io.druid.query.topn.types

Interface TopNColumnSelectorStrategy<ValueSelectorType extends ColumnValueSelector,DimExtractionAggregateStoreType extends Map>

All Superinterfaces:

ColumnSelectorStrategy

All Known Implementing Classes:

NumericTopNColumnSelectorStrategy, StringTopNColumnSelectorStrategy

public interface TopNColumnSelectorStrategy<ValueSelectorType extends ColumnValueSelector,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, Capabilities capabilities) Used by DimExtractionTopNAlgorithm.
ValueType	getValueType()
DimExtractionAggregateStoreType	makeDimExtractionAggregateStore() Used by DimExtractionTopNAlgorithm.
void	updateDimExtractionResults(DimExtractionAggregateStoreType aggregatesStore, com.google.common.base.Function<Object,Object> valueTransformer, 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)

getValueType

ValueType getValueType()

getDimExtractionRowSelector

Aggregator[][] getDimExtractionRowSelector(TopNQuery query,
                                           TopNParams params,
                                           Capabilities capabilities)

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

capabilities - Object indicating if dimension values are sorted

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,
                                @Nullable
                                com.google.common.base.Function<Object,Object> valueTransformer,
                                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()

valueTransformer - Converts keys to different types, if null no conversion is needed

resultBuilder - TopN result builder