On Mon, Aug 3, 2015 at 2:15 AM, Michael Paquier <michael.paqu...@gmail.com> wrote: > > On Sat, Aug 1, 2015 at 9:20 PM, Andres Freund wrote: > > On August 1, 2015 2:17:24 PM GMT+02:00, Michael Paquier wrote: > >>> For instance, if you told me to choose between ShareLock and > >>> ShareUpdateExclusiveLock I wouldn't know which one is strongest. I > >>> don't it's sensible to have the "lock mode compare" primitive > >>honestly. > >>> I don't have any great ideas to offer ATM sadly. > >> > >>Yes, the thing is that lowering the lock levels is good for > >>concurrency, but the non-monotony of the lock levels makes it > >>impossible to choose an intermediate state correctly. > > > > How about simply acquiring all the locks individually of they're different types? These few acquisitions won't matter. > > As long as this only applies on master, this may be fine... We could > basically pass a LOCKMASK to the multiple layers of tablecmds.c > instead of LOCKMODE to track all the locks that need to be taken, and > all the relations open during operations. Would it be worth having > some routines like relation_multi_[open|close]() as well? Like that: > Relation[] relation_multi_open(relation Oid, LOCKMASK): > void relation_multi_close(Relation[]); > > If we do something, we may consider patching as well 9.5, it seems to > me that tablecmds.c is broken by assuming that lock hierarchy is > monotone in AlterTableGetLockLevel(). >
Hey guys, Are you sure we need to do all this changes just to check the highest locklevel based on the reloptions? Or I misunderstood the whole thing? Maybe we just check the DoLockModeConflict in the new method GetReloptionsLockLevel and if true then fallback to AccessExclusiveLock (as Michael suggested in a previous email). Regards, *** This work is funded by Zenvia Mobile Results (http://www.zenvia.com.br) -- Fabrízio de Royes Mello Consultoria/Coaching PostgreSQL >> Timbira: http://www.timbira.com.br >> Blog: http://fabriziomello.github.io >> Linkedin: http://br.linkedin.com/in/fabriziomello >> Twitter: http://twitter.com/fabriziomello >> Github: http://github.com/fabriziomello