Display the time when the process started waiting for the lock, in pg_locks.
This commit adds new column "waitstart" into pg_locks view. This column
reports the time when the server process started waiting for the lock
if the lock is not held. This information is useful, for example, when
examining the amount of time to wait on a lock by subtracting
"waitstart" in pg_locks from the current time, and identify the lock
that the processes are waiting for very long.
This feature uses the current time obtained for the deadlock timeout
timer as "waitstart" (i.e., the time when this process started waiting
for the lock). Since getting the current time newly can cause overhead,
we reuse the already-obtained time to avoid that overhead.
Note that "waitstart" is updated without holding the lock table's
partition lock, to avoid the overhead by additional lock acquisition.
This can cause "waitstart" in pg_locks to become NULL for a very short
period of time after the wait started even though "granted" is false.
This is OK in practice because we can assume that users are likely to
look at "waitstart" when waiting for the lock for a long time.
Bump catalog version.
Author: Atsushi Torikoshi
Reviewed-by: Ian Lawrence Barwick, Robert Haas, Justin Pryzby, Fujii Masao
Discussion: https://postgr.es/m/a96013dc51cdc56b2a2b84fa8a16a993@oss.nttdata.com
Branch
------
master
Details
-------
https://git.postgresql.org/pg/commitdiff/3b733fcd04195399db56f73f0616b4f5c6828e18
Modified Files
--------------
contrib/amcheck/expected/check_btree.out | 4 ++--
doc/src/sgml/catalogs.sgml | 13 +++++++++++++
src/backend/storage/ipc/standby.c | 24 +++++++++++++++++++++++-
src/backend/storage/lmgr/lock.c | 8 ++++++++
src/backend/storage/lmgr/proc.c | 19 +++++++++++++++++++
src/backend/utils/adt/lockfuncs.c | 9 ++++++++-
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_proc.dat | 6 +++---
src/include/storage/lock.h | 3 +++
src/include/storage/proc.h | 2 ++
src/test/regress/expected/rules.out | 5 +++--
11 files changed, 85 insertions(+), 10 deletions(-)