Am Donnerstag, 9. November 2006 15:51 schrieb Becker, Holger: > Michael Ruf wrote: > > Hi, > > > > i've experienced a mysterious performance problem with MaxDB 7.5.00 26 > > > > The following statement performs a full table scan when the > > subquery returns > > no result: > > > > delete from cx_click where link_id in ( select link_id from > > cX_link where > > task_id = ? ) > > > > Is this a bug? > > > > > > regards > > Michael > > Hi, > > for MaxDB link_id have to be the first or only column of the key or an > index to avoid the full table scan in this case. >
click_id is the primary key and there is an index on the link_id column. link_id is of type INTEGER. The index is used while the subselects returns a result delete from cx_click where link_id in ( 1234, 3454, 231 ) but not if the subselect return no result delete from cx_click where link_id in ( ) I think that the optimizer should recognize that the in clause is empty and there will be no match. Or am i missunderstaning the semantic of an empty "in clause". regards Michael ---------------------------------------------------- -- MaxDB Discussion Mailing List For list archives: http://lists.mysql.com/maxdb To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
