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POMySQL How can I speed up this SELECT query?
 

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  1. POMySQL How can I speed up this SELECT query?
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    <p>I have a very large table of over 9 million rows and in my software I need to rapidly do select queries on it in a loop. The problem is that the queries take almost 4 seconds to complete. Here is one of the queries (they are all similar in that they all have the same WHERE clause that is slowing them down:</p> <pre><code>SELECT MIN(id) FROM `04c1Tg0M` WHERE `tried` = 0; </code></pre> <p>I'm using the tried column as a boolean. the value is either 1 or 0. Here is the EXPLAIN from that query:</p> <pre><code>--------+--------------------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+----------+-------+---------------+------+---------+------+---------+--------------------------+ | 1 | SIMPLE | 04c1Tg0M | index | NULL | pdex | 158 | NULL | 9275107 | Using where; Using index | +----+-------------+----------+-------+---------------+------+---------+------+---------+--------------------------+ </code></pre> <p>Here is the table structure:</p> <pre><code>CREATE TABLE `04c1Tg0M` ( `id` int(20) NOT NULL AUTO_INCREMENT, `username` varchar(50) NOT NULL, `tried` tinyint(1) DEFAULT '0', PRIMARY KEY (`id`), KEY `pdex` (`username`,`id`,`tried`) ) ENGINE=MyISAM AUTO_INCREMENT=9275108 DEFAULT CHARSET=utf8 </code></pre> <p>Here is the output of show indes:</p> <pre><code>| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | +----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ | 04c1Tg0M | 0 | PRIMARY | 1 | id | A | 9275107 | NULL | NULL | | BTREE | | | 04c1Tg0M | 1 | pdex | 1 | username | A | 9275107 | NULL | NULL | | BTREE | | | 04c1Tg0M | 1 | pdex | 2 | id | A | 9275107 | NULL | NULL | | BTREE | | | 04c1Tg0M | 1 | pdex | 3 | tried | A | 9275107 | NULL | NULL | YES | BTREE | | +----------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+ </code></pre> <p>And here is the output from the query in question:</p> <pre><code>+---------+ | MIN(id) | +---------+ | 1 | +---------+ 1 row in set (3.76 sec) </code></pre> <p>I need to drastically reduce the query time. Any help is greatly appreciated.</p>
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      1. POMySQL How can I speed up this SELECT query?
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    1. COCan you post the output of `EXPLAIN SELECT`? Do you know what percentage of the rows have `tried = 0` versus `tried = 1`?
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      1. POMySQL How can I speed up this SELECT query?
      1. USMark Byers
 

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