Note
This parameter was introduced in OceanBase Database V3.2.3 BP10.
Description
optimizer_index_cost_adj specifies the proportion of statistics cost in the index scanning cost calculated by the optimizer.
Attributes
| Attribute | Description |
|---|---|
| Type | Integer |
| Default value | 0 |
| Value range | [0, 100]
NoteWe recommend that you set the value to |
| Modifiable | Yes. You can use the ALTER SYSTEM SET statement to modify the parameter. |
| Effective upon OBServer node restart | No |
Considerations
We recommend that you use this parameter in scenarios where business indexes have data skew.
- The value
0indicates that the optimizer uses only the row estimation information at the storage layer to calculate the index scanning cost. - The value
10indicates that the optimizer calculates the index scanning cost by adding 10% of the statistics cost and 90% of the storage layer information cost. - The value
100indicates that the optimizer uses only statistics to calculate the index scanning cost.
Examples
systenantDisable index selection optimization for all tenants:
obclient> ALTER SYSTEM SET optimizer_index_cost_adj=0 tenant=all_user;Enable index selection optimization:
obclient> ALTER SYSTEM SET optimizer_index_cost_adj=10 tenant=all_user;
MySQL tenant
Disable index selection optimization for the current tenant:
obclient> ALTER SYSTEM SET optimizer_index_cost_adj=0;Enable index selection optimization:
obclient> ALTER SYSTEM SET optimizer_index_cost_adj=10;
Oracle tenant
Disable index selection optimization for the current tenant:
obclient> ALTER SYSTEM SET "optimizer_index_cost_adj"=0;Enable index selection optimization:
obclient> ALTER SYSTEM SET "optimizer_index_cost_adj"=10;