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. 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 settings ( "select name, setting from pg_settings where source <> 'default' and name not like 'log%' and name not like 'ssl%' and name not like 'syslog%'" ) are almost identical (max_pred_locks_per_transaction itself is at the default): 17c17 < effective_cache_size | 1530000 --- > effective_cache_size | 337500 38c38 < shared_buffers | 424960 --- > shared_buffers | 93696 The kernels are both 2.6.32. The workload has not changed significantly. Could something in 9.1.6 be to blame here? Looking at the changelog, this seems vanishingly unlikely. Any ideas? -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
