All the operators in the query plan are nested inside subQuery1 that is referenced by DFESubquery. All the operators that are pushed down to the DFE engine have names that start with a DFE prefix. As mentioned above, the whole openCypher query plan is executed by the DFE, so as a ...
使用了连接缓存:Block Nested Loop,连接算法是块嵌套循环连接;Batched Key Access,连接算法是批量索引连接 Impossible where 该WHERE子句始终为false,不能选择任何行。 Select tables optimized away 在没有GROUP BY子句的情况下,基于索引优化MIN/MAX操作,或者对于MyISAM存储引擎优化COUNT(*)操作,不必等到执行阶段再进行...
(cost=103382.56 rows=1029632) -> Nested loop inner join (cost=409.36 rows=4022) -> Filter: (nation.N_NAME = 'IRAN') (cost=2.29 rows=3) -> Table scan on nation (cost=2.29 rows=25) -> Parallel index lookup on supplier using SUPPLIER_FK1 (S_NATIONKEY=nation.N_NATIONKEY), with ...
Query OK,0rows affectedRecords:0Duplicates:0Warnings:0mysql> insert into testa values(2,2,'aaa'); Query OK,1row affected# 下面possible_keys可能会用到的索引有主键和我建的索引,但是key实际用到的是主键,主键长度是4,ref用的列的名字(或单词“const”,此处用的是常量const,速度快,rows扫描的只有1行...
For example, if a query shows high buffer usage, it may indicate that the query is performing a lot of disk I/O, which could be a performance bottleneck, especially if the data is not cached in memory. auto_explain.log_timing Purpose: Similar to log_analyze, this set...
The following example returns the query plan for the same query with verbose output: explain verboseselecteventid, eventname,event.venueid, venuenamefromevent, venuewhereevent.venueid = venue.venueid; QUERY PLAN ---{HASHJOIN:startup_cost2.52:total_cost58653620.93:plan_rows8712:plan_width43:best...
The performance of the EXPLAIN statement is mostly affected by the factor of the time taken for the creation of the temporary tables. While executing query statements that include the subexpression or nested queries, there might be a necessity of creation of the internal temporary tables by the ...
recursive calls are basically SQL performed on behalf of your SQL. So, if you had to parse the query, for example, you might have had to run some other queries to get data dictionary information. These would be recursive calls. Space management, security checks, calling PL/SQL from SQL—...
Explain output is limited by the maximum Nested Depth for BSON Documents, which is 100 levels of nesting. Explain output that exceeds the limit is truncated. For details on the output, see Explain Results. Examples queryPlanner Mode The following explain command runs in "queryPlanner" verbosity ...
For example, if a hash aggregate operator is used in the first step of a query plan, full data of downstream operators is required to create a hash table for an aggregate operation. For common queries with filter conditions, data is calculated and returned in real time. In this scenario, ...