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【mysql】关于Index Condition Pushdown特性

发布时间:2015-11-11 23:00:04
关于ICPIndex Condition Pushdown (ICP) is an optimization for the case where MySQL retrieves rows from a table using an index. Without ICP, the ...

【mysql】关于Index Condition Pushdown特性

关于ICP

Index Condition Pushdown (ICP) is an optimization for the case where MySQL retrieves rows from a table using an index. Without ICP, the storage engine traverses the index to locate rows in the base table and returns them to the MySQL server which evaluates the WHEREcondition for the rows. With ICP enabled, and if parts of the WHERE condition can be evaluated by using only fields from the index, the MySQL server pushes this part of the WHERE condition down to the storage engine. The storage engine then evaluates the pushed index condition by using the index entry and only if this is satisfied is the row read from the table. ICP can reduce the number of times the storage engine must access the base table and the number of times the MySQL server must access the storage engine.

也就说:利用索引来过滤一部分where条件

测试

导入数据库

wget https://launchpad.net/test-db/employees-db-1/1.0.6/+download/employees_db-full-1.0.6.tar.bz2tar jxf employees_db-full-1.0.6.tar.bz2cd employees_dbmysql -uroot -p < employees.sql

原标题:【mysql】关于Index Condition Pushdown特性

关键词:MYSQL

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