When do I rebalance partitions?
When the data on a cluster is distributed, and specific leaf nodes do not have partitions of data for databases within that cluster, a rebalance is needed.
Specifically, the rebalance operation re-distributes data across the cluster so that data is more evenly distributed.
You can check if you need to perform a rebalance by running this command on each database, you would like to check:
EXPLAIN REBALANCE PARTITIONS ON db_name;
Running the rebalance partitions command with EXPLAIN will show you the steps the command intends to perform when running it without the EXPLAIN keyword.
Alternatively, as of SingleStore version 7.3, you can check all databases with one command:
EXPLAIN REBALANCE ALL DATABASES;