table_ident 语义组用于解析 ident 或ident.ident,详见 MySQL 源码|41 - 语法解析(V2):标识符 IDENT;opt_describe_column 语义组用于解析需要描述的字段名或通配符,详见下文。 语义组:describe_command describe_command 语义组用于解析 DESCRIBE、EXPLAIN 和DESC 关键字。 标准语法:{EXPLAIN | DESCRIBE | DESC} ...
distinct: 一旦mysql找到了与行相联合匹配的行,就不再搜索了 mysql> explain select distinct name from film left join film_actor on =+---+---+---+---+---+---+---+---+---+---+ | id | select_type | table | type | possible_keys | key | key_len | ref | ro...
describe_command语义组用于解析DESCRIBE、EXPLAIN和DESC关键字,详见下文; table_ident语义组用于解析ident或ident.ident,详见MySQL 源码|41 - 语法解析(V2):标识符 IDENT; opt_describe_column语义组用于解析需要描述的字段名或通配符,详见下文。 语义组:describe_command describe_command语义组用于解析DESCRIBE、EXPLAIN和...
I have a JOIN query that joining 5 tables. I have added indexes for all the fields that are using in the where clause. When I executed the EXPLAIN command for MySql, I got the first line like below. id : 1 select_type : SIMPLE ...
mysql>CREATEFUNCTION`cleanup`()RETURNSchar(50) CHARSET utf8mb4 -> DETERMINISTIC ->BEGIN ->deletefromtest.t1; ->RETURN'OK'; ->END$$ Query OK, 0rowsaffected (0.00 sec) mysql> 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
mysql_parse mysql_execute_command Sql_cmd_dml::execute Sql_cmd_dml::execute_inner explain_query ExplainIterator PrintQueryPlan ExplainAccessPath TimingIterator<RealIterator>::TimingString TimingIterator<RealIterator>::TimingString 函数,会基于执行阶段的统计打印以下信息: ...
可以看到,会话1的执行计划实际上是个全表扫描,而非idx_c上的索引扫描。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 # Session2MySQL[sbtest]>explainforconnection20264939;+---+---+---
对于Command字段,对应的状态如下: sleep:正在等待客户端发送新的请求 query:正在执行查询或者正在将结果发送给客户端 locked:在MySQL服务层,线程正在等待表锁 analyzing and statistics:线程正在收集存储引擎的统计信息,并生成查询的执行计划 copying to tmp table:线程正在执行查询,并且将其结果集都复制到一个临时表中 ...
The EXPLAIN command provides information about how MySQL executes queries. EXPLAIN can work with SELECT, DELETE, INSERT, REPLACE, and UPDATE statements. We'll first analyze the original query, then attempt to optimize the query and look into the optimiz
– you do not expect to get different information in different “formats” of the same command and I filed a bug for hash join already. 0 Pavel Katiushyn 5 years ago Thank you for the post. The overhead is really worrying. I hope it adds equally to each step it measures...