SHOW REBALANCE ALL DATABASES STATUS

Syntax

SQL

SHOW REBALANCE ALL DATABASES STATUS;

Remarks

Alternatively, you can query the information schema view MV_REBALANCE_STATUS , which returns the same output as the SHOW REBALANCE ALL DATABASES STATUS command.

The Ordinal is the target partition’s ordinal, and the Target_Host and Target_Port correspond to the destination leaf. Any two operations in the same Phase can be run in parallel and phases are run in order. For example, the aggregator can run COPY PARTITION on partitions test:1 and test:3 in parallel. The exact meaning of what each phase means is arbitrary and depends on the particular rebalance operation.

Estimated_Time_Remaining_Ms

The Estimated_Time_Remaining_Ms column contains an estimate (in milliseconds) for each low-level command as follows:

Command is running
- The estimate is the remaining time for the command to complete.
- For a running COPY PARTITION operation, the engine obtains the remaining-time estimate from the ESTIMATED_CATCHUP_TIME_S column in the MV_REPLICATION_STATUS information schema view and converts it to milliseconds. For a running PROMOTE operation, the engine uses the larger of the catch-up estimate and the replay estimate. If the live estimates are not available, the value is NULL.
Command has not started
- The estimate is the expected runtime of the command.
- For commands that have not started, EXPLAIN REBALANCE, and other action types (such as DROP PARTITION), SingleStore uses a per-database, per-action-type exponential moving average of previous completed runtimes. The latest measurement has a weight of 0.1, and the stored average has a weight of 0.9.

The estimate is based on historical runs for the same database and action type, and its accuracy depends on how well the previous runs reflect current conditions. It is not a confidence interval and does not automatically account for changes in data volume between infrequent rebalance operations.

Example

Run the following command to rebalance partitions on all databases in the cluster:

SQL

REBALANCE ALL DATABASES;

View the status of REBALANCE ALL DATABASES while it is still running:

SQL

SHOW REBALANCE ALL DATABASES STATUS;

+----------+-----------------------------------+---------+-------------+-------------+-------+-----------+--------------+-----------------------------+
| Database | Action                            | Ordinal | Target_Host | Target_Port | Phase | Status    | Running_Time | Estimated_Time_Remaining_Ms |
+----------+-----------------------------------+---------+-------------+-------------+-------+-----------+--------------+-----------------------------+
| x_db     | COPY PARTITION                    | 13      | 127.0.0.1   | 10002       | 3     | success   | 4009         | 0                           |
| x_db     | COPY PARTITION                    | 2       | 127.0.0.1   | 10003       | 4     | success   | 5109         | 0                           |
| x_db     | COPY PARTITION                    | 2       | 127.0.0.1   | 10004       | 4     | success   | 5112         | 0                           |
| x_db     | PROMOTE PARTITION WITH DROP FORCE | 2       | 127.0.0.1   | 10003       | 5     | running   | 405          | 1130                        |
| x_db     | DROP PARTITION                    | 2       | 127.0.0.1   | 10002       | 6     | scheduled | NULL         | 1002                        |
| x_db     | DROP PARTITION                    | 13      | 127.0.0.1   | 10004       | 6     | scheduled | NULL         | 1002                        |
+----------+-----------------------------------+---------+-------------+-------------+-------+-----------+--------------+-----------------------------+

Note: The Status displays success for the activities that are already complete. The Estimated_Time_Remaining_Ms displays the estimated remaining time (in milliseconds) for each low-level command to complete.