org.apache.druid.query.datasourcemetadata

Class DataSourceQueryQueryToolChest

java.lang.Object

org.apache.druid.query.QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

org.apache.druid.query.datasourcemetadata.DataSourceQueryQueryToolChest

public class DataSourceQueryQueryToolChest
extends QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Constructor Summary

Constructors

Constructor and Description
DataSourceQueryQueryToolChest(GenericQueryMetricsFactory queryMetricsFactory)

Method Summary

Modifier and Type	Method and Description
<T extends LogicalSegment> List<T>	filterSegments(DataSourceMetadataQuery query, List<T> segments) This method is called to allow the query to prune segments that it does not believe need to actually be queried.
CacheStrategy	getCacheStrategy(DataSourceMetadataQuery query) Returns a CacheStrategy to be used to load data into the cache and remove it from the cache.
com.fasterxml.jackson.core.type.TypeReference<Result<DataSourceMetadataResultValue>>	getResultTypeReference() Returns a TypeReference object that is just passed through to Jackson in order to deserialize the results of this type of query.
QueryMetrics<Query<?>>	makeMetrics(DataSourceMetadataQuery query) Creates a QueryMetrics object that is used to generate metrics for this specific query type.
com.google.common.base.Function<Result<DataSourceMetadataResultValue>,Result<DataSourceMetadataResultValue>>	makePreComputeManipulatorFn(DataSourceMetadataQuery query, MetricManipulationFn fn) Creates a Function that can take in a ResultType and return a new ResultType having applied the MetricManipulatorFn to each of the metrics.
QueryRunner<Result<DataSourceMetadataResultValue>>	mergeResults(QueryRunner<Result<DataSourceMetadataResultValue>> runner) This method wraps a QueryRunner.

Methods inherited from class org.apache.druid.query.QueryToolChest

canPerformSubquery, createMergeFn, createResultComparator, decorateObjectMapper, getBaseResultType, getBySegmentResultType, makePostComputeManipulatorFn, postMergeQueryDecoration, preMergeQueryDecoration, resultArraySignature, resultsAsArrays

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

DataSourceQueryQueryToolChest

@Inject
public DataSourceQueryQueryToolChest(GenericQueryMetricsFactory queryMetricsFactory)

Method Detail

filterSegments

public <T extends LogicalSegment> List<T> filterSegments(DataSourceMetadataQuery query,
                                                         List<T> segments)

Description copied from class: QueryToolChest

This method is called to allow the query to prune segments that it does not believe need to actually be queried. It can use whatever criteria it wants in order to do the pruning, it just needs to return the list of Segments it actually wants to see queried.

Overrides:

filterSegments in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Type Parameters:

T - A Generic parameter because Java is cool

Parameters:

query - The query being processed

segments - The list of candidate segments to be queried

Returns:

The list of segments to actually query

mergeResults

public QueryRunner<Result<DataSourceMetadataResultValue>> mergeResults(QueryRunner<Result<DataSourceMetadataResultValue>> runner)

Description copied from class: QueryToolChest

This method wraps a QueryRunner. The input QueryRunner, by contract, will provide a series of ResultType objects in time order (ascending or descending). This method should return a new QueryRunner that potentially merges the stream of ordered ResultType objects. A default implementation constructs a ResultMergeQueryRunner which creates a CombiningSequence using the supplied QueryRunner with QueryToolChest.createResultComparator(Query) and QueryToolChest.createMergeFn(Query)} supplied by this toolchest.

Overrides:

mergeResults in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Parameters:

runner - A QueryRunner that provides a series of ResultType objects in time order (ascending or descending)

Returns:

a QueryRunner that potentially merges the stream of ordered ResultType objects

makeMetrics

public QueryMetrics<Query<?>> makeMetrics(DataSourceMetadataQuery query)

Description copied from class: QueryToolChest

Creates a QueryMetrics object that is used to generate metrics for this specific query type. This exists to allow for query-specific dimensions and metrics. That is, the ToolChest is expected to set some meaningful dimensions for metrics given this query type. Examples might be the topN threshold for a TopN query or the number of dimensions included for a groupBy query.

QueryToolChests for query types in core (druid-processing) and public extensions (belonging to the Druid source tree) should use delegate this method to GenericQueryMetricsFactory.makeMetrics(Query) on an injected instance of GenericQueryMetricsFactory, as long as they don't need to emit custom dimensions and/or metrics.

If some custom dimensions and/or metrics should be emitted for a query type, a plan described in "Making subinterfaces of QueryMetrics" section in QueryMetrics's class-level Javadocs should be followed.

One way or another, this method should ensure that QueryMetrics.query(Query) is called with the given query passed on the created QueryMetrics object before returning.

Specified by:

makeMetrics in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Parameters:

query - The query that is being processed

Returns:

A QueryMetrics that can be used to make metrics for the provided query

makePreComputeManipulatorFn

public com.google.common.base.Function<Result<DataSourceMetadataResultValue>,Result<DataSourceMetadataResultValue>> makePreComputeManipulatorFn(DataSourceMetadataQuery query,
                                                                                                                                                MetricManipulationFn fn)

Description copied from class: QueryToolChest

Creates a Function that can take in a ResultType and return a new ResultType having applied the MetricManipulatorFn to each of the metrics.

This exists because the QueryToolChest is the only thing that understands the internal serialization format of ResultType, so it's primary responsibility is to "decompose" that structure and apply the given function to all metrics.

This function is called very early in the processing pipeline on the Broker.

Specified by:

makePreComputeManipulatorFn in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Parameters:

query - The Query that is currently being processed

fn - The function that should be applied to all metrics in the results

Returns:

A function that will apply the provided fn to all metrics in the input ResultType object

getResultTypeReference

public com.fasterxml.jackson.core.type.TypeReference<Result<DataSourceMetadataResultValue>> getResultTypeReference()

Description copied from class: QueryToolChest

Returns a TypeReference object that is just passed through to Jackson in order to deserialize the results of this type of query.

Specified by:

getResultTypeReference in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Returns:

A TypeReference to indicate to Jackson what type of data will exist for this query

getCacheStrategy

public CacheStrategy getCacheStrategy(DataSourceMetadataQuery query)

Description copied from class: QueryToolChest

Returns a CacheStrategy to be used to load data into the cache and remove it from the cache.

This is optional. If it returns null, caching is effectively disabled for the query.

Overrides:

getCacheStrategy in class QueryToolChest<Result<DataSourceMetadataResultValue>,DataSourceMetadataQuery>

Parameters:

query - The query whose results might be cached

Returns:

A CacheStrategy that can be used to populate and read from the Cache