Added to TODO: * Reduce locking requirements for creating a trigger
http://archives.postgresql.org/pgsql-hackers/2008-06/msg00635.php --------------------------------------------------------------------------- Simon Riggs wrote: > > On Wed, 2008-06-04 at 16:33 -0400, Tom Lane wrote: > > Simon Riggs <[EMAIL PROTECTED]> writes: > > > We have > > > * relhasindex (bool) set by CREATE INDEX but not unset by DROP INDEX > > > * relhasrules (bool) > > > * reltriggers (int2) set by CREATE and DROP, since its an integer > > > > Right. > > > > > If CREATE INDEX can take a Share lock and can update pg_class, why would > > > it not be theoretically possible for CREATE TRIGGER? > > > > It's (probably) theoretically possible, if we replace reltriggers with a > > bool that acts more like relhasindex, ie it's a hint to go look in > > pg_triggers. > > Looking at this area of locking, I've noticed that the locks held by > CREATE TRIGGER are more of a problem than might be apparent. > > * Locks held by CREATE TRIGGER are an issue for trigger-based > replication systems, where triggers are frequently added and removed to > various tables. > > * ALTER TABLE .. ADD FOREIGN KEY holds an AccessExclusiveveLock on > *both* referencing and referenced tables. It does this because we must > add triggers to both tables. So reducing the lock strength required by > CREATE TRIGGER would also allow a reduction in lock strength for adding > FKs. > > So useful steps will be to > > * refactor pg_class code so that CREATE TRIGGER uses an identical > approach to CREATE INDEX > > * reduce lock strength for CREATE TRIGGER and ALTER TABLE ... ADD > FOREIGN KEY so that it takes a ShareLock during > ATAddForeignKeyConstraint() > > * look at how we can reduce lock strength for other ALTER TABLE > subcommands. Not sure how yet. > > -- > Simon Riggs www.2ndQuadrant.com > PostgreSQL Training, Services and Support > > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://enterprisedb.com + If your life is a hard drive, Christ can be your backup. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
