MySQL ignore mon index

Question

Je suis en cours d'exécution de la requête suivante dans MYSQL

select distinct straight_join 
    cu.entryid entryid, 
    t0.tokpos starting_position, 
    t3.tokpos ending_position, 
    t0.idxsent idxsent, 
    'TOKENS_44_340' tablename 
from 
    TOKENS_44_340 t0, 
    constraints_appraisal cu, 
    TOKENS_44_340 t1, 
    TOKENS_44_340 t2, 
    TOKENS_44_340 t3 
where 
t0.token_surface = cu.token_0 
and (cu.pos_0 is null OR t0.penntag like concat(cu.pos_0,'%')) 
and t1.token_surface = cu.token_1 
and (cu.pos_1 is null OR t1.penntag like concat(cu.pos_1,'%')) 
and t2.token_surface = cu.token_2 
and (cu.pos_2 is null OR t2.penntag like concat(cu.pos_2,'%')) 
and t3.token_surface = cu.token_3 
and (cu.pos_3 is null OR t3.penntag like concat(cu.pos_3,'%')) 
and t0.tokpos = t1.tokpos - 1 
and t1.tokpos = t2.tokpos - 1 
and t2.tokpos = t3.tokpos - 1 
and cu.token_4 is null 
and cu.token_5 is null 
and cu.token_6 is null 
and cu.token_7 is null 
and cu.token_8 is null 
and cu.token_9 is null; 

MySQL me donne le plan de requête suivante pour cette requête:

+----+-------------+-------+------+---------------------------------------+------------------------+---------+------+------+-----------------+ 
| id | select_type | table | type | possible_keys       | key     | key_len | ref | rows | Extra   | 
+----+-------------+-------+------+---------------------------------------+------------------------+---------+------+------+-----------------+ 
| 1 | SIMPLE  | t0 | ALL | PRIMARY,TOKENS_44_340_index_44,tokpos | NULL     | NULL | NULL | 49 | Using temporary | 
| 1 | SIMPLE  | cu | ALL | NULL         | NULL     | NULL | NULL | 7907 | Using where  | 
| 1 | SIMPLE  | t1 | ref | PRIMARY,TOKENS_44_340_index_44,tokpos | TOKENS_44_340_index_44 | 399  | func | 4 | Using where  | 
| 1 | SIMPLE  | t2 | ref | PRIMARY,TOKENS_44_340_index_44,tokpos | TOKENS_44_340_index_44 | 399  | func | 4 | Using where  | 
| 1 | SIMPLE  | t3 | ref | TOKENS_44_340_index_44    | TOKENS_44_340_index_44 | 399  | func | 4 | Using where  | 
+----+-------------+-------+------+---------------------------------------+------------------------+---------+------+------+-----------------+ 
5 rows in set (0.00 sec) 

Comme vous pouvez le voir, MySQL ne pas même autant que reconnaître l'existence de mon index token_0 sur constraints_appraisal(token_0). Une idée de pourquoi ça ignore mon index, et que puis-je faire? J'utilise mysql 5.0.51a-24 + lenny4 pour Debian stable.

P.S. Je sais que je pourrais accélérer l'exécution de cette requête en supprimant la contrainte straight_join et la laisser utiliser la token_surface index sur t0, mais elle ne serait pas aussi rapide qu'elle pourrait l'être en utilisant l'index token_0 sur constraints_appraisal. J'ai ajouté le straight_join afin que je puisse faire apparaître plus clairement mon problème spécifique, et je prévois de le supprimer lorsque l'index fonctionne correctement.

