Oracle SQL execution plan operations (10) - operations related to aggregation and analysis functions

​​​​11.  Aggregation related operations

This type of operation is related to SQL statements that contain aggregate operations. Depending on the specific SQL statement and other related factors, the following operations may appear in the execution plan of the relevant SQL statement.

1）HASH GROUP BY

Data is grouped by the hash algorithm, which is more efficient than the previous SORT GROUP BY algorithm. This operation first appeared in Oracle version 10.2.0.

--Note:

      1) The prerequisite for this operation to appear in the execution plan is that the parameter "_gby_hash_aggregation_enabled" is set to true. In Oracle version 11.2.0, this parameter defaults to true.

This operation is specifically shown in node 1 in Figure 11-1