[EMAIL PROTECTED] (Csaba Nagy) writes: > On Fri, 2006-04-28 at 15:20, kmh496 wrote: >> 2006-04-28 (ê¸), 14:40 +0200, Csaba Nagy ì°ì길: >> > I placed a cron job to >> > cluster the queue table on it's PK index. >> what does that mean? > > Means execute: > > CLUSTER pk_queue_table ON queue_table; > > See http://www.postgresql.org/docs/8.1/static/sql-cluster.html for more > details on CLUSTER. > > This will actually rebuild the table I guess after it can lock it > exclusively. Due to the fact that the queue transactions are very short > lived, the exclusive lock is fast acquired and the clustering operation > is also fast as the table has only a few entries. > > I'm not sure how this operation can work in the presence of other long > running transactions which did not touch the queue table yet, but it > actually does work, I can confirm that. Is it violating MVCC maybe ?
There is, I believe, a problem there; there is a scenario where data can get "dropped out from under" those old connections. This has been added to the TODO... http://www.postgresql.org/docs/faqs.TODO.html * Make CLUSTER preserve recently-dead tuples per MVCC requirements -- (format nil "[EMAIL PROTECTED]" "cbbrowne" "ntlug.org") http://cbbrowne.com/info/sgml.html Should vegetarians eat animal crackers? ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to [EMAIL PROTECTED] so that your message can get through to the mailing list cleanly