mysql> describe TOKENS_44_340; 
+---------------+--------------+------+-----+---------+-------+ 
| Field   | Type   | Null | Key | Default | Extra | 
+---------------+--------------+------+-----+---------+-------+ 
| tokPos  | int(11)  | NO | PRI | NULL |  | 
| linePos  | int(11)  | YES |  | NULL |  | 
| EOLs   | int(11)  | YES |  | NULL |  | 
| idxsent  | int(11)  | YES |  | NULL |  | 
| possent  | int(11)  | YES |  | NULL |  | 
| brilltag  | int(11)  | YES |  | NULL |  | 
| token_surface | varchar(132) | YES | MUL | NULL |  | 
| wordLen  | int(11)  | YES |  | NULL |  | 
| capitalized | int(11)  | YES |  | NULL |  | 
| wordType  | int(11)  | YES |  | NULL |  | 
| numDigit  | int(11)  | YES |  | NULL |  | 
| numPunc  | int(11)  | YES |  | NULL |  | 
| numAlpha  | int(11)  | YES |  | NULL |  | 
| maxRep  | int(11)  | YES |  | NULL |  | 
| pre1   | varchar(132) | YES |  | NULL |  | 
| pre2   | varchar(132) | YES |  | NULL |  | 
| pre3   | varchar(132) | YES |  | NULL |  | 
| pre4   | varchar(132) | YES |  | NULL |  | 
| suf1   | varchar(132) | YES |  | NULL |  | 
| suf2   | varchar(132) | YES |  | NULL |  | 
| suf3   | varchar(132) | YES |  | NULL |  | 
| suf4   | varchar(132) | YES |  | NULL |  | 
| dep_gov  | int(11)  | YES | MUL | NULL |  | 
| dep_rel  | varchar(20) | YES | MUL | NULL |  | 
| penntag  | varchar(30) | YES |  | NULL |  | 
+---------------+--------------+------+-----+---------+-------+ 
25 rows in set (0.04 sec) 

mysql> describe constraints_appraisal; 
+---------------+--------------+------+-----+---------+-------+ 
| Field   | Type   | Null | Key | Default | Extra | 
+---------------+--------------+------+-----+---------+-------+ 
| entryid  | int(11)  | NO | PRI | 0  |  | 
| context  | varchar(50) | YES |  | NULL |  | 
| syntax  | int(11)  | YES |  | NULL |  | 
| token_0  | varchar(50) | YES | MUL | NULL |  | 
| pos_0   | varchar(50) | YES |  | NULL |  | 
| porter_0  | varchar(50) | YES | MUL | NULL |  | 
| token_1  | varchar(50) | YES |  | NULL |  | 
| pos_1   | varchar(50) | YES |  | NULL |  | 
| porter_1  | varchar(50) | YES |  | NULL |  | 
| token_2  | varchar(50) | YES |  | NULL |  | 
| pos_2   | varchar(50) | YES |  | NULL |  | 
| porter_2  | varchar(50) | YES |  | NULL |  | 
| token_3  | varchar(50) | YES |  | NULL |  | 
| pos_3   | varchar(50) | YES |  | NULL |  | 
| porter_3  | varchar(50) | YES |  | NULL |  | 
| token_4  | varchar(50) | YES |  | NULL |  | 
| pos_4   | varchar(50) | YES |  | NULL |  | 
| porter_4  | varchar(50) | YES |  | NULL |  | 
| token_5  | varchar(50) | YES |  | NULL |  | 
| pos_5   | varchar(50) | YES |  | NULL |  | 
| porter_5  | varchar(50) | YES |  | NULL |  | 
| token_6  | varchar(50) | YES |  | NULL |  | 
| pos_6   | varchar(50) | YES |  | NULL |  | 
| porter_6  | varchar(50) | YES |  | NULL |  | 
| token_7  | varchar(50) | YES |  | NULL |  | 
| pos_7   | varchar(50) | YES |  | NULL |  | 
| porter_7  | varchar(50) | YES |  | NULL |  | 
| token_8  | varchar(50) | YES |  | NULL |  | 
| pos_8   | varchar(50) | YES |  | NULL |  | 
| porter_8  | varchar(50) | YES |  | NULL |  | 
| token_9  | varchar(50) | YES |  | NULL |  | 
| pos_9   | varchar(50) | YES |  | NULL |  | 
| porter_9  | varchar(50) | YES |  | NULL |  | 
| token_surface | varchar(200) | YES |  | NULL |  | 
| fileid  | varchar(100) | YES |  | NULL |  | 
+---------------+--------------+------+-----+---------+-------+ 
35 rows in set (0.06 sec) 

mysql> show index from constraints_appraisal; 
+-----------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| Table     | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | 
+-----------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
| constraints_appraisal |   0 | PRIMARY |   1 | entryid  | A   |  7907 |  NULL | NULL |  | BTREE  |   | 
| constraints_appraisal |   1 | token_0 |   1 | token_0  | A   |  NULL |  NULL | NULL | YES | BTREE  |   | 
| constraints_appraisal |   1 | porter_0 |   1 | porter_0 | A   |  NULL |  NULL | NULL | YES | BTREE  |   | 
+-----------------------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ 
3 rows in set (0.05 sec) 

Answer 1

Il semble que le problème est que les deux tables se trouvent dans des jeux de caractères différents.

• TOKENS_44_340 est dans utf8
• constraints_appraisal est dans latin1