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Aggregator

Info

Except for the SHOW ... commands, MemSQL Helios does not support the commands mentioned in this topic.

In a MemSQL cluster, an aggregator is a node that functions as a cluster-aware query router. An aggregator stores only metadata and acts as a gateway into the distributed system. A MemSQL cluster may have one or many aggregators depending on query volume.

An aggregator is responsible for:

  • querying the leaves
  • aggregating the results
  • returning the results to the client

The Master Aggregator is a specialized aggregator responsible for cluster monitoring and failover.

Aggregator Commands

Starting a Master Aggregator

A master aggregator node is started as a MemSQL node without additional parameters. Once started, you can run BOOTSTRAP AGGREGATOR on the node to make it a Master Aggregator. The node must not be part of an existing cluster.

Starting a Child Aggregator

A child aggregator node is started as a MemSQL node without additional parameters. Once started, you can run ADD AGGREGATOR on the Master Aggregator to add the node (as an aggregator) to the cluster.