/* Hook for plugins to get control in ExplainOneQuery() */ExplainOneQuery_hook_type ExplainOneQuery_hook = NULL;/* Hook for plugins to get control in explain_get_index_name() */explain_get_index_name_hook_type explain_get_index_name_hook = NULL;/* OR-able flags for ExplainXMLTag()...
ClickHouse是俄罗斯的Yandex于2016年开源的列式存储数据库(DBMS),使用C++语言编写,主要用于在线分析处理查询(OLAP),能够使用SQL查询实时生成分析数据报告。 OLAP(On-Line Analytical Processing)翻译为联机分析处理,专注于分析处理,从对数据库操作来看,OLAP是对数据的查询; OLTP(on-line transaction processing)翻译为联机...
You can zoom in or out, choose detail levels, export it to an image file, or print it using the toolbar buttons. The relative cost is indicated by node color and If you click the output results card, you can see all the query execution details on the right. SQL Query Results with ...
the MySQL optimizer considers many techniques to efficiently performthe lookups involved in an SQL query. A query on a huge table can be performedwithout reading all the rows; a join involving several tables can be performedwithout comparing every combination of rows. The set of operations...
EXPLAIN 语句用于解释 query 或 INSERT 语句的执行逻辑,也用于优化 query 语句的查询计划。 1、语法 EXPLAIN [([ExplainDetail[, ExplainDetail]*]) | PLAN FOR] <query_statement_or_insert_statement_or_statement_set> statement_set: EXECUTE STATEMENT SET BEGIN insert_statement; ... insert_statement; END...
In the information age, the most obvious thing we can feel is the explosion of dense data, and people are accumulating more and more data. These complex data appear together, and many traditional data recording, query, and summary tools cannot meet people's needs. More effective processing of...
If a large number of DDL statements are executed on the partitioned parent table, the processing speed of SE is slow and the latency is high. As a result, data write and read are slow. In this case, you can optimize the frequency of executing DDL statements. Lock query cost: the ...
Each row contains the values summarized in Table 10.1, “EXPLAIN Output Columns”, and described in more detail following the table. Column names are shown in the table's first column; the second column provides the equivalent property name shown in the output when FORMAT=JSON is used. ...
Each row contains the values summarized in Table 10.1, “EXPLAIN Output Columns”, and described in more detail following the table. Column names are shown in the table's first column; the second column provides the equivalent property name shown in the output when FORMAT=JSON is used. ...
When this operation completes then the resultant row source is passed up to the next level of the query for processing. In this case it is the SELECT STATEMENT which is the top of the query. [CHOOSE] is an indication of the optimizer_goal for the query. This DOES NOT necessarily ...