Hi all, for further investigation we seperated the sub-SELECT from the DELETE statement and it looks like the SELECT is usually finished in some 100 milliseconds but after some minutes it suddenly takes some minutes. Peter 2006/10/20, Peter Bauer <peter.m.bauer@xxxxxxxxx>:
Hi all, we have a theory for the root of all evil which causes a reproducable deadlock which is not detected by Postgre: The DELETE statement contains a select which waits for a sharelock (according to pg_locks and pg_stat_activity) on rows locked by the UPDATE statement. The UPDATE itself waits to get a lock for some rows which are exclusively locked by the DELETE statement (got from its sub-SELECT). What do you think about this theory? thx, Peter 2006/10/19, Peter Bauer <peter.m.bauer@xxxxxxxxx>: > thank you very much, we will test it > > br, > Peter > > 2006/10/19, Jim C. Nasby <jim@xxxxxxxxx>: > > On Thu, Oct 19, 2006 at 01:57:56PM +0200, Peter Bauer wrote: > > In the update statement, don't wrap the ID values in quotes. At best > > it's extra work; at worse it will fool the planner into not using the > > index. > > > > > shared_buffers = 1000 # min 16 or max_connections*2, 8KB each > > > > This is *way* too small for what you're trying to do. Try a minimum of > > 10% of memory, and 50% of memory may be a better idea. > > > > > #temp_buffers = 1000 # min 100, 8KB each > > > #max_prepared_transactions = 5 # can be 0 or more > > > # note: increasing max_prepared_transactions costs ~600 bytes of shared memory > > > # per transaction slot, plus lock space (see max_locks_per_transaction). > > > work_mem = 20480 # min 64, size in KB, > > > > Making that active might help a lot, but beware of running the machine > > out of memory... > > > > > #max_fsm_pages = 20000 # min max_fsm_relations*16, 6 bytes each > > > > Probably needs to get increased. > > > > > #bgwriter_delay = 200 # 10-10000 milliseconds between rounds > > > #bgwriter_lru_percent = 1.0 # 0-100% of LRU buffers scanned/round > > > #bgwriter_lru_maxpages = 5 # 0-1000 buffers max written/round > > > #bgwriter_all_percent = 0.333 # 0-100% of all buffers scanned/round > > > #bgwriter_all_maxpages = 5 # 0-1000 buffers max written/round > > > > The background writer might need to be tuned more aggressively. > > > > > #checkpoint_warning = 30 # in seconds, 0 is off > > > > I'd set that closer to 300 to make sure you're not checkpointing a lot, > > though keep in mind that will impact failover time. > > > > > effective_cache_size = 44800 # typically 8KB each > > > > The machine only has 1/2G of memory? > > > > > #autovacuum_naptime = 60 # time between autovacuum runs, in secs > > > > I'd drop that to 30. > > > > > #autovacuum_vacuum_threshold = 1000 # min # of tuple updates before > > > # vacuum > > > #autovacuum_analyze_threshold = 500 # min # of tuple updates before > > > # analyze > > > #autovacuum_vacuum_scale_factor = 0.4 # fraction of rel size before > > > # vacuum > > > #autovacuum_analyze_scale_factor = 0.2 # fraction of rel size before > > > # analyze > > > > I'd cut the above 4 in half. > > > > -- > > Jim Nasby jim@xxxxxxxxx > > EnterpriseDB http://enterprisedb.com 512.569.9461 (cell) > > >
