org.apache.calcite.rel.metadata

Interface BuiltInMetadata.UniqueKeys

All Superinterfaces:

Metadata

Enclosing class:

BuiltInMetadata

public static interface BuiltInMetadata.UniqueKeys
extends Metadata

Metadata about which combinations of columns are unique identifiers.

Method Summary

Methods

Modifier and Type	Method and Description
Set<ImmutableBitSet>	getUniqueKeys(boolean ignoreNulls) Determines the set of unique minimal keys for this expression.

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

rel

Method Detail

getUniqueKeys

Set<ImmutableBitSet> getUniqueKeys(boolean ignoreNulls)

Determines the set of unique minimal keys for this expression. A key is represented as an ImmutableBitSet, where each bit position represents a 0-based output column ordinal.

Note that RelNode.isDistinct() should return true if and only if at least one key is known.

Nulls can be ignored if the relational expression has filtered out null values.

Parameters:

ignoreNulls - if true, ignore null values when determining whether the keys are unique

Returns:

set of keys, or null if this information cannot be determined (whereas empty set indicates definitely no keys at all)