生产环境MySQL索引时效的排查过程

来源：jb51　　时间：2022/4/11 8:45:04　　对本文有异议

早上收到开发同学求助，有个SQL查询耗时特别长，看了执行计划发现没有走索引，但是不知道原因在哪里，我们一起来分析一下。

mysql>explain SELECT
	* 
FROM
	artisan_income 
WHERE
	parent_id IN (
		222645481,
		222583953,
		222181775,
		222180931,
		222081126,
		221678753,
		221616102,
		221591783,
		221219312,
		221195482,
		221118672,
		220763129,
		220654289,
		220633930,
		220323633,
		220227641,
		219825564,
		219720338,
		219321345,
	219291958 
	) \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: artisan_income
   partitions: 
         type: ALL
possible_keys: idx_parent_id
          key: 
      key_len: 
          ref: 
         rows: 20711352
     filtered: 100
        Extra: Using where

确实是全表扫描，带着疑问我们把生产环境数据同步到测试库，方便测试，然后在测试环境进行查询。

mysql>explain SELECT
	* 
FROM
	artisan_income 
WHERE
	parent_id IN (
		222645481,
		222583953,
		222181775,
		222180931,
		222081126,
		221678753,
		221616102,
		221591783,
		221219312,
		221195482,
		221118672,
		220763129,
		220654289,
		220633930,
		220323633,
		220227641,
		219825564,
		219720338,
		219321345,
	219291958 
	) \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: artisan_income
   partitions: 
         type: range
possible_keys: idx_parent_id
          key: idx_parent_id
      key_len: 5
          ref: 
         rows: 1870780
     filtered: 100
        Extra: Using index condition

发现在测试环境就用到了parent_id字段的索引，生产库和测试库同样都是5.7的版本，数据也几乎一样，但是执行计划不一样，第一时间想到了统计信息的问题，于是进行analyze table

analyze table artisan_income;

然后查看执行计划：

mysql>explain SELECT
	* 
FROM
	artisan_income 
WHERE
	parent_id IN (
		222645481,
		222583953,
		222181775,
		222180931,
		222081126,
		221678753,
		221616102,
		221591783,
		221219312,
		221195482,
		221118672,
		220763129,
		220654289,
		220633930,
		220323633,
		220227641,
		219825564,
		219720338,
		219321345,
	219291958 
	) \G
*************************** 1. row ***************************
           id: 1
  select_type: SIMPLE
        table: artisan_income
   partitions: 
         type: range
possible_keys: idx_parent_id
          key: idx_parent_id
      key_len: 5
          ref: 
         rows: 1901880
     filtered: 100
        Extra: Using index condition

发现执行计划已经恢复正常。

mysql>SELECT
	* 
FROM
	artisan_income 
WHERE
	parent_id IN (
		222645481,
		222583953,
		222181775,
		222180931,
		222081126,
		221678753,
		221616102,
		221591783,
		221219312,
		221195482,
		221118672,
		220763129,
		220654289,
		220633930,
		220323633,
		220227641,
		219825564,
		219720338,
		219321345,
	219291958 
	) \G
返回行数：[0]，耗时：2 ms.