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[Blog] InnoDB: Warning: a long semaphore wait [Original] 2011-2-7 4:02pm

error: MySQL is keeping restarted and generated a lot of error message on the InnoDB datafile.

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Section:MySQL DBA | Read:3945 | Comment:0 | Rating:0%

[Blog] Bad performance on a large offet and coving index [Original] 2010-4-1 11:50am

A statement with an offset got bad performance when the offset getting bigger and bigger. The performance was improved after changing it to use the primary key.

 

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[Study Notes] The query optimizer and Last_query_cost [Original] 2009-11-18 12:15pm
MySQL uses a cost-based optimizer, which means it tries to predict the cost of variousexecution plans and choose the least expensive. The unit of cost is a single randomfour-kilobyte data page read. Y..

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[Study Notes] optimize MIN() and MAX() [Copied] 2009-8-25 11:58am
MySQL doesn’t optimize certain MIN( ) and MAX( ) queries very well. Here’s anexample: mysql> SELECT MIN(actor_id) FROM sakila.actor WHERE first_name = 'PENELOPE'; Because there’..

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[Work Notes] MySQL query optimizer cost -- Last_query_cost [Original] 2009-8-20 12:55pm
Last_query_cost: The total cost of the last compiled query as computed by the query optimizer. This is useful for comparing the cost of different query plans for the same query. MySQL uses a cost-bas..

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