上边的 GROUP BY 的执行计划的 Extra 列不仅仅包含 Using temporary 提示,还包含 Using filesort 提示,可是查询语句中明明没有写 ORDER BY 子句,这是因为 MySQL 会在包含 GROUP BY 子句的查询中默认添加上 ORDER BY 子句。 如果不想为包含 GROUP BY 子句的查询进行排序,需要显式的写上
rollup函数使用sort耗时长,总耗时达到50s(即17号-20号算子的总耗时),(并行度32的情况下),20号算子Vector sort达24s,19号算子Vector Sore Aggregate达9s,18号算子做重分布达10s,17号算子hashagg达到8s。因此需要考虑对rollup类的分析函数考虑使用其它方式进行优化,比如用hashagg替代sortagg,避免大数据量排序性能降低。
To use the information that the openCypher explain feature provides, you need to understand some details about how the DFE query engine works (DFE being the engine that Neptune uses to process openCypher queries). The DFE engine translates every query into a pipeline of operators. Starting fro...
Using sort_union(...), Using union(...), Using intersect(...) (JSON property: message) These indicate the particular algorithm showing how index scans are merged for the index_merge join type. See Section 10.2.1.3, “Index Merge Optimization”. Using temporary (JSON property: using_tem...
Using sort_union(...), Using union(...), Using intersect(...) (JSON property: message) These indicate the particular algorithm showing how index scans are merged for the index_merge join type. See Section 10.2.1.3, “Index Merge Optimization”. Using temporary (JSON property: using_tem...
For example, if the Final Select ICON has a unique ICON number of 12, then all records with a unique ICON number of 12 contain information about the Final Select ICON. The record immediately following the Final Select record is the record that tells the user how many ICONs (called child ...
BaseStream with timeout Async/Await - How to stop the insanity Asynchronous FTP with the new Async methods Attempted to read or write protected memory attempted to read or write protected memory!! Attempted to read or write protected memory. This is often an indication that other memory is ...
tuned such that localized peaks can be sustained in the absence of continuing input. Neural populations exhibiting self-sustained activation of this sort have been identified in a range of different cortical areas, including the lateral prefrontal cortex, inferior temporal cortex, parietal cortex, ...
Using sort_union(...), Using union(...), Usingintersect(...) (JSON property: message) Theseindicate how index scans are merged for the index_merge jointype. See Section 9.2.1.4, “Index MergeOptimization”. Using temporary (JSON property: using_temporary_table) ...
Default: 0. passes— Specifies how many passes to run. If set to -1, runs all the passes. Default: -1. Example: EXPLAIN QUERY TREE SELECT id, value FROM test_table;QUERY id: 0 PROJECTION COLUMNS id UInt64 value String PROJECTION LIST id: 1, nodes: 2 COLUMN id: 2, column_name: ...