SELECT
t.TABLE_SCHEMA AS `db`
, t.TABLE_NAME AS `table`
, s.INDEX_NAME AS `inde 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
/* Filter out the mysql system DB */
WHERE t.TABLE_SCHEMA != 'mysql'
/* Only tables with some rows */
AND t.TABLE_ROWS > 10
/* Need at least one non-NULL value in the field */
AND s.CARDINALITY IS NOT NULL
/* unique indexes are perfect anyway */
AND (s.CARDINALITY / IFNULL(t.TABLE_ROWS, 0.01)) < 1.00
/* DESC for best non-unique indexes */
ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME
LIMIT 10;

A essayer de toute urgence si vous avez des problèmes de performance.

Source : Jay Pipes

Cet article a été publié le Friday 11 January 2008 à 10.53 pm et est classé dans MySQL. Vous pouvez suivre les réponses reçues par cet article grâce au fil RSS 2.0. Vous pouvez laisser un commentaire, ou faire un trackback depuis votre site.