5

次の mysql クエリを実行すると、最初のクエリのタイプが ALL と表示されます。

   mysql> EXPLAIN  
           SELECT one.language_id as filter_id, 
                  one.language_name as filter_name, 
                  two.count as count 
           FROM   books_f9_languages one 
           INNER JOIN (SELECT language_id, 
                       count(*) as count 
                       FROM link_f9_books_lists 
                       WHERE books_list_id IN (1691,1,2,3,4,6,7,8,9,10,11,12,13,14,17,18,19,20,21,22,23,24,25,26,28,29,30,31,32,33,34,35,36,37,43,44,47,51,54,57,58,59,68,71,76,77,86,88,93,94,99,120,125,126,127,133,146,147,148,257,260,261,262,263,264,266,267,268,269,270,271,272,275,276,286,767,768,769,771,772,774,777,779,783,785,786,790,792,799,808,811,813,814,815,819,825,828,829,847,850,852,853,855,856,857,858,862,863,866,869,873,875,882,891,900,907,917,925,930,935,1092,1531,1532,1533,1534,1535,1536,1537,1538,1540,1541,1542,1543,1544,1545,1546,1547,1548,1549,1550,1551,1552,1553,1554,1556,1557,1558,1560,1561,1563,1564,1565,1567,1568,1569,1570,1571,1572,1574,1575,1576,1577,1578,1579,1580,1581,1582,1583,1584,1586,1588,1589,1590,1591,1592,1595,1597,1599,1600,1601,1603,1604,1605,1606,1607,1608,1609,1610,1612,1613,1614,1615,1616,1617,1620,1621,1622,1623,1624,1625,1627,1628,1629,1630,1632,1636,1637,1638,1639,1640,1642,1643,1644,1645,1646,1648,1649,1651,1652,1653,1654,1659,1660,1662,1665,1675,1677,1679,1680,1689,1692,1693,1696,1698,1699,1702,1703,1705,1711,1713,1714,1716,1717,1719,1720,1726,1728,1729,1732,1734,1735,1736,1738,1743,1744,1753,1754,1755,1756,1759,1786,1787,1788,1789,1790,1791,1792,1793,1794,1795,1797,1837,827) GROUP BY language_id) two 
          WHERE one.language_id = two.language_id 
          ORDER BY filter_name;

これが出力です。

+----+-------------+---------------------+--------+---------------+---------------+---------+-----------------+------+-----------------------------------------------------------+
| id | select_type | table               | type   | possible_keys | key           | key_len | ref             | rows | Extra                                                     |
+----+-------------+---------------------+--------+---------------+---------------+---------+-----------------+------+-----------------------------------------------------------+
|  1 | PRIMARY     | <derived2>          | ALL    | NULL          | NULL          | NULL    | NULL            |    5 | Using temporary; Using filesort                           |
|  1 | PRIMARY     | one                 | eq_ref | PRIMARY       | PRIMARY       | 4       | two.language_id |    1 |                                                           |
|  2 | DERIVED     | link_f9_books_lists | range  | books_list_id | books_list_id | 4       | NULL            |  273 | Using where; Using index; Using temporary; Using filesort |
+----+-------------+---------------------+--------+---------------+---------------+---------+-----------------+------+-----------------------------------------------------------+
3 rows in set (0.01 sec)

そのすべてを作成するためにインデックスを作成する必要がある列には、インデックスを使用します。

ありがとう。

4

1 に答える 1

1

派生一時テーブルはインデックスを利用できません。

ORDER BY 句を削除するか、language_id による順序付けを行うと、この問題に対処できます。

または、books_f9_languages テーブルの language_id と language_name に複合インデックスを追加してみてください。

内部クエリを改善するには、link_f9_books_lists テーブルの book_list_id と language_id に複合インデックスを追加します。

于 2012-06-06T20:17:45.250 に答える