org.apache.calcite.rel.metadata

Interface BuiltInMetadata.PopulationSize

All Superinterfaces:

Metadata

Enclosing class:

BuiltInMetadata

public static interface BuiltInMetadata.PopulationSize
extends Metadata

Metadata about the number of distinct values in the original source of a column or set of columns.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	BuiltInMetadata.PopulationSize.Handler Handler API.

Field Summary

Fields

Modifier and Type	Field and Description
static MetadataDef<BuiltInMetadata.PopulationSize>	DEF

Method Summary

Modifier and Type	Method and Description
@Nullable Double	getPopulationSize(ImmutableBitSet groupKey) Estimates the distinct row count in the original source for the given groupKey, ignoring any filtering being applied by the expression.

Methods inherited from interface org.apache.calcite.rel.metadata.Metadata

rel

Field Detail

DEF

static final MetadataDef<BuiltInMetadata.PopulationSize> DEF

Method Detail

getPopulationSize

@Nullable Double getPopulationSize(ImmutableBitSet groupKey)

Estimates the distinct row count in the original source for the given groupKey, ignoring any filtering being applied by the expression. Typically, "original source" means base table, but for derived columns, the estimate may come from a non-leaf rel such as a LogicalProject.

Parameters:

groupKey - column mask representing the subset of columns for which the row count will be determined

Returns:

distinct row count for the given groupKey, or null if no reliable estimate can be determined