unionM,N: The row refers to the union of the rows with id values of M and N. derivedN: The row refers to the derived table result for the row with an id value of N. A derived table may result, for example, from a subquery in the FROM clause. subqueryN: The row refers to the...
DFEWCCAlgo – Explain operator for invocations of the Weakly Connected Components algorithm, which finds the weakly-connected components in a directed graph. SolutionInjection – Appears before everything else in the explain output, with a value of one in the Units Out column. However, it serves...
In most cases, broadcast join is used to join small tables with large tables. When an SQL statement is delivered, the QO compares the costs of redistribution and broadcast, and then generates an execution plan based on the algorithm. Optimization suggestion: If the table that you want to ...
Analgorithmis a list of instructions to take in some data and spit out some other data. For example, subtracting someone’s age from the current year to get the year they were born is an algorithm: regardless of how old someone is, if you follow those steps you’ll always get the year...
Merge JoinmjoinAlso used for inner joins and outer joins (for join tables that are both distributed and sorted on the joining columns). Typically the fastest Amazon Redshift join algorithm, not including other cost considerations. AGGREGATION:Operators and steps used for queries that involve aggrega...
In this example only the rows from the sales tables need to be sorted (ID 5), the rows from the products table are already sorted on the join column coming from the primary key index access (ID 4). Figure 19: Example plan output using SORT MERGE JOIN Beginning with Oracle Database ...
Briefly explain the purpose of the loop, or iteration, structure. Then provide an original example algorithm with the loop structure. Give two reasons describing why is it often a good idea to separate different tasks in your program into separate, individual methods? What is the te...
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...
Sort Selected rows were sorted using a sort algorithm. Union Merge The results of multiple subselects were merged or combined into a single result. Subquery Merge The results of multiple subselects were merged or combined into a single result. Bitmap Merge Multiple bitmaps were merged or combined...
Use theDEBUGoption to generate a ZIP file containing files with information about the query and the database objects referenced in the query. For example: EXPLAINANALYZE(DEBUG)SELECTcity,AVG(revenue)FROMridesGROUPBYcity; info --- Statement diagnostics bundle generated. Download using the SQL shell ...