Package org.apache.druid.query.timeboundary

Class TimeBoundaryQueryQueryToolChest

java.lang.Object

org.apache.druid.query.QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

org.apache.druid.query.timeboundary.TimeBoundaryQueryQueryToolChest

public class TimeBoundaryQueryQueryToolChest
extends QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

Constructor Summary

Constructors

Constructor	Description
TimeBoundaryQueryQueryToolChest()
TimeBoundaryQueryQueryToolChest(GenericQueryMetricsFactory queryMetricsFactory)

Method Summary

Modifier and Type	Method	Description
BinaryOperator<Result<TimeBoundaryResultValue>>	createMergeFn(Query<Result<TimeBoundaryResultValue>> query)	Creates a merge function that is used to merge intermediate aggregates from historicals in broker.
Comparator<Result<TimeBoundaryResultValue>>	createResultComparator(Query<Result<TimeBoundaryResultValue>> query)	Creates an ordering comparator that is used to order results.
<T extends LogicalSegment> List<T>	filterSegments(TimeBoundaryQuery 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<Result<TimeBoundaryResultValue>,Object,TimeBoundaryQuery>	getCacheStrategy(TimeBoundaryQuery 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<TimeBoundaryResultValue>>	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(TimeBoundaryQuery query)	Creates a QueryMetrics object that is used to generate metrics for this specific query type.
com.google.common.base.Function<Result<TimeBoundaryResultValue>,Result<TimeBoundaryResultValue>>	makePreComputeManipulatorFn(TimeBoundaryQuery 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<TimeBoundaryResultValue>>	mergeResults(QueryRunner<Result<TimeBoundaryResultValue>> runner)	This method wraps a QueryRunner.
RowSignature	resultArraySignature(TimeBoundaryQuery query)	Returns a RowSignature for the arrays returned by QueryToolChest.resultsAsArrays(QueryType, org.apache.druid.java.util.common.guava.Sequence<ResultType>).
Sequence<Object[]>	resultsAsArrays(TimeBoundaryQuery query, Sequence<Result<TimeBoundaryResultValue>> resultSequence)	Converts a sequence of this query's ResultType into arrays.

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

canPerformSubquery, decorateObjectMapper, getBaseResultType, getBySegmentResultType, makePostComputeManipulatorFn, postMergeQueryDecoration, preMergeQueryDecoration, resultsAsFrames

Methods inherited from class java.lang.Object

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

Constructor Detail

TimeBoundaryQueryQueryToolChest

public TimeBoundaryQueryQueryToolChest()

TimeBoundaryQueryQueryToolChest

@Inject
public TimeBoundaryQueryQueryToolChest(GenericQueryMetricsFactory queryMetricsFactory)

Method Detail

filterSegments

public <T extends LogicalSegment> List<T> filterSegments(TimeBoundaryQuery 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<TimeBoundaryResultValue>,TimeBoundaryQuery>

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<TimeBoundaryResultValue>> mergeResults(QueryRunner<Result<TimeBoundaryResultValue>> 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 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.

Generally speaking, the logic that exists in makePostComputeManipulatorFn should actually exist in this method. Additionally, if a query supports PostAggregations, this method should take steps to ensure that it computes PostAggregations a minimum number of times. This is most commonly achieved by computing the PostAgg results during merge and also rewriting the query such that it has the minimum number of PostAggs (most often zero).

Overrides:

mergeResults in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

Parameters:

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

Returns:

a QueryRunner that merges the stream of ordered ResultType objects

createMergeFn

public BinaryOperator<Result<TimeBoundaryResultValue>> createMergeFn(Query<Result<TimeBoundaryResultValue>> query)

Description copied from class: QueryToolChest

Creates a merge function that is used to merge intermediate aggregates from historicals in broker. This merge function is used in the default ResultMergeQueryRunner provided by QueryToolChest.mergeResults(QueryRunner) and also used in ParallelMergeCombiningSequence by 'CachingClusteredClient' if it does not return null.

Returning null from this function means that a query does not support result merging, at least via the mechanisms that utilize this function.

Overrides:

createMergeFn in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

createResultComparator

public Comparator<Result<TimeBoundaryResultValue>> createResultComparator(Query<Result<TimeBoundaryResultValue>> query)

Description copied from class: QueryToolChest

Creates an ordering comparator that is used to order results. This comparator is used in the default ResultMergeQueryRunner provided by QueryToolChest.mergeResults(QueryRunner)

Overrides:

createResultComparator in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

makeMetrics

public QueryMetrics<Query<?>> makeMetrics(TimeBoundaryQuery 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<TimeBoundaryResultValue>,TimeBoundaryQuery>

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<TimeBoundaryResultValue>,Result<TimeBoundaryResultValue>> makePreComputeManipulatorFn(TimeBoundaryQuery 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 function's primary purpose is to help work around some challenges that exist around deserializing results across the wire. Specifically, different aggregators will generate different object types in a result set, if we wanted jackson to be able to deserialize these directly, we'd need to generate a response class for each query that jackson could use to deserialize things. That is not what we do. Instead, we have jackson deserialize Object instances and then use a MetricManipulatorFn to convert from those object instances to the actual object that the aggregator expects. As such, this would be more effectively named "makeObjectDeserializingFn".

It is safe and acceptable for implementations of this method to first validate that the MetricManipulationFn is MetricManipulatorFns.DESERIALIZING_INSTANCE and throw an exception if it is not. If such an exception is ever thrown, it is indicative of a bug in the caller which should be fixed by not calling this method with anything other than the deserializing manipulator function.

There are some implementations where this was also tasked with computing PostAggregators, but this is actually not a good place to compute those as this function can be called in a number of cases when PostAggs are not really meaningful to compute. Instead, PostAggs should be computed in the mergeResults call and the mergeResults implementation should take care to ensure that PostAggs are only computed the minimum number of times necessary.

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

Specified by:

makePreComputeManipulatorFn in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

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<TimeBoundaryResultValue>> 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<TimeBoundaryResultValue>,TimeBoundaryQuery>

Returns:

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

getCacheStrategy

public CacheStrategy<Result<TimeBoundaryResultValue>,Object,TimeBoundaryQuery> getCacheStrategy(TimeBoundaryQuery 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<TimeBoundaryResultValue>,TimeBoundaryQuery>

Parameters:

query - The query whose results might be cached

Returns:

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

resultArraySignature

public RowSignature resultArraySignature(TimeBoundaryQuery query)

Description copied from class: QueryToolChest

Returns a RowSignature for the arrays returned by QueryToolChest.resultsAsArrays(QueryType, org.apache.druid.java.util.common.guava.Sequence<ResultType>). The returned signature will be the same length as each array returned by QueryToolChest.resultsAsArrays(QueryType, org.apache.druid.java.util.common.guava.Sequence<ResultType>).

Overrides:

resultArraySignature in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

Parameters:

query - same query passed to QueryToolChest.resultsAsArrays(QueryType, org.apache.druid.java.util.common.guava.Sequence<ResultType>)

Returns:

row signature

resultsAsArrays

public Sequence<Object[]> resultsAsArrays(TimeBoundaryQuery query,
                                          Sequence<Result<TimeBoundaryResultValue>> resultSequence)

Description copied from class: QueryToolChest

Converts a sequence of this query's ResultType into arrays. The array signature is given by QueryToolChest.resultArraySignature(QueryType). This functionality is useful because it allows higher-level processors to operate on the results of any query in a consistent way. This is useful for the SQL layer and for any algorithm that might operate on the results of an inner query.

Not all query types support this method. They will throw UnsupportedOperationException, and they cannot be used by the SQL layer or by generic higher-level algorithms.

Some query types return less information after translating their results into arrays, especially in situations where there is no clear way to translate fully rich results into flat arrays. For example, the scan query does not include the segmentId in its array-based results, because it could potentially conflict with a 'segmentId' field in the actual datasource being scanned.

It is possible that there will be multiple arrays returned for a single result object. For example, in the topN query, each TopNResultValue will generate a separate array for each of its values.

By convention, the array form should include the __time column, if present, as a long (milliseconds since epoch).

Overrides:

resultsAsArrays in class QueryToolChest<Result<TimeBoundaryResultValue>,TimeBoundaryQuery>

resultSequence - results of the form returned by QueryToolChest.mergeResults(org.apache.druid.query.QueryRunner<ResultType>)

Returns:

results in array form