MySQL因数据类型转换导致执行计划使用低效索引的案例分析

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查看表的索引情况
 
mysql> show keys from who_goods;
+-----------+------------+-------------------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table     | Non_unique | Key_name                | Seq_in_index | Column_name       | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+-----------+------------+-------------------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| who_goods |          0 | PRIMARY                 |            1 | goods_id          | A         |       68442 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_gid    |            1 | is_delete         | A         |           4 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_gid    |            2 | is_on_sale        | A         |           8 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_gid    |            3 | cat_id            | A         |         551 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_gid    |            4 | goods_id          | A         |       68442 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_update |            1 | is_delete         | A         |           4 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_update |            2 | is_on_sale        | A         |           8 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_update |            3 | cat_id            | A         |         551 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_del_sale_cat_update |            4 | last_update       | A         |       68442 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | goods_sn                |            1 | goods_sn          | A         |        4888 |        7 | NULL   |      | BTREE      |         |               |
| who_goods |          1 | add_time                |            1 | add_time          | A         |       68442 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | last_update             |            1 | last_update       | A         |       68442 |     NULL | NULL   |      | BTREE      |         |               |
| who_goods |          1 | idx_provider_code       |            1 | provider_code     | A         |         786 |        3 | NULL   |      | BTREE      |         |               |
| who_goods |          1 | inx_code                |            1 | goods_search_code | A         |        1801 |     NULL | NULL   |      | BTREE      |         |               |
+-----------+------------+-------------------------+--------------+-------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
14 rows in set (0.00 sec)
 
           id: 1
  select_type: SIMPLE
        table: who_goods
         type: range
possible_keys: PRIMARY,idx_del_sale_cat_gid,idx_del_sale_cat_update
          key: PRIMARY
      key_len: 3
          ref: NULL
         rows: 14
        Extra: Using where
1 row in set (0.00 sec)
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