EXPLAIN REBALANCE PARTITIONS

Returns the set of steps that REBALANCE PARTITIONS would run if you executed it now.

Syntax

EXPLAIN REBALANCE PARTITIONS ON db_name

Remarks

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. The Estimated_Time_Remaining_Ms is the estimated total time (in milliseconds) that each low-level command will take to complete.

Example

EXPLAIN REBALANCE PARTITIONS ON memsql_demo;
+-----------------------------+---------+-------------+-------------+-------+-----------------------------+
| Action                      | Ordinal | Target_Host | Target_Port | Phase | Estimated_Time_Remaining_Ms |
+-----------------------------+---------+-------------+-------------+-------+-----------------------------+
| COPY PARTITION              | 13      | 127.0.0.1   | 10002       | 3     | 7821                        |
| COPY PARTITION              | 2       | 127.0.0.1   | 10003       | 4     | 7821                        |
| COPY PARTITION              | 2       | 127.0.0.1   | 10004       | 4     | 7821                        |
| PROMOTE PARTITION WITH DROP | 2       | 127.0.0.1   | 10003       | 5     | 1351                        |
| DROP PARTITION              | 2       | 127.0.0.1   | 10002       | 6     | 1002                        |
| DROP PARTITION              | 13      | 127.0.0.1   | 10004       | 6     | 1002                        |
+-----------------------------+---------+-------------+-------------+-------+-----------------------------+

Note: The Estimated_Time_Remaining_Ms is the estimated total time (in milliseconds) that each low-level command will take to complete.

Understanding the Rebalance Actions

Each action occurs on a single partition.

Action

Definition

COPY PARTITION

Copies a partition and sets up replication to keep the copy in sync.

PROMOTE PARTITION [WITH {DROP,REPOINT}]

Promotes a replica partition into a master partition. The WITH DROP clause drops the previous master partition. The WITH REPOINT clause converts the previous master partition into a replica partition. There is no default, rebalance chooses one or the other based on the path to get to a balanced set of partitions.

DROP PARTITION

Drops a partition.

Last modified: May 24, 2023

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