org.apache.druid.query.topn.types

Class StringTopNColumnSelectorStrategy

java.lang.Object

org.apache.druid.query.topn.types.StringTopNColumnSelectorStrategy

All Implemented Interfaces:

ColumnSelectorStrategy, TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

public class StringTopNColumnSelectorStrategy
extends Object
implements TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

Field Summary

Fields inherited from interface org.apache.druid.query.topn.types.TopNColumnSelectorStrategy

CARDINALITY_UNKNOWN

Constructor Summary

Constructors

Constructor and Description
StringTopNColumnSelectorStrategy(ValueType dimensionType)

Method Summary

Modifier and Type	Method and Description
long	dimExtractionScanAndAggregate(TopNQuery query, DimensionSelector selector, Cursor cursor, Aggregator[][] rowSelector, Map<Comparable<?>,Aggregator[]> aggregatesStore) Used by DimExtractionTopNAlgorithm.
int	getCardinality(DimensionSelector selector)
Aggregator[][]	getDimExtractionRowSelector(TopNQuery query, TopNParams params, StorageAdapter storageAdapter) Used by DimExtractionTopNAlgorithm.
Map<Comparable<?>,Aggregator[]>	makeDimExtractionAggregateStore() Used by DimExtractionTopNAlgorithm.
void	updateDimExtractionResults(Map<Comparable<?>,Aggregator[]> aggregatesStore, TopNResultBuilder resultBuilder) Used by DimExtractionTopNAlgorithm.

Methods inherited from class java.lang.Object

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

Constructor Detail

StringTopNColumnSelectorStrategy

public StringTopNColumnSelectorStrategy(ValueType dimensionType)

Method Detail

getCardinality

public int getCardinality(DimensionSelector selector)

Specified by:

getCardinality in interface TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

getDimExtractionRowSelector

public Aggregator[][] getDimExtractionRowSelector(TopNQuery query,
                                                  TopNParams params,
                                                  StorageAdapter storageAdapter)

Description copied from interface: TopNColumnSelectorStrategy

Used by DimExtractionTopNAlgorithm. Create an Aggregator[][] using BaseTopNAlgorithm.AggregatorArrayProvider and the given parameters. As the Aggregator[][] is used as an integer-based lookup, this method is only applicable for dimension types that use integer row values. A dimension type that does not have integer values should return null.

Specified by:

getDimExtractionRowSelector in interface TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

Parameters:

query - The TopN query being served

params - Parameters for the TopN query being served

storageAdapter - Column storage adapter, to provide information about the column that can be used for query optimization, e.g. whether dimension values are sorted or not

Returns:

an Aggregator[][] for integer-valued dimensions, null otherwise

makeDimExtractionAggregateStore

public Map<Comparable<?>,Aggregator[]> makeDimExtractionAggregateStore()

Description copied from interface: TopNColumnSelectorStrategy

Used by DimExtractionTopNAlgorithm. Creates an aggregate store map suitable for this strategy's type that will be passed to dimExtractionScanAndAggregate() and updateDimExtractionResults().

Specified by:

makeDimExtractionAggregateStore in interface TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

Returns:

Aggregate store map

dimExtractionScanAndAggregate

public long dimExtractionScanAndAggregate(TopNQuery query,
                                          DimensionSelector selector,
                                          Cursor cursor,
                                          Aggregator[][] rowSelector,
                                          Map<Comparable<?>,Aggregator[]> aggregatesStore)

Description copied from interface: TopNColumnSelectorStrategy

Used by DimExtractionTopNAlgorithm. Iterate through the cursor, reading the current row from a dimension value selector, and for each row value: 1. Retrieve the Aggregator[] for the row value from rowSelector (fast integer lookup) or from aggregatesStore (slower map). 2. If the rowSelector and/or aggregatesStore did not have an entry for a particular row value, this function should retrieve the current Aggregator[] using BaseTopNAlgorithm.makeAggregators() and the provided cursor and query, storing them in rowSelector and aggregatesStore 3. Call aggregate() on each of the aggregators. If a dimension type doesn't have integer values, it should ignore rowSelector and use the aggregatesStore map only.

Specified by:

dimExtractionScanAndAggregate in interface TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

Parameters:

query - The TopN query being served.

selector - Dimension value selector

cursor - Cursor for the segment being queried

rowSelector - Integer lookup containing aggregators

aggregatesStore - Map containing aggregators

Returns:

the number of processed rows (after postFilters are applied inside the cursor being processed)

updateDimExtractionResults

public void updateDimExtractionResults(Map<Comparable<?>,Aggregator[]> aggregatesStore,
                                       TopNResultBuilder resultBuilder)

Description copied from interface: TopNColumnSelectorStrategy

Used by DimExtractionTopNAlgorithm. Read entries from the aggregates store, adding the keys and associated values to the resultBuilder, applying the valueTransformer to the keys if present

Specified by:

updateDimExtractionResults in interface TopNColumnSelectorStrategy<DimensionSelector,Map<Comparable<?>,Aggregator[]>>

Parameters:

aggregatesStore - Map created by makeDimExtractionAggregateStore()

resultBuilder - TopN result builder