BuiltInMetadata.UniqueKeys (Apache Calcite API)

All Superinterfaces:

Metadata

All Known Subinterfaces:

BuiltInMetadata.All

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 MetadataDef<BuiltInMetadata.UniqueKeys> DEF

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.util.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 Detail
  - DEF
```
static final MetadataDef<BuiltInMetadata.UniqueKeys> DEF
```
- Method Detail
  - getUniqueKeys
```
java.util.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.
    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)