Native queries

info

Apache Druid supports two query languages: Druid SQL and native queries. This document describes the native query language. For information about how Druid SQL chooses which native query types to use when it runs a SQL query, refer to the SQL documentation.

Native queries in Druid are JSON objects and are typically issued to the Broker or Router processes. Queries can be posted like this:

curl -X POST '<queryable_host>:<port>/druid/v2/?pretty' -H 'Content-Type:application/json' -H 'Accept:application/json' -d @<query_json_file>

info

Replace <queryable_host>:<port> with the appropriate address and port for your system. For example, if running the quickstart configuration, replace <queryable_host>:<port> with localhost:8888.

You can also enter them directly in the web console’s Query view. Simply pasting a native query into the console switches the editor into JSON mode.

Druid’s native query language is JSON over HTTP, although many members of the community have contributed different client libraries in other languages to query Druid.

The Content-Type/Accept Headers can also take ‘application/x-jackson-smile’.

curl -X POST '<queryable_host>:<port>/druid/v2/?pretty' -H 'Content-Type:application/json' -H 'Accept:application/x-jackson-smile' -d @<query_json_file>

info

If the Accept header is not provided, it defaults to the value of ‘Content-Type’ header.

Druid’s native query is relatively low level, mapping closely to how computations are performed internally. Druid queries are designed to be lightweight and complete very quickly. This means that for more complex analysis, or to build more complex visualizations, multiple Druid queries may be required.

Even though queries are typically made to Brokers or Routers, they can also be accepted by Historical processes and by Peons (task JVMs) that are running stream ingestion tasks. This may be valuable if you want to query results for specific segments that are served by specific processes.

Available queries

Druid has numerous query types for various use cases. Queries are composed of various JSON properties and Druid has different types of queries for different use cases. The documentation for the various query types describe all the JSON properties that can be set.

Aggregation queries

• Timeseries
• TopN
• GroupBy

Metadata queries

• TimeBoundary
• SegmentMetadata
• DatasourceMetadata

Other queries

• Scan
• Search

Which query type should I use?

For aggregation queries, if more than one would satisfy your needs, we generally recommend using Timeseries or TopN whenever possible, as they are specifically optimized for their use cases. If neither is a good fit, you should use the GroupBy query, which is the most flexible.

Query cancellation

Queries can be cancelled explicitly using their unique identifier. If the query identifier is set at the time of query, or is otherwise known, the following endpoint can be used on the Broker or Router to cancel the query.

DELETE /druid/v2/{queryId}

For example, if the query ID is abc123, the query can be cancelled as follows:

curl -X DELETE "http://host:port/druid/v2/abc123"

Query errors

Authentication and authorization failures

For secured Druid clusters, query requests respond with an HTTP 401 response code in case of an authentication failure. For authorization failures, an HTTP 403 response code is returned.

Query execution failures

If a query fails, Druid returns a response with an HTTP response code and a JSON object with the following structure:

{
  "error" : "Query timeout",
  "errorMessage" : "Timeout waiting for task.",
  "errorClass" : "java.util.concurrent.TimeoutException",
  "host" : "druid1.example.com:8083"
}

The fields in the response are:

Possible Druid error codes for the error field include: