public abstract class QueryToolChest<ResultType,QueryType extends Query<ResultType>> extends Object
Constructor and Description |
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QueryToolChest() |
Modifier and Type | Method and Description |
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<T extends LogicalSegment> |
filterSegments(QueryType 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.
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<T> CacheStrategy<ResultType,T,QueryType> |
getCacheStrategy(QueryType query)
Returns a CacheStrategy to be used to load data into the cache and remove it from the cache.
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abstract com.fasterxml.jackson.core.type.TypeReference<ResultType> |
getResultTypeReference()
Returns a TypeReference object that is just passed through to Jackson in order to deserialize
the results of this type of query.
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abstract QueryMetrics<? super QueryType> |
makeMetrics(QueryType query)
Creates a
QueryMetrics object that is used to generate metrics for this specific query type. |
com.google.common.base.Function<ResultType,ResultType> |
makePostComputeManipulatorFn(QueryType query,
MetricManipulationFn fn)
Generally speaking this is the exact same thing as makePreComputeManipulatorFn.
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abstract com.google.common.base.Function<ResultType,ResultType> |
makePreComputeManipulatorFn(QueryType 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.
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abstract QueryRunner<ResultType> |
mergeResults(QueryRunner<ResultType> runner)
This method wraps a QueryRunner.
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QueryRunner<ResultType> |
postMergeQueryDecoration(QueryRunner<ResultType> runner)
Wraps a QueryRunner.
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QueryRunner<ResultType> |
preMergeQueryDecoration(QueryRunner<ResultType> runner)
Wraps a QueryRunner.
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public abstract QueryRunner<ResultType> mergeResults(QueryRunner<ResultType> runner)
runner
- A QueryRunner that provides a series of ResultType objects in time order (ascending or descending)public abstract QueryMetrics<? super QueryType> makeMetrics(QueryType query)
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.
query
- The query that is being processedpublic abstract com.google.common.base.Function<ResultType,ResultType> makePreComputeManipulatorFn(QueryType query, MetricManipulationFn fn)
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.
query
- The Query that is currently being processedfn
- The function that should be applied to all metrics in the resultspublic com.google.common.base.Function<ResultType,ResultType> makePostComputeManipulatorFn(QueryType query, MetricManipulationFn fn)
This should never actually be overridden and it should be removed as quickly as possible.
query
- The Query that is currently being processedfn
- The function that should be applied to all metrics in the resultspublic abstract com.fasterxml.jackson.core.type.TypeReference<ResultType> getResultTypeReference()
@Nullable public <T> CacheStrategy<ResultType,T,QueryType> getCacheStrategy(QueryType query)
This is optional. If it returns null, caching is effectively disabled for the query.
T
- The type of object that will be stored in the cachequery
- The query whose results might be cachedpublic QueryRunner<ResultType> preMergeQueryDecoration(QueryRunner<ResultType> runner)
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.
runner
- The runner to be wrappedpublic QueryRunner<ResultType> postMergeQueryDecoration(QueryRunner<ResultType> runner)
In fact, the input value of this method is always the return value from 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.
runner
- The runner to be wrappedpublic <T extends LogicalSegment> List<T> filterSegments(QueryType query, List<T> segments)
T
- A Generic parameter because Java is coolquery
- The query being processedsegments
- The list of candidate segments to be queriedCopyright © 2011–2018. All rights reserved.