On Fri, Sep 14, 2018 at 6:09 PM Kyotaro HORIGUCHI <horiguchi.kyot...@lab.ntt.co.jp> wrote: > At Sat, 4 Aug 2018 14:09:18 +1200, Thomas Munro > <thomas.mu...@enterprisedb.com> wrote in > > Does anyone know why StandbyReleaseLocks() releases all locks if > > passed InvalidTransactionId? When would that happen? > > AFAICS, it used to be used at shutdown time since hot standby was > introduced by efc16ea520 from > ShutdownRecoveryTransactionEnvironment/StandbyReleaseAllLocks. > > c172b7b02e (Jan 23 2012) modified StandbyReleaseAllLocks not to > call StandbyReleaseLocks with InvalidTransactionId and the > feature became useless, and now it is. > > So I think the feature has been obsolete for a long time.
Thank you for this analysis. It looks like dead code that we should remove in master at least. > As a similar thing, the following commands leaves AEL even though > the savepoint is rollbacked. > > BEGIN; SAVEPOINT s; LOCK foo; CHECKPOINT; ROLLBACK TO SAVEPOINT s; > > This is because the checkpoint issues XLOG_STANDBY_LOCK on foo > with the top-transaciton XID. > > Every checkpoint issues it for all existent locks so > RecoveryLockList(s) can be bloated with the same lock entries and > increases lock counts. Although it doesn't seem common to sustain > AELs for a long time so that the length harms, I don't think such > duplication is good. Patch attached. I noticed that too. It seems like it would take a very long time to cause a problem. -- Thomas Munro http://www.enterprisedb.com
