On Thu, Oct 29, 2009 at 07:53:25PM +0300, Sergey Petrunya wrote: > ... taxonomic_units1 AS O1 > LEFT OUTER JOIN taxonomic_units1 AS O2 > ON O1.tsn = O2.parent_tsn > > current optimizer has only one option(*): use Nested-Loops Join algorthm, with > the outer table being the first one. That is, it will execute these loops: > > for each record from O1 > for each record in O2 such that O1.tsn = O2.parent_tsn > ... > > this makes it clear that index on O1.tsn will not be useful. You need indexes > on parent_tsn column. I meant, one index over taxonomic_units1.parent_tsn .
BR Sergey -- Sergey Petrunia, Software Developer Monty Program AB, http://askmonty.org Blog: http://s.petrunia.net/blog -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/mysql?unsub=arch...@jab.org
