Re: Table Stats

On Fri, 2003-08-01 at 10:21, Dennis Gearon wrote:
> There has been discussion of making select count(*) fast. Is this
> in 7.4 or will it be in 7.5?

Internal hash tables, I believe, are used in 7.4 to speed up these
kinds of aggregates:

select foo, count(*)
from bar
where wiggle='wabble'
group by foo;

> Ron Johnson wrote:
>
> > On Thu, 2003-07-31 at 23:23, Dennis Gearon wrote:
> >
> >>It will only be at a given point in time, since datasbases are by
> >>design, realtime/concurrent applications.
> >>
> >>do:
> >>
> >>SELECT COUNT(*) FROM table_name;
> >>
> >>Should give you what you want.
> >
> >
> > It'll give him what he wants, but not quickly, if it's a 10/20/etc
> > M row table.
> >
> > One hack is:
> > CREATE TABLE T_CARDINALITY (
> > RELATION_NAME CHAR(31) PRIMARY KEY,
> > CARDINALITY BIGINT );
> >
> > Then put ON INSERT/ON DELETE triggers on each table you want to
> > track that increment/decrement T_CARDINALITY.CARDINALITY at the
> > appropriate moment.
> >
> >
> >>Jeff Davidson wrote:
> >>
> >>
> >>>Hi!
> >>>
> >>>Is there any quick way to determine how many rows exist in a given table?
> >
> >
>
>
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
> joining column's datatypes do not match
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