On Thu, Feb 16, 2006 at 01:08:40PM -0800, Kashmira Patel (kupatel) wrote: > So I would have to put in lots of rows of data in the table before using > the explain command?
Well, no, but you won't get useful information without it. PostgreSQL has a cost-based optimizer. The query plan is affected by the nature of your data. That's what the ANALYZE command (on its own, or with VACUUM) is for. A > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Andrew Sullivan > Sent: Thursday, February 16, 2006 12:39 PM > To: [email protected] > Subject: Re: [SQL] Using EXPLAIN-ANALYZE > > On Thu, Feb 16, 2006 at 12:07:10PM -0800, Kashmira Patel (kupatel) > wrote: > > Hi all, > > I am pretty new to using Postrgres, and have been looking at the > > messages in this forum for a while. I have noticed that the use of > > EXPLAIN-ANALYZE is recommended quite a lot. I read the Postgres docs, > > but am not quite sure I understand how this works. Is there some > > tutorial or any other documentation how this can be used? > > Well, here's the short version: > > EXPLAIN [query] tells you what the planner _thinks_ it should do. > > EXPLAIN ANALYZE [query] tells you what the planner thinks it should do, > and also executes the query and reports back how long every step took, > how many rows were returned, &c. (For this reason, you want to wrap it > in BEGIN;...;ROLLBACK; if it changes data.) > > For more, see the EXPLAIN EXPLAINED tutorial on techdocs.postgresql.org > (<http://techdocs.postgresql.org/oscon2005/robert.treat/OSCON_Explaining > _Explain_Public.sxi>) > > A > > -- > Andrew Sullivan | [EMAIL PROTECTED] > In the future this spectacle of the middle classes shocking the avant- > garde will probably become the textbook definition of Postmodernism. > --Brad Holland > > ---------------------------(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 -- Andrew Sullivan | [EMAIL PROTECTED] The fact that technology doesn't work is no bar to success in the marketplace. --Philip Greenspun ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
