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                        |
  [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

Reply via email to