Yes, I think these are all correct, except I am not positive FOR UPDATE NOWAIT will be in 7.5 unless someone codes it.
--------------------------------------------------------------------------- Luis P Caamano wrote: > > I've researched the recent discussions about statement_timeout > and NOWAIT and I'd like to confirm my understanding of the > situation before acting on it. Please let me know if the > following statements are true: > > - LOCK TABLE ... NOWAIT has been checked in and will be available > in 7.5 > > - SELECT ... FOR UPDATE NOWAIT is in the TODO list (among other > NOWAIT commands) but it will also be available in 7.5 > > - Using "SET LOCAL statement_timeout=xxx" can be used before > "SELECT ... FOR UPDATE" to emulate NOWAIT when the select > is simple and involves a relatively small number of rows. > That is, the following: > > BEGIN; > SET LOCAL statement_timeout=3000; > SELECT ... FOR UPDATE; -- (1 row) > COMMIT; > > will be equivalent to: > > BEGIN; > SELECT ... FOR UPDATE NOWAIT; > COMMIT; > > - The NOWAIT feature will be able to handle select-for-updates > that involve many rows better than statement_timeout because > it will track timeouts on a row by row basis, which eliminates > false positives. That is, if the statement_timeout is too > short for the select, it might fail before finishing the select > instead of failing because of locked row. > > - The error raised by statement_timeout and NOWAIT will be the > same. > > Basically, I'd like to write low level code that implements > NOWAIT in the application using statement_timeout. Later on, > 7.5, I'd be able to reimplement the low level functions using > NOWAIT without having to change the higher level code. > > Your thoughts and comments are appreciated. > > Thanks > > Luis P Caamano > Atlanta, GA, USA > > > ---------------------------(end of broadcast)--------------------------- > TIP 7: don't forget to increase your free space map settings > -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 359-1001 + If your life is a hard drive, | 13 Roberts Road + Christ can be your backup. | Newtown Square, Pennsylvania 19073 ---------------------------(end of broadcast)--------------------------- TIP 6: Have you searched our list archives? http://archives.postgresql.org
