org.apache.druid.query.groupby.strategy

Class GroupByStrategyV1

java.lang.Object

org.apache.druid.query.groupby.strategy.GroupByStrategyV1

All Implemented Interfaces:

GroupByStrategy

public class GroupByStrategyV1
extends Object
implements GroupByStrategy

Constructor Summary

Constructors

Constructor and Description
GroupByStrategyV1(com.google.common.base.Supplier<GroupByQueryConfig> configSupplier, GroupByQueryEngine engine, QueryWatcher queryWatcher, NonBlockingPool<ByteBuffer> bufferPool)

Method Summary

Modifier and Type	Method and Description
Sequence<ResultRow>	applyPostProcessing(Sequence<ResultRow> results, GroupByQuery query) Apply the GroupByQuery "postProcessingFn", which is responsible for HavingSpec and LimitSpec.
boolean	doMergeResults(GroupByQuery query) Indicates if this query should undergo "mergeResults" or not.
boolean	isCacheable(boolean willMergeRunners) Indicates if results from this query are cacheable or not.
Sequence<ResultRow>	mergeResults(QueryRunner<ResultRow> baseRunner, GroupByQuery query, ResponseContext responseContext) Runs a provided QueryRunner on a provided GroupByQuery, which is assumed to return rows that are properly sorted (by timestamp and dimensions) but not necessarily fully merged (that is, there may be adjacent rows with the same timestamp and dimensions) and without PostAggregators computed.
QueryRunner<ResultRow>	mergeRunners(com.google.common.util.concurrent.ListeningExecutorService exec, Iterable<QueryRunner<ResultRow>> queryRunners) Merge a variety of single-segment query runners into a combined runner.
GroupByQueryResource	prepareResource(GroupByQuery query) Initializes resources required to run GroupByQueryQueryToolChest.mergeResults(QueryRunner) for a particular query.
Sequence<ResultRow>	process(GroupByQuery query, StorageAdapter storageAdapter) Process a groupBy query on a single StorageAdapter.
Sequence<ResultRow>	processSubqueryResult(GroupByQuery subquery, GroupByQuery query, GroupByQueryResource resource, Sequence<ResultRow> subqueryResult, boolean wasQueryPushedDown) Called by GroupByQueryQueryToolChest.mergeResults(QueryRunner) when it needs to process a subquery.
Sequence<ResultRow>	processSubtotalsSpec(GroupByQuery query, GroupByQueryResource resource, Sequence<ResultRow> queryResult) Called by GroupByQueryQueryToolChest.mergeResults(QueryRunner) when it needs to generate subtotals.
boolean	supportsNestedQueryPushDown() Returns whether this strategy supports pushing down outer queries.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.druid.query.groupby.strategy.GroupByStrategy

createMergeFn, createResultComparator

Constructor Detail

GroupByStrategyV1

@Inject
public GroupByStrategyV1(com.google.common.base.Supplier<GroupByQueryConfig> configSupplier,
                                 GroupByQueryEngine engine,
                                 QueryWatcher queryWatcher,
                                 NonBlockingPool<ByteBuffer> bufferPool)

Method Detail

prepareResource

public GroupByQueryResource prepareResource(GroupByQuery query)

Description copied from interface: GroupByStrategy

Initializes resources required to run GroupByQueryQueryToolChest.mergeResults(QueryRunner) for a particular query. That method is also the primary caller of this method. Used by GroupByQueryQueryToolChest.mergeResults(QueryRunner).

Specified by:

prepareResource in interface GroupByStrategy

Parameters:

query - a groupBy query to be processed

Returns:

broker resource

isCacheable

public boolean isCacheable(boolean willMergeRunners)

Description copied from interface: GroupByStrategy

Indicates if results from this query are cacheable or not. Used by GroupByQueryQueryToolChest.getCacheStrategy(GroupByQuery).

Specified by:

isCacheable in interface GroupByStrategy

Parameters:

willMergeRunners - indicates that QueryRunnerFactory.mergeRunners(ExecutorService, Iterable) will be called on the cached by-segment results. Can be used to distinguish if we are running on a broker or data node.

Returns:

true if this strategy is cacheable, otherwise false.

doMergeResults

public boolean doMergeResults(GroupByQuery query)

Description copied from interface: GroupByStrategy

Indicates if this query should undergo "mergeResults" or not. Checked by GroupByQueryQueryToolChest.mergeResults(QueryRunner).

