On Wed, Dec 16, 2009 at 1:25 PM, Robert Haas <robertmh...@gmail.com> wrote: > On Wed, Dec 16, 2009 at 1:14 PM, Alvaro Herrera > <alvhe...@commandprompt.com> wrote: >> Robert Haas escribió: >>> On Wed, Dec 16, 2009 at 10:29 AM, Andres Freund <and...@anarazel.de> wrote: >>> > On Wednesday 16 December 2009 16:24:42 Robert Haas wrote: >>> >> > Inserts and deletes follow the same protocol, obtaining an exclusive >>> >> > lock on the row after the one being inserted or deleted. The result >>> >> > of this locking protocol is that a range scan prevents concurrent >>> >> > inserts or delete within the range of the scan, and vice versa. >>> >> > >>> >> > That sounds like it should actually work. >>> >> >>> >> Only if you can guarantee that the database will access the rows using >>> >> some particular index. If it gets to the data some other way it might >>> >> accidentally circumvent the lock. That's kind of a killer in terms of >>> >> making this work for PostgreSQL. >>> > Isnt the whole topic only relevant for writing access? There you have to >>> > access the index anyway. >>> >>> Yeah, I guess you have to insert the new tuple. I guess while you >>> were at it you might check whether the next tuple is locked... >> >> So you'd have to disable HOT updates when true serializability was >> active? > > I thought about that, but I don't think so. HOT only applies to > updates, and predicate locking only applies to inserts. Unless I have > my head in the sand?
Err, no, wait. Predicate locking can apply to updates, but since HOT updates never update an indexed column, I think we might still be OK? ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
