ALTER TABLE ... DISABLE TRIGGER vs. AccessExclusiveLock
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From: Robert Haas on 27 Jul 2010 15:36 On Tue, Jul 27, 2010 at 3:07 PM, James Robinson <jlrobins(a)socialserve.com> wrote: > Experience and a read through backend/commands/tablecmds.c's AlterTable() > indicate that ALTER TABLE ... DISABLE TRIGGER obtains an exclusive lock on > the table (as does any ALTER TABLE). > > Blocking other readers from a table when we've, within the body of a > transaction performing a bulk update operation where we don't want / need > triggers to fire, seems at first glance to be over-kill. I can see how > AlterTable()'s complex logic is made less complex through 'get and keep a > big lock', since most of its operational modes really do need exclusive > access, but is it strictly required for ... DISABLE / REENABLE TRIGGER? > > Could, say, RowExclusiveLock hypothetically provide adequate protection, > allowing concurrent reads, but blocking out any other writers (for ENABLE / > DISABLE TRIGGER) -- such as if driven through a new statement other than > ALTER TABLE -- such as "DISABLE TRIGGER foo ON tbar" ? Funny you should mention this. There is a pending patch to do something very much along these line. https://commitfest.postgresql.org/action/patch_view?id=347 -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise Postgres Company -- Sent via pgsql-hackers mailing list (pgsql-hackers(a)postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers |