DFESubquery encapsulates the parts of the query execution plan that are pushed to the DFE engine (for openCypher queries, the entire query plan is executed by the DFE). All the operators in the query plan are nested inside subQuery1 that is referenced by DFESubquery. All the operators ...
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...
Hash Intersect [Distinct]hjoinUsed for INTERSECT queries. Can operate from disk based on virtue of fact that input hash can be disk-based. Append [All |Distinct]saveAppend used with Subquery Scan to implement UNION and UNION ALL queries. Can operate from disk based on virtue of "save". ...
Figure 7.7 A Visual Explain Example The next visual explain diagram shows the visual representation of a query that contains a hash join. Prior to MySQL Workbench 8.0.22, a hash join was represented by ablock nested loopdiamond for queries executed by MySQL 8.0.19 (or earlier). ...
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) ...
ExplainPropertyListNested(keyname, result, es); } ExplainCloseGroup(keysetname, keysetname, false, es); if (sortnode && es->format == EXPLAIN_FORMAT_TEXT) es->indent--; ExplainCloseGroup("Grouping Set", NULL, true, es);}/* * Show the grouping keys for a Group node. */static voi...
recursive calls are basically SQL performed on behalf of your SQL. So, if you had to parse the query, for example, you might have had to run some other queries to get data dictionary information. These would be recursive calls. Space management, security checks, calling PL/SQL from SQL—...
The performance of the EXPLAIN statement is mostly affected by the factor of the time taken for the creation of the temporary tables. While executing query statements that include the subexpression or nested queries, there might be a necessity of creation of the internal temporary tables by the ...
Since EXPLAIN ANALYZE actually runs the query, use it cautiously with resource-intensive queries, especially in production environments. Alternatively, you can use EXPLAIN alone to avoid running the query while still viewing the execution plan. ...
Index Scan:Faster for selective queries, leveraging an index. Nested Loop, Hash Join, Merge Join:Join types that PostgreSQL chooses based on data and index availability. Practical Applications of EXPLAIN Query Optimization:Identify which parts of a query are causing slow performance. ...