Tom Lane wrote: > Bruce Momjian <[EMAIL PROTECTED]> writes: > > Tom Lane wrote: > >> ... and it would give the wrong answers. Unless the cache is somehow > >> snapshot-aware, so that it can know which other transactions should be > >> included in your count. > > > The cache is an ordinary table, with xid's on every row. I meant it > > would require no index/heap scans of the large table --- it would still > > require a scan of the "count" table. > > Oh, that idea. Yeah, I think we had concluded it might work. You'd > better make the TODO item link to that discussion, because there's sure > been plenty of discussion of ideas that wouldn't work.
OK, I beefed up the TODO: * Use a fixed row count and a +/- count with MVCC visibility rules to allow fast COUNT(*) queries with no WHERE clause(?) I can always give the details if someone asks. It doesn't seem complex enough for a separate TODO.detail item. -- 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 8: explain analyze is your friend