/* SQL script to grab the worst performing indexes in all databases */ SELECT t.TABLE_SCHEMA AS `db` , t.TABLE_NAME AS `table` , s.INDEX_NAME AS `index name` , s.COLUMN_NAME AS `field name` , s.SEQ_IN_INDEX `seq in index` , s2.max_columns AS `# cols` , s.CARDINALITY AS `card` , t.TABLE_ROWS AS `est rows` , ROUND(((s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) * 100), 2) AS `sel %` FROM INFORMATION_SCHEMA.STATISTICS s INNER JOIN INFORMATION_SCHEMA.TABLES t ON s.TABLE_SCHEMA = t.TABLE_SCHEMA AND s.TABLE_NAME = t.TABLE_NAME INNER JOIN ( SELECT TABLE_SCHEMA , TABLE_NAME , INDEX_NAME , MAX(SEQ_IN_INDEX) AS max_columns FROM INFORMATION_SCHEMA.STATISTICS WHERE TABLE_SCHEMA != 'mysql' GROUP BY TABLE_SCHEMA, TABLE_NAME, INDEX_NAME ) AS s2 ON s.TABLE_SCHEMA = s2.TABLE_SCHEMA AND s.TABLE_NAME = s2.TABLE_NAME AND s.INDEX_NAME = s2.INDEX_NAME WHERE t.TABLE_SCHEMA != 'mysql' /* Filter out the mysql system DB */ AND t.TABLE_ROWS > 10 /* Only tables with some rows */ AND s.CARDINALITY IS NOT NULL /* Need at least one non-NULL value in the field */ AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00 /* Selectivity < 1.0 b/c unique indexes are perfect anyway */ ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME /* Switch to `sel %` DESC for best non-unique indexes */ LIMIT 20; /* Change this row limit to whatever you prefer ... */