BuiltInMetadata.PopulationSize (Apache Calcite API)

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.

Nested Class Summary

Nested Classes
Modifier and Type Interface Description

static interface BuiltInMetadata.PopulationSize.Handler
Handler API.

Field Summary

Fields
Modifier and Type Field Description

static MetadataDef<BuiltInMetadata.PopulationSize> DEF

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method	Description
`java.lang.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

- Field Detail
  - DEF
```
static final MetadataDef<BuiltInMetadata.PopulationSize> DEF
```
- Method Detail
  - getPopulationSize
```
java.lang.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