Simon Riggs wrote: > On Wed, 2007-03-21 at 10:47 -0400, Bruce Momjian wrote: > > > A different idea is to flag the _index_ as using HOT for the table or > > not, using a boolean in pg_index. The idea is that when a new index is > > created, it has its HOT boolean set to false and indexes all tuples and > > ignores HOT chains. Then doing lookups using that index, the new index > > does not follow HOT chains. We also add a boolean to pg_class to > > indicate no new HOT chains should be created and set that to false once > > the new index is created. Then, at some later time when all HOT chains > > are dead, we can enable HOT chain following for the new index and allow > > new HOT chains to be created. > > "enable HOT chain following" would require us to hold an > AccessExclusiveLock on the index.
OK. > We know that solution exists, the question is: at what point would we > ever request that lock? Or would we just wait until that lock is next > taken before enabling it, giving the user no control over when its > taken? A separate DDL command would be effectively the same as what > Pavan has recently suggested. We could just request a lock and if it fails, try again later; it just delays HOT updates, which is not a big problem. Allowing the user to do it via a separate command seems to add nothing. The only thing I could see would be adding an option to CREATE INDEX which waits and then does it. However, given recent comments, I think the xid idea, while more complicated, is better because it has fewer restrictions on when things happen. -- Bruce Momjian <[EMAIL PROTECTED]> http://momjian.us EnterpriseDB http://www.enterprisedb.com + If your life is a hard drive, Christ can be your backup. + ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend