just over even though "nothing changed". regards, tom lane -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
