On 7 December 2010 18:37, Robert Haas <robertmhaas@xxxxxxxxx> wrote: > On Mon, Dec 6, 2010 at 9:59 PM, Jignesh Shah <jkshah@xxxxxxxxx> wrote: >> That's exactly what I concluded when I was doing the sysbench simple >> read-only test. I had also tried with different lock partitions and it >> did not help since they all go after the same table. I think one way >> to kind of avoid the problem on the same table is to do more granular >> locking (Maybe at page level instead of table level). But then I dont >> really understand on how to even create a prototype related to this >> one. If you can help create a prototype then I can test it out with my >> setup and see if it helps us to catch up with other guys out there. > > We're trying to lock the table against a concurrent DROP or schema > change, so locking only part of it doesn't really work. ÂI don't > really see any way to avoid needing some kind of a lock here; the > trick is how to take it quickly. ÂThe main obstacle to making this > faster is that the deadlock detector needs to be able to obtain enough > information to break cycles, which means we've got to record in shared > memory not only the locks that are granted but who has them. I'm not very familiar with PostgreSQL code but if we're brainstorming... if you're only trying to protect against a small number of expensive operations (like DROP, etc.) that don't really happen often, wouldn't an atomic reference counter be good enough for the purpose (e.g. the expensive operations would spin-wait until the counter is 0)? -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
