Strange use of the index in Mysql
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Published on 2010-04-05T07:33:38Z
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2010/04/05
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explain SELECT feed_objects.* FROM feed_objects WHERE (feed_objects.feed_id IN (165,160,159,158,157,153,152,151,150,149,148,147,129,128,127,126,125,124,122,121,120,119,118,117,116,115,114,113,111,110)) ;
+----+-------------+--------------+------+---------------+------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+------+---------------+------+---------+------+------+-------------+
| 1 | SIMPLE | feed_objects | ALL | by_feed_id | NULL | NULL | NULL | 188 | Using where |
+----+-------------+--------------+------+---------------+------+---------+------+------+-------------+
Not used index 'by_feed_id'
But when I point less than the values in the "WHERE" - everything is working right
explain SELECT feed_objects.* FROM feed_objects WHERE (feed_objects.feed_id IN (165,160,159,158,157,153,152,151,150,149,148,147,129,128,127,125,124)) ;
+----+-------------+--------------+-------+---------------+------------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+--------------+-------+---------------+------------+---------+------+------+-------------+
| 1 | SIMPLE | feed_objects | range | by_feed_id | by_feed_id | 9 | NULL | 18 | Using where |
+----+-------------+--------------+-------+---------------+------------+---------+------+------+-------------+
Used index 'by_feed_id'
What is the problem?
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