Re: Eliminating unnecessary left joins
Tom Lane <tgl@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ottó Havasvölgyi <havasvolgyi.otto@gmail.com>
Cc: pgsql-hackers@postgresql.org
Date: 2007-04-06T23:38:39Z
Lists: pgsql-hackers
"=?ISO-8859-1?Q?Ott=F3_Havasv=F6lgyi?=" <havasvolgyi.otto@gmail.com> writes: > When using views built with left joins, and then querying against these > views, there are a lot of join in the plan that are not necessary, because I > don't select/use any column of each table in the views every time. Tables > that are left joined and never referenced anywhere else in the query should > be removed from the plan. That might cause you to get the wrong number of copies of some rows --- what if a row of the left table should join to multiple rows on the right? regards, tom lane