On 04/13/2014 12:58 PM, Torsten Förtsch wrote: > Hi, > > currently, ALTER TABLE VALIDATE CONSTRAINT for foreign key constraints > acquires an AccessExclusiveLock on the referencing table. > > Why? > > If the constraint is in place but not validated (ADD CONSTRAINT ... NOT > VALID) it already prevents new modifications from violating the constraint. > > The code that is called to validate the constraint, RI_Initial_Check, > contains this comment: > > * We expect that the caller has made provision to prevent any problems > * caused by concurrent actions. This could be either by locking rel and > * pkrel at ShareRowExclusiveLock or higher, or by otherwise ensuring > * that triggers implementing the checks are already active. > * Hence, we do not need to lock individual rows for the check. > > Doesn't the presence of the NOT VALID constraint qualify as "otherwise > ensuring that triggers implementing the checks are already active"? > > Is there any deeper reason? Or is it simply not implemented yet? > Actually, it is implemented yet. http://www.postgresql.org/message-id/E1WWovD-0004Ts-66@xxxxxxxxxxxxxxxxxxxxxx It'll be in 9.4. -- Vik -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
