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.

Method Summary

Methods

Modifier and Type	Method and Description
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

Method Detail

getPopulationSize

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