Re: Table Stats
От | Ron Johnson |
---|---|
Тема | Re: Table Stats |
Дата | |
Msg-id | 1059752822.7505.604.camel@haggis обсуждение исходный текст |
Ответ на | Re: Table Stats (Dennis Gearon <gearond@cvc.net>) |
Список | pgsql-general |
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 -- +-----------------------------------------------------------------+ | Ron Johnson, Jr. Home: ron.l.johnson@cox.net | | Jefferson, LA USA | | | | "I'm not a vegetarian because I love animals, I'm a vegetarian | | because I hate vegetables!" | | unknown | +-----------------------------------------------------------------+
В списке pgsql-general по дате отправления: