case T_ModifyTable: ExplainModifyTarget((ModifyTable *) plan, es); break; case T_NestLoop: case T_MergeJoin: case T_HashJoin: { const char *jointype; switch (((Join *) plan)->jointype) { case JOIN_INNER: jointype = "Inner"; break; case JOIN_LEFT: jointype = "Left"; break;...
In computing, a hash table (hash map) is a data structure used to implement an associative array, a structure that can map keys to values. A hash table uses a hash function to compute anindexinto an array ofbucketsorslots, from which the desired value can be found. 散列(hash)技术:在...
The query plan information generated as openCypher explain output contains tables with one operator per row. The table has the following columns: ID – The numeric ID of this operator in the plan. Out #1 (and Out #2) – The ID(s) of operator(s) that are downstream from this operator....
In computing, a hash table (hash map) is a data structure used to implement an associative array, a structure that can map keys to values. A hash table uses a hash function to compute anindexinto an array ofbucketsorslots, from which the desired value can be found. 散列(hash)技术:在...
<sql_operation type="statement">CREATE TABLE [tempdb].[dbo]. [Q_[TEMP_ID_259]]_ [PARTITION_ID]]]([dist_date] DATE) WITH (DISTRIBUTION = HASH([dist_date]),) </sql_operation> RemoteOnOperation <DestinationCatalog>: The destination catalog.<DestinationSchema>: The destination schema in ...
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, ...
The above tree structure hash node will contain the information of several hash buckets and batches and peak memory uses of SQL statements. The sort node is the main node in the tree structure; it includes information on which algorithm is used to sort the SQL statement. The output will also...
有了这些我们就该优化使用的 SQL,这一般需要为 join、filtering 等操作设计好 index,index 通常小于数据本身的大小,能够放在内存中,避免某些操作进行 disk IO,为必要的地方设置 index 就能加速查询,同时避免 table scan。 MySQL 的 index(包括 primary、unique、index 和 fulltext,对 in memory 的也有 hash),多数...
Operator string structure: In Task M2: Data source: mf_mc_bj.sale_detail_jt/sale_date=2013/region=china # Data source describes the input of the task. TS: mf_mc_bj.sale_detail_jt/sale_date=2013/region=china # TableScanOperator FIL: ISNOTNULL(customer_id) # FilterOperator RS: order:...
Access method – The way in which the data is being accessed, via either a table scan or index access. Join method – The method (e.g., hash, sort-merge, etc.) used to join tables with each other. Join type – The type of join (e.g., outer, anti, semi, etc...