Deleting unused projections
yamakawa
Vertica Customer ✭
Dear all
Thank you for your interest.
Currently, there are projections that are being notified as candidates for deletion by ManagementConsole.
They are TBL_pk_b0 and TBL_pk_b1 in the following table.
The following projections exist in the table.
| projection_name | anchor_table_name | create_type | is_super_projection | is_key_constraint_projection | segment_expression |
|---|---|---|---|---|---|
| TBL_pk_b0 | TBL1 | DELAYED CREATION | f | t | hash(TBL1.COL1, TBL1.COL2) |
| TBL_pk_b1 | TBL1 | DELAYED CREATION | f | t | hash(TBL1.COL1, TBL1.COL2) |
| TBL_DBD_212_seg_b0 | TBL1 | DESIGHER | t | f | hash(TBL1.COL1, TBL1.COL2) |
| TBL_DBD_212_seg_b1 | TBL1 | DESIGHER | t | f | hash(TBL1.COL1, TBL1.COL2) |
| TBL_DBD_2_seg_b0 | TBL1 | DESIGHER | f | f | hash(TBL1.COL2) |
| TBL_DBD_2_seg_b1 | TBL1 | DESIGHER | f | f | hash(TBL1.COL2) |
Also, if you check v_catalog.projection_usage, there is no usage history for the projection in question.
Deleting it doesn't seem to be a problem.
I'd like to know if it's OK for the is_key_constraint_projection=true projection to no longer exist.
That's all, I'm looking forward to your answer.
Best Answer
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Vertica_Curtis
Employee
These types of projections exist because they are basis for enabled key constraints on the table. So, you've got a primary key constraint on the table, and it was set as "TRUE" for purposes of enforcing uniqueness, and this projection enforces the uniqueness of a PK constraint on that table. So, it's likely you might not be able to just drop this projection without also dropping the unique PK constraint on the table.
0
Answers
Dear Vertica_Curtis
Thank you for your answer.
I'm glad to know the information before I run the
dropcommand.Even if the projection is not being used, it is necessary for PK constraints, so I will leave the projection as it is.