materialized path performance problem
Posted by: Marcin Lulek
Date: July 11, 2006 05:17AM

i have a table like this ( it stores categories in tree structure )
CREATE TABLE `instr_kategorie` (
`id` mediumint(8) unsigned NOT NULL auto_increment,
`name` varchar(100) NOT NULL default '',
`description` varchar(150) NOT NULL default '',
`depth` smallint(5) unsigned NOT NULL default '0',
`path` varchar(255) NOT NULL default '',
`visible` tinyint(1) NOT NULL default '0',
`sort` tinyint(1) unsigned NOT NULL default '0',
KEY `visible` (`visible`),
KEY `path` (`path`),
KEY `depth` (`depth`)

random row from the table:
(83, 'djjhgj', 'opis', 10, '1_2_4_7_58_61_62_63_82_83', 1, 0),

and the problem is when i try to pull out all items form the database and count all indirect children of an item.


SELECT k. * , COUNT( ) AS children FROM instr_kategorie AS k LEFT JOIN instr_kategorie AS d ON d.path LIKE CONCAT( k.path, '_%' ) GROUP BY ORDER BY k.path ASC

the query works but is VERY slow

it executes 0.0266s for 70 rows :/ how can i optimise the query ?

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materialized path performance problem
July 11, 2006 05:17AM

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