mysql大表更新sql的优化策略_MySQL
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问题sql背景：项目有6个表的要根据pid字段要写入对应的brand_id字段。但是这个其中有两个表是千万级别的。我的worker运行之后，线上的mysql主从同步立刻延迟了！运行了一个多小时之后，居然延迟到了40分钟，而且只更新了十几万行数据。问题sql如下：
<!-- 根据商品id更新品牌id --> <update id="updateBrandIdByPid" parameterClass="com.jd.chat.worker.domain.param.UpdateBrandIdParam"> UPDATE $tableName$ SET brand_id = #newBrandId# WHERE pid = #pid# AND brand_id = 0 </update>
同事给我的建议的根据id字段进行sql代码层次的纵向分表。每次更新1000行的数据，这样mysql引擎就不用每次在扫全表了，数据库压力是之前的万分之一。而且id作为主键，是有索引的有索引，有索引能大大优化查询性能，优化后的sql如下：
<!-- 根据商品id更新品牌id --> <update id="updateBrandIdByPid" parameterClass="com.jd.chat.worker.domain.param.UpdateBrandIdParam"> UPDATE $tableName$ SET brand_id = #newBrandId# WHERE pid = #pid# AND brand_id = 0 AND id BETWEEN #startNum# AND #endNum# </update>
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