Package org.apache.druid.query.topn.types

Class StringTopNColumnAggregatesProcessor

java.lang.Object

org.apache.druid.query.topn.types.StringTopNColumnAggregatesProcessor

All Implemented Interfaces:

ColumnSelectorStrategy, TopNColumnAggregatesProcessor<DimensionSelector>

public class StringTopNColumnAggregatesProcessor
extends Object
implements TopNColumnAggregatesProcessor<DimensionSelector>

Constructor Summary

Constructors

Constructor	Description
StringTopNColumnAggregatesProcessor(ColumnCapabilities capabilities, ColumnType dimensionType)

Method Summary

Modifier and Type	Method	Description
void	closeAggregators()	Closes all on heap Aggregator associated with the aggregates processor
int	getCardinality(DimensionSelector selector)	Get value cardinality of underlying ColumnValueSelector
Aggregator[][]	getRowSelector(TopNQuery query, TopNParams params, TopNCursorInspector cursorInspector)	Used by HeapBasedTopNAlgorithm.
void	initAggregateStore()	Initializes the underlying aggregates store to something nice and seleector type appropriate
long	scanAndAggregate(TopNQuery query, DimensionSelector selector, Cursor cursor, CursorGranularizer granularizer, Aggregator[][] rowSelector)	Used by HeapBasedTopNAlgorithm.
void	updateResults(TopNResultBuilder resultBuilder)	Used by HeapBasedTopNAlgorithm.

Methods inherited from class java.lang.Object

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

Constructor Details

StringTopNColumnAggregatesProcessor

public StringTopNColumnAggregatesProcessor(ColumnCapabilities capabilities,
 ColumnType dimensionType)

Method Details

getCardinality

public int getCardinality(DimensionSelector selector)

Description copied from interface: TopNColumnAggregatesProcessor

Get value cardinality of underlying ColumnValueSelector

Specified by:

getCardinality in interface TopNColumnAggregatesProcessor<DimensionSelector>

getRowSelector

public Aggregator[][] getRowSelector(TopNQuery query,
 TopNParams params,
 TopNCursorInspector cursorInspector)

Description copied from interface: TopNColumnAggregatesProcessor

Used by HeapBasedTopNAlgorithm. 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, e.g. string columns where the value cardinality is known. A dimension type that does not have integer values should return null.

Specified by:

getRowSelector in interface TopNColumnAggregatesProcessor<DimensionSelector>

Parameters:

query - The TopN query being served

params - Parameters for the TopN query being served

cursorInspector - provide information about the cursor 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

updateResults

public void updateResults(TopNResultBuilder resultBuilder)

Description copied from interface: TopNColumnAggregatesProcessor

Used by HeapBasedTopNAlgorithm. 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:

updateResults in interface TopNColumnAggregatesProcessor<DimensionSelector>

Parameters:

resultBuilder - TopN result builder

closeAggregators

public void closeAggregators()

Description copied from interface: TopNColumnAggregatesProcessor

Closes all on heap Aggregator associated with the aggregates processor

Specified by:

closeAggregators in interface TopNColumnAggregatesProcessor<DimensionSelector>

scanAndAggregate

public long scanAndAggregate(TopNQuery query,
 DimensionSelector selector,
 Cursor cursor,
 CursorGranularizer granularizer,
 Aggregator[][] rowSelector)

Description copied from interface: TopNColumnAggregatesProcessor

Used by HeapBasedTopNAlgorithm. The contract of this method requires calling TopNColumnAggregatesProcessor.initAggregateStore() prior to calling this method. 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), usable if value cardinality is known, or from aggregatesStore (slower map). 2. If the rowSelector/aggregatesStore did not have an entry for a particular row value, this function should retrieve the current Aggregator[] using BaseTopNAlgorithm.makeAggregators(org.apache.druid.segment.Cursor, java.util.List<org.apache.druid.query.aggregation.AggregatorFactory>) and the provided cursor and query, storing them in rowSelector/aggregatesStore 3. Call Aggregator.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:

scanAndAggregate in interface TopNColumnAggregatesProcessor<DimensionSelector>

Parameters:

query - The TopN query being served.

selector - Dimension value selector

cursor - Cursor for the segment being queried

rowSelector - Integer lookup containing aggregators

Returns:

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

initAggregateStore

public void initAggregateStore()

Description copied from interface: TopNColumnAggregatesProcessor

Initializes the underlying aggregates store to something nice and seleector type appropriate

Specified by:

initAggregateStore in interface TopNColumnAggregatesProcessor<DimensionSelector>