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POsame query, dramatic different performances on different data. MySQL
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7507904
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2011-09-21T23:27:05.170
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2011-09-22T16:35:02.843
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2011-09-22T16:35:02.843
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Body
So, I have this huge database with 40 Millions entries. the query is a simple (a_view is a view!) <pre><code>select * from a_view where id > x LIMIT 10000 </code></pre> this is the behavior I get: If x is a little number (int) the query is super fast. when x > 29 Millions the query starts to take minutes. if it is closer to 30 Millions it takes hours. and so on... why is that? what can I do to avoid this? I am using InnoDB as engine, tables have indexes. the value of the limit is a critical one, it affects performances. if it is small the query is always fast. but if x is close to 30Millions then I need to be very careful to set it not too big (less than 300 hundreds), and still it is quite slow, but doesn't take forever If you need more details, feel free to ask. EDIT: here is the explain <pre> +----+-------------+-------+--------+-----------------+---------+---------+---------------------+---------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+-------+--------+-----------------+---------+---------+---------------------+---------+-------------+ | 1 | SIMPLE | aH | index | PRIMARY | PRIMARY | 39 | NULL | 3028439 | Using index | | 1 | SIMPLE | a | eq_ref | PRIMARY | PRIMARY | 4 | odb.aH.albumID | 1 | Using where | | 1 | SIMPLE | aHT | ref | PRIMARY,albumID | albumID | 4 | odb.a.albumID | 4 | | | 1 | SIMPLE | t | eq_ref | PRIMARY | PRIMARY | 4 | odb.aHT.id | 1 | Using where | | 1 | SIMPLE | g | eq_ref | PRIMARY | PRIMARY | 4 | odb.t.genre | 1 | | | 1 | SIMPLE | ar | eq_ref | PRIMARY | PRIMARY | 4 | odb.t.artist | 1 | | +----+-------------+-------+--------+-----------------+---------+---------+---------------------+---------+-------------+ </pre>
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<mysql><performance><limit>
Title
same query, dramatic different performances on different data. MySQL
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A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.