没有索引也可以快速查询
仓储系统有张表，4000万数据，按照创建时间清理。创建时间上没有索引，不过数据是按照创建时间一条条的insert的。这样就写了个脚本按照id升序每次处理2000个，然后删除掉。这样只要扫描到的数据满足时间条件，速度和有索引是一样的。一旦处理到不满足时间条件
仓储系统有张表，4000万数据，按照创建时间清理。创建时间上没有索引，不过数据是按照创建时间一条条的insert的。这样就写了个脚本按照id升序每次处理2000个，然后删除掉。这样只要扫描到的数据满足时间条件，速度和有索引是一样的。一旦处理到不满足时间条件的数据，整个sql就会超时了，这样就不再处理，第二天再处理了满足条件的。没有索引一样快。
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