11. Aggregation related operations
This type of operation is related to the SQL statement containing the aggregation operation.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
The data is grouped by the hash algorithm, compared to the previous sorting grouping (SORTGROUP BY) algorithm, hash algorithm is more efficient, this operation first appeared in Oracle 10.2.0 version.
--Note:
1) The premise of this operation appearing in the execution plan is that the parameter "_gby_hash_aggregation_enabled" is set totrue, in Oracle version 11.2.0, this parameter defaults to true.
This operation is specifically shown in node 1 in Figure 11-1
