- All Superinterfaces:
- Enclosing class:
public static interface BuiltInMetadata.DistinctRowCount extends Metadata
Metadata about the number of distinct rows returned by a set of columns in a relational expression.
Nested Class SummaryModifier and TypeInterfaceDescription
static interfaceHandler API.
Method SummaryModifier and TypeMethodDescription
@Nullable DoubleEstimates the number of rows which would be produced by a GROUP BY on the set of columns indicated by groupKey, where the input to the GROUP BY has been pre-filtered by predicate.
getDistinctRowCountEstimates the number of rows which would be produced by a GROUP BY on the set of columns indicated by groupKey, where the input to the GROUP BY has been pre-filtered by predicate. This quantity (leaving out predicate) is often referred to as cardinality (as in gender being a "low-cardinality column").
groupKey- column mask representing group by columns
predicate- pre-filtered predicates
- distinct row count for groupKey, filtered by predicate, or null if no reliable estimate can be determined