Note
For V4.6.0, this parameter is available starting with V4.6.0.
Description
ob_vector_index_active_segment_max_size specifies the maximum memory usage of an active segment in a partition. When the memory usage of the active segment exceeds this threshold, the system triggers a freeze and persistence operation to write the incremental data in memory to disk.
Applicability
This parameter is applicable only to OceanBase Database in MySQL mode.
Privilege requirements
Query the parameter
The
systenant and MySQL user tenants can query the parameter by using theSHOW PARAMETERSstatement or theGV$OB_PARAMETERSview.Modify the parameter
The
systenant and MySQL user tenants can modify the parameter.
Attributes
| Attribute | Description |
|---|---|
| Parameter type | Cap |
| Default value | 0, indicating adaptive. The system automatically sets different thresholds based on the available vector memory of the tenant:
|
| Value range | [0, +∞), unit: MB |
| Modifiable | Yes. You can use the ALTER SYSTEM SET statement to modify the parameter. |
| Effective upon OBServer node restart | No. The setting takes effect immediately. |
Considerations
- Increase the threshold: This reduces the frequency of freezing, thereby avoiding the creation of excessive active segments during high-speed incremental writes, which can degrade search performance.
- Decrease the threshold: We recommend that you do not decrease the threshold in most scenarios. Frequent freezing operations can degrade overall search performance.
- Restart the database: If the threshold is too large, the system will take a longer time to restore memory data during a restart. We recommend that you decrease the threshold before a restart to reduce the time required for memory data restoration. Alternatively, you can restart the database during off-peak hours.
Examples
Set the maximum memory usage of an active segment in a partition to 256 MB.
ALTER SYSTEM SET ob_vector_index_active_segment_max_size = '256MB';
Query the current configuration.
SHOW PARAMETERS LIKE 'ob_vector_index_active_segment_max_size';