5.137 DBA_JOINGROUPS
DBA_JOINGROUPS
describes join groups in the database. A join group is a user-created object that consists of two or more columns that can be meaningfully joined. The maximum number of columns that can be included in a join group is 255.
Related View
In certain queries, join groups enable the database to eliminate the performance overhead of decompressing and hashing column values. Join groups require an In-Memory column store (IM column store).
USER_JOINGROUPS
describes join groups belonging to the user. This view does not display the JOINGROUP_OWNER
column.
Column | Datatype | NULL | Description |
---|---|---|---|
|
|
|
Join group owner. This is the user that created the join group. |
|
|
|
This is the user specified name of the join group. The join group name is specified when the join group is created as part of the |
|
|
|
Table owner |
|
|
|
Table name |
|
|
|
Column name |
|
|
|
Possible values:
|
|
|
|
The memory address of the global dictionary. Ideally, all the columns in one join group should have the same global dictionary address (that is, they share the same global structure). This might not always be the case (for example, a column might be added to a join group after it was populated into memory - in which case its |
See Also:
-
Oracle Database In-Memory Guide for an introduction to join groups
-
Oracle Database SQL Language Reference for information about creating a join group using the
CREATE INMEMORY JOIN GROUP
statement