io.druid.query.groupby

Class GroupByQueryQueryToolChest

java.lang.Object

io.druid.query.QueryToolChest<Row,GroupByQuery>

io.druid.query.groupby.GroupByQueryQueryToolChest

public class GroupByQueryQueryToolChest
extends QueryToolChest<Row,GroupByQuery>

Field Summary

Fields

Modifier and Type	Field and Description
static String	GROUP_BY_MERGE_KEY

Constructor Summary

Constructors

Constructor and Description
GroupByQueryQueryToolChest(GroupByStrategySelector strategySelector, IntervalChunkingQueryRunnerDecorator intervalChunkingQueryRunnerDecorator)
GroupByQueryQueryToolChest(GroupByStrategySelector strategySelector, IntervalChunkingQueryRunnerDecorator intervalChunkingQueryRunnerDecorator, GroupByQueryMetricsFactory queryMetricsFactory)

Method Summary

Modifier and Type	Method and Description
static Collection<DimensionSpec>	extractionsToRewrite(GroupByQuery query) This function checks the query for dimensions which can be optimized by applying the dimension extraction as the final step of the query instead of on every event.
CacheStrategy<Row,Object,GroupByQuery>	getCacheStrategy(GroupByQuery 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<Row>	getResultTypeReference() Returns a TypeReference object that is just passed through to Jackson in order to deserialize the results of this type of query.
GroupByQueryMetrics	makeMetrics(GroupByQuery query) Creates a QueryMetrics object that is used to generate metrics for this specific query type.
com.google.common.base.Function<Row,Row>	makePostComputeManipulatorFn(GroupByQuery query, MetricManipulationFn fn) Generally speaking this is the exact same thing as makePreComputeManipulatorFn.
com.google.common.base.Function<Row,Row>	makePreComputeManipulatorFn(GroupByQuery 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<Row>	mergeResults(QueryRunner<Row> runner) This method wraps a QueryRunner.
QueryRunner<Row>	preMergeQueryDecoration(QueryRunner<Row> runner) Wraps a QueryRunner.

Methods inherited from class io.druid.query.QueryToolChest

filterSegments, postMergeQueryDecoration

Methods inherited from class java.lang.Object

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

Field Detail

GROUP_BY_MERGE_KEY

public static final String GROUP_BY_MERGE_KEY

See Also:

Constant Field Values

Constructor Detail

GroupByQueryQueryToolChest

public GroupByQueryQueryToolChest(GroupByStrategySelector strategySelector,
                                  IntervalChunkingQueryRunnerDecorator intervalChunkingQueryRunnerDecorator)

GroupByQueryQueryToolChest

@Inject
public GroupByQueryQueryToolChest(GroupByStrategySelector strategySelector,
                                          IntervalChunkingQueryRunnerDecorator intervalChunkingQueryRunnerDecorator,
                                          GroupByQueryMetricsFactory queryMetricsFactory)

Method Detail

mergeResults

public QueryRunner<Row> mergeResults(QueryRunner<Row> 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.

Specified by:

mergeResults in class QueryToolChest<Row,GroupByQuery>

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 GroupByQueryMetrics makeMetrics(GroupByQuery 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<Row,GroupByQuery>

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<Row,Row> makePreComputeManipulatorFn(GroupByQuery 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<Row,GroupByQuery>

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

makePostComputeManipulatorFn

public com.google.common.base.Function<Row,Row> makePostComputeManipulatorFn(GroupByQuery query,
                                                                             MetricManipulationFn fn)

Description copied from class: QueryToolChest

Generally speaking this is the exact same thing as makePreComputeManipulatorFn. It is leveraged in order to compute PostAggregators on results after they have been completely merged together, which should actually be done in the mergeResults() call instead of here.

This should never actually be overridden and it should be removed as quickly as possible.

Overrides:

makePostComputeManipulatorFn in class QueryToolChest<Row,GroupByQuery>

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<Row> 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<Row,GroupByQuery>

Returns:

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

preMergeQueryDecoration

public QueryRunner<Row> preMergeQueryDecoration(QueryRunner<Row> runner)

Description copied from class: QueryToolChest

Wraps a QueryRunner. The input QueryRunner is the QueryRunner as it exists *before* being passed to mergeResults().

In fact, the return value of this method is always passed to mergeResults, so it is equivalent to just implement this functionality as extra decoration on the QueryRunner during mergeResults().

In the interests of potentially simplifying these interfaces, the recommendation is to actually not override this method and instead apply anything that might be needed here in the mergeResults() call.

Overrides:

preMergeQueryDecoration in class QueryToolChest<Row,GroupByQuery>

Parameters:

runner - The runner to be wrapped

Returns:

The wrapped runner

getCacheStrategy

public CacheStrategy<Row,Object,GroupByQuery> getCacheStrategy(GroupByQuery 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<Row,GroupByQuery>

Parameters:

query - The query whose results might be cached

Returns:

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

extractionsToRewrite

public static Collection<DimensionSpec> extractionsToRewrite(GroupByQuery query)

This function checks the query for dimensions which can be optimized by applying the dimension extraction as the final step of the query instead of on every event.

Parameters:

query - The query to check for optimizations

Returns:

A collection of DimensionsSpec which can be extracted at the last second upon query completion.