The query plan information generated as openCypher explain output contains tables with one operator per row. The table has the following columns: ID – The numeric ID of this operator in the plan. Out #1 (and Out #2) – The ID(s) of operator(s) that are downstream from this operator...
本文将致力于帮助大家充分理解explain所返回的各项参数,从而使大家快速掌握explain用法技巧。如果你在看其他教程或视频后仍觉得云里雾里。那么请通读本文。 用法 explain的用法相当简洁,直接在sql语句前加上EXPLAIN 即可,例如: 本语句将返回: 每行将得到id,select_type,table,type,......
For example, if rows is 1000 and filtered is 50.00 (50%), the number of rows to be joined with the following table is 1000 × 50% = 500. ❝ 译文:是一个多少行会被表条件过滤的百分比估计值,一般与rows列结合着看,filtered × rows就是被表条件过滤掉的行数。 = explain select title ...
SHOW TABLE STATUS\G *** 1. row *** Name: pq_test Engine: InnoDB Version: 10 Row_format: Dynamic Rows: 20064988 Avg_row_length: 1898 Data_length: 38085328896 Max_data_length: 0 Index_length: 0 Data_free: 4194304 Auto_increment: 21495809 Create_time: 2019-07-30 01:35:27 Update...
Mysql性能分析(重点Explain)--重要(六) Explain: select_type:SIMPLE 简单类型select_type:PRIMARY 最外层查询类型,SUBQUERY子查询类型<derived2> 的这个2指的是ID为2 的t3这个表衍生出来的虚表。 table: 显示这行数据是关于哪张表的 type:、 因为我们前面创建的索引是create index col1_col2_col3 t1(col1智...
es->rtable_names); es->printed_subplans = NULL; /* * Sometimes we mark a Gather node as "invisible", which means that it's * not displayed in EXPLAIN output. The purpose of this is to allow * running regression tests with force_parallel_mode=regress to get the * same results as ...
官网地址:http://dev.mysql.com/doc/refman/5.6/en/explain-output.html EXPLAIN语句返回MYSLQ的执行计划,通过他返回的信息,我们能了解到MYSQL优化器是如何执行SQL语句的,通过分析他能帮助你提供优化的思路。 语法 MYSQL 5.6.3以前只能EXPLAIN SELECT; MYSQL5.6.3以后就可以EXPLAIN SELECT,UPDATE,DELETE ...
In other words, an algorithm is the core of a flowchart. Actually, in the field of computer programming, there are many differences between algorithm and flowchart regarding various aspects, such as the accuracy, the way they display, and the way people feel about them. Below is a table ...
- The teacher explained the grammar rules in detail to the students. Explain语句 Explain语句 序⾔ Explain 语句提供了mysql如何执⾏语句的信息,包括 select , delete , insert , replace , update Explain输出的列 Column id select_type table partitions type possible_keys key key_len ref rows ...
Query statement to explain. The query can be a SELECT, INSERT, CREATE TABLE AS, UPDATE, or DELETE statement. Usage notes EXPLAIN performance is sometimes influenced by the time it takes to create temporary tables. For example, a query that uses the common subexpression optimization requires tempo...