A join is implemented using full partition-wise join if the partition row source appears before the join row source in theEXPLAINPLANoutput. Full partition-wise joins are possible only if both joined tables are equi-partitioned on their respective join columns. Examples of execution plans for sev...
Explain examples The following is a basic example of openCypherexplainoutput. The query is a single-node lookup in the air routes dataset for a node with the airport codeATLthat invokesexplainusing the details mode: ## sample queryaws neptune-graph execute-query \ --region <region> \ --gra...
Consumer processes typically perform a sorting function. If there is no requirement for the data to be sorted then the consumer slaves are not produced and we end up with the number of slaves used matching the degree of parallelism as opposed to being 2x the degree. Parallel Terms Examples of...
The following table describes the categories of hash joins. Category Description Hash Left Join When multiple tables are joined, all rows in the left table that meet the join conditions are returned and then matched against the right table. If no data is matched, null is returned. Hash ...
With the help ofEXPLAIN, you can see where you should add indexes to tables so that thestatement executes faster by using indexes to find rows. You can also useEXPLAIN to check whether the optimizer joins the tables in an optimal order. Togive a hint to the optimizer to use a join orde...
Example 2:Retrieve the information returned in Example 1. Assume that a statement table exists, so also retrieve the estimated cost of processing the query. Use the following query, which joins the plan table and the statement table. SELECT * FROM PLAN_TABLE A, DSN_STATEMNT_TABLE B WHERE ...
This join type is like ref, but with the addition that MySQL does an extra search for rows that contain NULL values. This join type optimization is used most often in resolving subqueries. In the following examples, MySQL can use a ref_or_null join to process ref_table: SELECT * FROM...
For additional examples of using EXPLAIN, see the following documents: Indexes Joins Subqueries Aggregation Views Partitions Understand EXPLAIN output The following describes the output of the EXPLAIN statement above: id describes the name of an operator, or sub-task that is required to execute the ...
Applies only in NDB Cluster, when pushed-down joins are enabled. See the description of the ndb_join_pushdown server system variable for more information and examples. const row not found (JSON property: const_row_not_found) For a query such as SELECT ... FROM tbl_name, the table ...
How does one device (such as a Wi-Fi router) know when another abruptly joins or leaves the network? How can it maintain the performance of the network when lots of people try to join at the same time? What if all the network devices are using slightly different versions of Wi-Fi or...