Mysql “可能的_键”中缺少索引…但仅在某些环境中

我有一个自己运行的软件栈，但也部署到客户场所

有一个特定的查询在我的环境中运行得非常好，但在客户的环境中运行得非常糟糕

我已经使用EXPLAIN确认，我的环境的查询计划器看到有一个很好的索引可用，并使用它。而客户环境中的同一查询在可能的_键下不提供该索引

以下是完整的查询，有些匿名：

选择t0.*， t1.*， t2.*， t3.3价值 从表0到表0 左外连接表1 t1 在t0.id=t1.table0\u id上 左外连接表2 t2 关于t1.id=t2.table1\u id t2.0=0 左外连接表3 t3 在t0.id=t3.table0\u id上 t3.type='whatever' “workcorp”中的t0.business在哪里

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而“2016-11-01 00:00:00”结果是字符集和/或排序规则

我使用此查询来显示每个环境中的字符集：

从信息模式中选择表名、列名、字符集名 其中table\u schema=my\u cool\u数据库 t0、t3中的表_名称 按1说明订购，2 对于奖励积分，我检查了每个环境中的字符排序：

显示t0的完整列； 显示t3的完整列； 在我的环境中：两个表中的所有列都有utf8字符集和utf8\U unicode\U ci排序规则

在客户的环境中：t0完全符合我的环境，而t3是一个独特的雪花；它的列有拉丁字符集和拉丁-瑞典-ci排序

因此，我们看到的是，t3.table0\u id a latin1列上存在的索引不能用于连接到utf8表。因此，该指数在以下方面运行良好：

挑选* 来自表3 其中table0_id=‘随便什么’ 但该指数不能用于：

选择 t0.id， t3.3价值 从t0开始 左外连接t3

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和上描述了类似的症状。

不要从客户的前提中提取太多的查询。在这种情况下，详细信息很重要。我对这里的查询所做的唯一简化是重命名列和表以实现匿名性，并且为了简洁和匿名性，将所选列从每个表扩展到通配符，然后再选择各种特定列。我认为这应该是同等的。我明白细节很重要，但我必须小心，因为客户有严格的安全要求。我想到了这一点——尽管客户和我有相同的索引——也许他们的模式有细微的不同。就像table0一样，id在他们的环境中是一种不同的数据类型、编码或排序规则，在某种意义上，这使得它不适合加入。我会要求他们描述t0和t3。如果你的建议是关于我过滤查询结果的：我同意我省略了一些细节，但我认为我已经包括了所有显示相关佐证或差异的部分。不，不，我的意思是，紧接着就是查询，所以从理论上讲，您可以忽略大量的查询，并像这样认为它似乎不完整-不存在t1或t2表

+----+-------------+-------+------+--------------------------+-----------+---------+------+-------+----------+-------------+
| id | select_type | table | type |      possible_keys       |    key    | key_len | ref  | rows  | filtered |    Extra    |
+----+-------------+-------+------+--------------------------+-----------+---------+------+-------+----------+-------------+
|  1 | SIMPLE      | t3    | ref  | table0_id,type_and_value | table0_id |     108 | func |     2 | 100.00   | Using where |
+----+-------------+-------+------+--------------------------+-----------+---------+------+-------+----------+-------------+

+----+-------------+-------+------+----------------+----------------+---------+-------+----------------+----------+-------------+
| id | select_type | table | type | possible_keys  |       key      | key_len |  ref  | rows           | filtered |    Extra    |
+----+-------------+-------+------+----------------+----------------+---------+-------+----------------+----------+-------------+
|  1 | SIMPLE      | t3    | ref  | type_and_value | type_and_value | 257     | const | (far too many) |   100.00 | Using where |
+----+-------------+-------+------+----------------+----------------+---------+-------+----------------+----------+-------------+

EXPLAIN EXTENDED SELECT t0.*,
       t1.*,
       t2.*,
       t3.value
FROM   table0 t0
LEFT OUTER JOIN table1 t1
             ON t0.id = t1.table0_id
LEFT OUTER JOIN table2 t2
             ON t1.id = t2.table1_id
            AND t2.deleted = 0
LEFT OUTER JOIN table3 t3 FORCE INDEX (table0_id)
             ON t0.id = t3.table0_id
            AND t3.type = 'whatever'
WHERE t0.business IN ('workcorp')
AND '2016-11-01 00:00:00' <= t0.date
AND t0.date < '2016-12-01 00:00:00'
ORDER BY t0.date DESC

+----+-------------+-------+------+---------------+-----------+---------+------+------+-------------+
| id | select_type | table | type | possible_keys |    key    | key_len | ref  | rows |    Extra    |
+----+-------------+-------+------+---------------+-----------+---------+------+------+-------------+
|  1 | SIMPLE      | t3    | ref  | table0_id     | table0_id |     108 | func |    2 | Using where |
+----+-------------+-------+------+---------------+-----------+---------+------+------+-------------+

+----+-------------+-------+------+---------------+------+---------+-------+---------+----------+----------------------------------------------------+
| id | select_type | table | type | possible_keys | key  | key_len | ref   | rows    | filtered | Extra                                              |
+----+-------------+-------+------+---------------+------+---------+-------+---------+----------+----------------------------------------------------+
|  1 | SIMPLE      | t3    | ALL  | NULL          | NULL | NULL    | NULL  | (loads) |   100.00 | Using where; Using join buffer (Block Nested Loop) |
+----+-------------+-------+------+---------------+------+---------+-------+---------+----------+----------------------------------------------------+

+--------+------------+-----------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table  | Non_unique |    Key_name     | Seq_in_index |   Column_name   | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+--------+------------+-----------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| table3 |          0 | PRIMARY         |            1 | id              | A         |       16696 | NULL     | NULL   |      | BTREE      |         |               |
| table3 |          1 | table0_id       |            1 | table0_id       | A         |       16696 | NULL     | NULL   |      | BTREE      |         |               |
| table3 |          1 | type_and_value  |            1 | type            | A         |          14 | NULL     | NULL   |      | BTREE      |         |               |
| table3 |          1 | type_and_value  |            2 | value           | A         |        8348 | NULL     | NULL   |      | BTREE      |         |               |
+--------+------------+-----------------+--------------+-----------------+-----------+-------------+----------+--------+------+------------+---------+---------------+

+--------+------------+-----------------+--------------+-----------------+-----------+-------------------+----------+--------+------+------------+---------+---------------+
| Table  | Non_unique | Key_name        | Seq_in_index | Column_name     | Collation | Cardinality       | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+--------+------------+-----------------+--------------+-----------------+-----------+-------------------+----------+--------+------+------------+---------+---------------+
| table3 |          1 | table0_id       |            1 | table0_id       | A         | (same as PRIMARY) |     NULL | NULL   |      | BTREE      |         |               |
+--------+------------+-----------------+--------------+-----------------+-----------+-------------------+----------+--------+------+------------+---------+---------------+

+----+-------------+--------+------+---------------+-----------+---------+-------+------+----------+-----------------------+
| id | select_type | table  | type | possible_keys |    key    | key_len |  ref  | rows | filtered |         Extra         |
+----+-------------+--------+------+---------------+-----------+---------+-------+------+----------+-----------------------+
|  1 | SIMPLE      | table3 | ref  | table0_id     | table0_id |     108 | const |    1 | 100.00   | Using index condition |
+----+-------------+--------+------+---------------+-----------+---------+-------+------+----------+-----------------------+