Query

Query enables you to read data out of your Hydrolix cluster. You can scale query resources with Query Pools, which let you sandbox different workflows to avoid "noisy neighbor" performance issues.

You can query Hydrolix in the following ways:

HTTP API
Native Interface
JDBC

Components

The following components comprise Hydrolix's Query architecture:

Data is always stored centrally within the Hydrolix Database storage bucket, no matter how many query pools you create. Because query peers are stateless, they do not cache data in between queries.

Component	Description	Scale to 0
Load Balancer	An application load-balancer used to route traffic to the Query Heads.	Yes
Query Head	Receives queries. Delegates sub-queries on partition ranges to Query Peers. Aggregates Query Peer responses to generate a query result.	Yes
Query Peer Pool	The workers that execute queries. They retrieve partitions from the Hydrolix Database storage bucket and execute their portion of the query on that dataset. Return the result to the Query Head.	Yes
Zookeeper	Used for cluster management of the Query Head and Query Peer pools.	Yes
Hydrolix Database Storage Bucket	Contains the partitions that comprise the database. Part of the core infrastructure.	No
Catalog	Contains metadata regarding data stored in Hydrolix. Part of the core infrastructure.	No

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Try a Query
To get started with writing your first query, see Query.

Query Pools

Because Hydrolix query infrastructure is decoupled from the storage layer, you can create separate query pools for different groups of users. For example, you might configure separate sandboxes for administrator queries, interactive analyst queries, and monitoring queries.

Pool groups support independent scaling, so capacity for each pool can adjust automatically to satisfy demand. You can even scale an entire pool to zero when demand is negligible -- for example, over the weekend when staff have no need to access data. When demand returns, you can scale the pool back up within minutes.

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Configure Query Pools
To configure query pools in your Hydrolix cluster, see Service Pools.