org.apache.druid.query.topn.types

Interface TopNColumnSelectorStrategy<ValueSelectorType,DimExtractionAggregateStoreType extends Map>

All Superinterfaces:

ColumnSelectorStrategy

All Known Implementing Classes:

NumericTopNColumnSelectorStrategy, StringTopNColumnSelectorStrategy

public interface TopNColumnSelectorStrategy<ValueSelectorType,DimExtractionAggregateStoreType extends Map>
extends ColumnSelectorStrategy

Field Summary

Fields

Modifier and Type	Field and Description
static int	CARDINALITY_UNKNOWN

Method Summary

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

Field Detail

CARDINALITY_UNKNOWN

static final int CARDINALITY_UNKNOWN

See Also:

Constant Field Values

Method Detail

getCardinality

int getCardinality(ValueSelectorType selector)

getDimExtractionRowSelector

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

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.

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

DimExtractionAggregateStoreType makeDimExtractionAggregateStore()

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

Returns:

Aggregate store map

dimExtractionScanAndAggregate

long dimExtractionScanAndAggregate(TopNQuery query,
                                   ValueSelectorType selector,
                                   Cursor cursor,
                                   Aggregator[][] rowSelector,
                                   DimExtractionAggregateStoreType aggregatesStore)

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.

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

void updateDimExtractionResults(DimExtractionAggregateStoreType aggregatesStore,
                                TopNResultBuilder resultBuilder)

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

Parameters:

aggregatesStore - Map created by makeDimExtractionAggregateStore()

resultBuilder - TopN result builder