Specified by:

doMergeResults in interface GroupByStrategy

mergeResults

public Sequence<ResultRow> mergeResults(QueryRunner<ResultRow> baseRunner,
                                        GroupByQuery query,
                                        ResponseContext responseContext)

Description copied from interface: GroupByStrategy

Runs a provided QueryRunner on a provided GroupByQuery, which is assumed to return rows that are properly sorted (by timestamp and dimensions) but not necessarily fully merged (that is, there may be adjacent rows with the same timestamp and dimensions) and without PostAggregators computed. This method will fully merge the rows, apply PostAggregators, and return the resulting Sequence. The query will be modified before passing it down to the base runner. For example, "having" clauses will be removed and various context parameters will be adjusted. Despite the similar name, this method is much reduced in scope compared to GroupByQueryQueryToolChest.mergeResults(QueryRunner). That method does delegate to this one at some points, but has a truckload of other responsibility, including computing outer query results (if there are subqueries), computing subtotals (like GROUPING SETS), and computing the havingSpec and limitSpec.

Specified by:

mergeResults in interface GroupByStrategy

Parameters:

baseRunner - base query runner

query - the groupBy query to run inside the base query runner

responseContext - the response context to pass to the base query runner

Returns:

merged result sequence

applyPostProcessing

public Sequence<ResultRow> applyPostProcessing(Sequence<ResultRow> results,
                                               GroupByQuery query)

Description copied from interface: GroupByStrategy

Apply the GroupByQuery "postProcessingFn", which is responsible for HavingSpec and LimitSpec.

Specified by:

applyPostProcessing in interface GroupByStrategy

Parameters:

results - sequence of results

query - the groupBy query

Returns:

post-processed results, with HavingSpec and LimitSpec applied

processSubqueryResult

public Sequence<ResultRow> processSubqueryResult(GroupByQuery subquery,
                                                 GroupByQuery query,
                                                 GroupByQueryResource resource,
                                                 Sequence<ResultRow> subqueryResult,
                                                 boolean wasQueryPushedDown)

Description copied from interface: GroupByStrategy

Called by GroupByQueryQueryToolChest.mergeResults(QueryRunner) when it needs to process a subquery.

Specified by:

processSubqueryResult in interface GroupByStrategy

Parameters:

subquery - inner query

query - outer query

resource - resources returned by GroupByStrategy.prepareResource(GroupByQuery)

subqueryResult - result rows from the subquery

wasQueryPushedDown - true if the outer query was pushed down (so we only need to merge the outer query's results, not run it from scratch like a normal outer query)

Returns:

results of the outer query

processSubtotalsSpec

public Sequence<ResultRow> processSubtotalsSpec(GroupByQuery query,
                                                GroupByQueryResource resource,
                                                Sequence<ResultRow> queryResult)

Description copied from interface: GroupByStrategy

Called by GroupByQueryQueryToolChest.mergeResults(QueryRunner) when it needs to generate subtotals.

Specified by:

processSubtotalsSpec in interface GroupByStrategy

Parameters:

query - query that has a "subtotalsSpec"

resource - resources returned by GroupByStrategy.prepareResource(GroupByQuery)

queryResult - result rows from the main query

Returns:

results for each list of subtotals in the query, concatenated together

mergeRunners

public QueryRunner<ResultRow> mergeRunners(com.google.common.util.concurrent.ListeningExecutorService exec,
                                           Iterable<QueryRunner<ResultRow>> queryRunners)

Description copied from interface: GroupByStrategy

Merge a variety of single-segment query runners into a combined runner. Used by GroupByQueryRunnerFactory.mergeRunners(ExecutorService, Iterable). In that sense, it is intended to go along with GroupByStrategy.process(GroupByQuery, StorageAdapter) (the runners created by that method will be fed into this method). This method is only called on data servers, like Historicals (not the Broker).

Specified by:

mergeRunners in interface GroupByStrategy

Parameters:

exec - executor service used for parallel execution of the query runners

queryRunners - collection of query runners to merge

Returns:

merged query runner

process

public Sequence<ResultRow> process(GroupByQuery query,
                                   StorageAdapter storageAdapter)

Description copied from interface: GroupByStrategy

Process a groupBy query on a single StorageAdapter. This is used by GroupByQueryRunnerFactory.createRunner(org.apache.druid.segment.Segment) to create per-segment QueryRunners. This method is only called on data servers, like Historicals (not the Broker).

Specified by:

process in interface GroupByStrategy

Parameters:

query - the groupBy query

storageAdapter - storage adatper for the segment in question

Returns:

result sequence for the storage adapter

supportsNestedQueryPushDown

public boolean supportsNestedQueryPushDown()

Description copied from interface: GroupByStrategy

Returns whether this strategy supports pushing down outer queries. This is used by GroupByQueryQueryToolChest.mergeResults(QueryRunner) when it decides whether or not to push down an outer query from the Broker to data servers, like Historicals. Can be removed when the "v1" groupBy strategy is removed. ("v1" returns false, and "v2" returns true.)

Specified by:

supportsNestedQueryPushDown in interface GroupByStrategy