Package org.apache.calcite.rel.metadata

Interface BuiltInMetadata.ColumnUniqueness

All Superinterfaces:

Metadata

Enclosing class:

BuiltInMetadata

public static interface BuiltInMetadata.ColumnUniqueness
extends Metadata

Metadata about whether a set of columns uniquely identifies a row.

Nested Class Summary

Nested Classes

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

Field Summary

Fields

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

Method Summary

Modifier and Type	Method	Description
Boolean	areColumnsUnique(ImmutableBitSet columns, boolean ignoreNulls)	Determines whether a specified set of columns from a specified relational expression are unique.

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

rel

Field Details

DEF

static final MetadataDef<BuiltInMetadata.ColumnUniqueness> DEF

Method Details

areColumnsUnique

Boolean areColumnsUnique(ImmutableBitSet columns,
 boolean ignoreNulls)

Determines whether a specified set of columns from a specified relational expression are unique.

For example, if the relational expression is a TableScan to T(A, B, C, D) whose key is (A, B), then:

• areColumnsUnique([0, 1]) yields true,
• areColumnsUnique([0]) yields false,
• areColumnsUnique([0, 2]) yields false.

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

Parameters:

columns - column mask representing the subset of columns for which uniqueness will be determined

ignoreNulls - if true, ignore null values when determining column uniqueness

Returns:

whether the columns are unique, or null if not enough information is available to make that determination