On 22 January 2014 04:42, Rajeev rastogi <rajeev.rast...@huawei.com> wrote: > > On 31st December 2013, Christian Kruse Wrote: > >> Hi there, >> >> I created two patches improving the log messages generated by >> log_lock_waits. The first patch shows the process IDs holding a lock we >> try to acquire (show_pids_in_lock_log.patch), sample output >> (log_lock_waits=on required): >> >> session 1: BEGIN; LOCK TABLE foo IN SHARE MODE; session 2: BEGIN; LOCK >> TABLE foo IN SHARE MODE; session 3: BEGIN; LOCK TABLE foo IN EXCLUSIVE >> MODE; >> >> Output w/o patch: >> >> LOG: process 13777 still waiting for ExclusiveLock on relation 16385 >> of database 16384 after 1000.030 ms >> >> Output with patch: >> >> LOG: process 13777 still waiting for ExclusiveLock on relation 16385 >> of database 16384 after 1000.030 ms >> CONTEXT: processes owning lock: 13775, 13776 > > I am reviewing this patch. The idea seems to be reasonable. > Following are my first level observation: > > 1. I find a issue in following scenario: > > session 1 with process id X: BEGIN; LOCK TABLE foo IN SHARE MODE; > session 2 with process id Y: BEGIN; LOCK TABLE foo IN EXCLUSIVE MODE; > session 3 with process id Z: BEGIN; LOCK TABLE foo IN SHARE MODE; > > On execution of LOCK in session-3, as part of log it will display as: > processes owning lock: X, Y > But actually if we see Y has not yet own the lock, it is still > waiting with higher priority. > It may mislead user. > May be we should change message to give all meaning i.e. which > process is owning lock and > Which process is already in queue.
Perhaps this? CONTEXT: lock owner XXXX request queue XXX, XXX, XXX, etc > 2. Can we give a better name to new variable 'buf1'? > > 3. Do we need to take performance reading to see if any impact? Don't think so. Diagnosing problems will help performance, not hinder it > 4. Do we require documentation? Don't think so. -- Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
