Index Operations === Query execution: # of statement index ops: 23191 # of unique statement index ops: 5960 Duplication ratio: 3.89 # of terms materialized: 0 這些報告: 索引查閱的總數。 已執行的唯一索引查詢數目。 索引查詢總數與唯一索引查詢數目的比率。較低的比率指示較少的冗餘。 從字詞字典具體...
unionM,N: The row refers to the union of the rows with id values of M and N. derivedN: The row refers to the derived table result for the row with an id value of N. A derived table may result, for example, from a subquery in the FROM clause. subqueryN: The row refers to the...
Use the EXPLAIN statement to display the execution plan for the query. EXPLAIN can be used with any SELECT, INSERT, UPDATE, DELETE, VALUES, EXECUTE, DECLARE, or CREATE TABLE AS statement.EXPLAIN displays the execution plan for the query, allowing you to understand how PostgreSQL: executes a ...
Parallel execution, such as the distribution method of join inputs TheEXPLAINPLANresults let you determine whether the optimizer selects a particular execution plan (for example, nested loops join). It also helps you to understand the optimizer decisions (for example, why the optimizer chose a ne...
The EXPLAINstatement provides information about the execution plan for a SELECT statement. EXPLAIN returnsa row of information for each table used in the SELECT statement. It lists thetables in the output in the order that MySQL would read them while processingthe statement. MySQL resolves all joi...
FirstMatch execution strategy (首次匹配) FirstMatch是一种最原始的半连接执行方式,简单来说就是说先取一条外层查询的中的记录,然后到子查询的表中寻找符合匹配条件的记录,如果能找到一条,则将该外层查询的记录放入最终的结果集并且停止查找更多匹配的记录,如果找不到则把该外层查询的记录丢弃掉;然后再开始取下一...
ORDER BY Students.StudentID, Enrollments.CourseName LIMIT 10; NOTICE: INFO: query execution complete; now resetting client_min_messages QUERY PLAN --- ___ DSEF for PostgreSQL (DiffStats
AfterSolutionInjectionat the top-level is theDFESubqueryoperator.DFESubqueryencapsulates the parts of the query execution plan that are pushed to the DFE engine (for openCypher queries, the entire query plan is executed by the DFE). All the operators in the query plan are nested insidesubQuery1...
EXPLAIN is used to obtain a query execution plan (that is, an explanation of how MySQL would execute a query). 简单翻译一下,就是explain用于获取查询执行计划(即MySQL是如何执行一个查询的)。 工作中,我们会遇到慢查询,这个时候我们就可以在select语句之前增加explain关键字,模拟MySQL优化器执行SQL语句,从而...
order by max(B.sal), avg(B.sal) desc; Execution Plan #3 (Parallel) OBJECT_NAME OBJECT_NODE OTHER --- --- --- SELECT STATEMENT Cost = ?? SORT ORDER BY :Q58002 **[6]** SORT GROUP BY :Q58001 **[5]** NESTED LOOPS JOIN :Q58000 **...