Как узнать самые ненужные индексы в mysql

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 /* unique indexes are perfect anyway */
ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME          /* DESC for best non-unique indexes */
LIMIT 10;

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 /* unique indexes are perfect anyway */

ORDER BY `sel %`, s.TABLE_SCHEMA, s.TABLE_NAME /* DESC for best non-unique indexes */

LIMIT 10;

Это из лекции товарища Jay Pipes

Daily Archives: 19.10.2009

Как узнать самые ненужные индексы в mysql