Package 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.

Nested Class Summary

Nested Classes

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

Field Summary

Fields

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

Method Summary

Modifier and Type	Method	Description
@Nullable 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

Field Details

DEF

static final MetadataDef<BuiltInMetadata.UniqueKeys> DEF

Method Details

getUniqueKeys

@Nullable 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 a unique key plus other columns is still unique. Therefore, all columns are unique in a table with a unique key consisting of the empty set, as is the case for zero-row and single-row tables. The converse is not true: a table with all columns unique does necessary have the empty set as a key - that is never true with multi-row tables.

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, and a set containing the empty set implies every column is unique)