Actually, it's a slightly different problem - a very uneven distribution of values on a column, not a small number of possible values like a bitmap index is for.
In my opinion, this is a pretty useless feature, I mean the whole *point* of the optimizer is to see things like that and do a full table scan when it's going to be faster. I guess I can see the point if the row is only *added* to the index if it matches the WHERE clause. That'd speed up the index management as well. Dean Harding. > -----Original Message----- > From: Daniel Koch [mailto:[EMAIL PROTECTED]] > Sent: Tuesday, 19 November 2002 5:58 am > To: [EMAIL PROTECTED] > Cc: Egor Egorov; Neulinger, Nathan; Jeremy Zawodny > Subject: Re: feature suggestion - indexes with "where" clause or similar > > On Mon, 2002-11-18 at 12:29, Jeremy Zawodny wrote: > > > > If I've got you right status can have values 0 or 1. In this case > > > you can just use " SELECT ... WHERE status=1 .." (index wil be used) > > > or "SELECT .. WHERE status=0 .." (index will not be used, because > > > scan the whole table will be faster to retrieve 99,9% of rows) > > > depends on what you want to get. > > > > I'd like to second Nathan's request. > > > > Just because MySQL is smart enough to not use an index when 99% of the > > rows would match doesn't mean that this is an unnecessary request. > > It'd be a great optimization it MySQL could "know" not to bother > > indexing those records. It'd save a lot of space and CPU time on > > larger data sets. > > > > Jeremy > > > > I think this problem could be solved by implementing a BITMAP index, > like Oracle. They're perfect for indexing boolean true/false columns or > any column that has a small number of possible values. > > > > > > > > -- > > Daniel Koch <[EMAIL PROTECTED]> > > > --------------------------------------------------------------------- > Before posting, please check: > http://www.mysql.com/manual.php (the manual) > http://lists.mysql.com/ (the list archive) > > To request this thread, e-mail <[EMAIL PROTECTED]> > To unsubscribe, e-mail <mysql-unsubscribe- > [EMAIL PROTECTED]> > Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php --------------------------------------------------------------------- Before posting, please check: http://www.mysql.com/manual.php (the manual) http://lists.mysql.com/ (the list archive) To request this thread, e-mail <[EMAIL PROTECTED]> To unsubscribe, e-mail <[EMAIL PROTECTED]> Trouble unsubscribing? Try: http://lists.mysql.com/php/unsubscribe.php
