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MYSQL5.7:OPTIMIZER Contradict Explain
Posted by: yijie fu
Date: September 07, 2022 05:02AM

MYSQL5.7:OPTIMIZER Contradict Explain
example1:
Index:ALTER TABLE t_app_recommended_info ADD INDEX idx_uid_create_time_type (uid,create_time,type);
SQL:select * from t_app_recommended_info where uid = 1252057754179211264 and create_time >'2022-09-01 00:00:00' and type =1 and params like '%"couponId":12582268875%' and params like '%"hmsr":"saomaqudao"%';
explain:key-len=12

OPTIMIZER_TRACE:refine_plan: "pushed_index_condition": "((`t_app_recommended_info`.`type` = 1) and (`t_app_recommended_info`.`uid` = 1252057754179211264) and (`t_app_recommended_info`.`create_time` > '2022-09-01 00:00:00'))",
example2:
Index:ALTER TABLE t_app_recommended_info ADD INDEX idx_uid_type_createtime (uid,type,create_time);
SQL:select * from t_app_recommended_info where uid = 1252057754179211264 and create_time >'2022-09-01 00:00:00' and type =1 and params like '%"couponId":12582268875%' and params like '%"hmsr":"saomaqudao"%';
explain:key-len=16

OPTIMIZER_TRACE:refine_plan: "pushed_index_condition": "((`t_app_recommended_info`.`type` = 1) and (`t_app_recommended_info`.`uid` = 1252057754179211264) and (`t_app_recommended_info`.`create_time` > '2022-09-01 00:00:00'))",
example1 compair example2 [explain key-len] find type(4byte)not used,but OPTIMIZER_TRACE:refine_plan: find user index' type,help.

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