什么是PostgreSQL的EXPLAIN ANALYZE的MySQL等价物

Question

我想在MySQL中获得类似于PostgreSQL中的EXPLAIN ANALYZE节目的详细查询计划.有同等的吗？

Answer 1

编辑:虽然不是直接等效或详细解释分析这里有一些你可以看到的工具

mysql提供EXPLAIN和procedure analyze()
http://dev.mysql.com/doc/refman/5.0/en/explain.html
http://dev.mysql.com/doc/refman/5.0/en/procedure-analyse html的

Answer 2

我没有在MySQL之前使用过PostgreSQL,EXPLAIN EXTENDED它提供了更多信息,EXPLAIN并且可能会提供您正在寻找的信息.

Answer 3

MySQL 8.0.18 原生引入了EXPLAIN ANALYZE：

MySQL 8.0.18 引入了 EXPLAIN ANALYZE，它运行一个查询并产生 EXPLAIN 输出以及时间和额外的、基于迭代器的关于优化器的期望如何匹配实际执行的信息。对于每个迭代器，提供以下信息：

• 估计执行成本

• 估计的返回行数

• 返回第一行的时间

• 返回所有行的时间（实际成本）

• 迭代器返回的行数

• 循环次数

  EXPLAIN ANALYZE 只能与 SELECT 语句一起使用。

Answer 4

EXPLAIN EXTENDED

MariaDB / MySQL提供了一个称为的东西EXPLAIN EXTENDED。但是，没有替代品EXPLAIN ANALYZE。EXPLAIN EXTENDED不会提供任何时序信息，内部故障也不会那么冗长。

Name: 'EXPLAIN'
Description:
Syntax:
EXPLAIN [explain_type] SELECT select_options

explain_type:
    EXTENDED
  | PARTITIONS

Or:

EXPLAIN tbl_name

The EXPLAIN statement can be used either as a way to obtain information
about how MySQL executes a statement, or as a synonym for DESCRIBE:

o When you precede a SELECT statement with the keyword EXPLAIN, MySQL
  displays information from the optimizer about the query execution
  plan. That is, MySQL explains how it would process the statement,
  including information about how tables are joined and in which order.
  EXPLAIN EXTENDED can be used to obtain additional information.

  For information about using EXPLAIN and EXPLAIN EXTENDED to obtain
  query execution plan information, see
  https://mariadb.com/kb/en/explain/.

o EXPLAIN PARTITIONS is useful only when examining queries involving
  partitioned tables. For details, see
  http://dev.mysql.com/doc/refman/5.5/en/partitioning-info.html.

o EXPLAIN tbl_name is synonymous with DESCRIBE tbl_name or SHOW COLUMNS
  FROM tbl_name. For information about DESCRIBE and SHOW COLUMNS, see
  [HELP DESCRIBE], and [HELP SHOW COLUMNS].

URL: https://mariadb.com/kb/en/explain/

例如，这一点从这个例子所，

EXPLAIN ANALYZE SELECT *
FROM history AS h1
WHERE EXISTS (
  SELECT 1
  FROM history AS h2
  WHERE h1.lead_id = h2.lead_id
  GROUP BY lead_id
  HAVING count(is_first OR NULL) > 1
);

会在PostgreSQL上产生类似的东西，

                                                     QUERY PLAN                                                     
--------------------------------------------------------------------------------------------------------------------
 Seq Scan on history h1  (cost=0.00..82680.50 rows=1100 width=9) (actual time=0.048..0.065 rows=3 loops=1)
   Filter: (SubPlan 1)
   Rows Removed by Filter: 3
   SubPlan 1
     ->  GroupAggregate  (cost=0.00..37.57 rows=1 width=5) (actual time=0.007..0.007 rows=0 loops=6)
           Group Key: h2.lead_id
           Filter: (count((h2.is_first OR NULL::boolean)) > 1)
           Rows Removed by Filter: 0
           ->  Seq Scan on history h2  (cost=0.00..37.50 rows=11 width=5) (actual time=0.003..0.004 rows=2 loops=6)
                 Filter: (h1.lead_id = lead_id)
                 Rows Removed by Filter: 4
 Planning time: 0.149 ms
 Execution time: 0.123 ms
(13 rows)

虽然这相当于MySQL，

+------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
| id   | select_type        | table | type | possible_keys | key  | key_len | ref  | rows | filtered | Extra       |
+------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
|    1 | PRIMARY            | h1    | ALL  | NULL          | NULL | NULL    | NULL |    6 |   100.00 | Using where |
|    2 | DEPENDENT SUBQUERY | h2    | ALL  | NULL          | NULL | NULL    | NULL |    6 |   100.00 | Using where |
+------+--------------------+-------+------+---------------+------+---------+------+------+----------+-------------+
2 rows in set, 2 warnings (0.00 sec)