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...
loop inner join (cost=2.86 rows=4) (actual time=0.039,0.039,0.039..0.039,0.039,0.039 rows=0,0,0 loops=1,1,1) -> Nested loop inner join (cost=1.45 rows=1) (actual time=0.037,0.037,0.037..0.037,0.037,0.037 rows=0,0,0 loops=1,1,1) -> Parallel table scan on customer, with par...
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...
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 ...
We cannot talk about a new feature without an example, so let's look at a simple SELECT query: mysql> EXPLAIN FORMAT=TREE SELECT name, quantity FROM orders JOIN items i ON item_id = i.id WHERE quantity > 1000; -> Nested loop inner join (cost=49828 rows=76470) ...
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mysql> explain select cusno from testa where id=2andname='aaa'; ...
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...
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, ...
With the EXPLAIN output stored in a user variable it can be treated just like any other JSON object in MySQL. This lets you programmatically extract, manipulate, and store data from EXPLAINs directly in the server. As an example we can take this query ...