Package org.apache.iceberg.transforms

Interface Transform<S,​T>

  • Type Parameters:
    S - Java class of source values
    T - Java class of transformed values
    All Superinterfaces:
    java.io.Serializable
    All Known Implementing Classes:
    UnknownTransform
    public interface Transform<S,​T>
extends java.io.Serializable
    A transform function used for partitioning.

    Implementations of this interface can be used to transform values, check or types, and project predicates to predicates on partition values.

    • Method Detail

      • apply

        T apply​(S value)
        Transforms a value to its corresponding partition value.
        Parameters:
        value - a source value
        Returns:
        a transformed partition value

      • canTransform

        boolean canTransform​(Type type)
        Checks whether this function can be applied to the given Type.
        Parameters:
        type - a type
        Returns:
        true if this transform can be applied to the type, false otherwise

      • getResultType

        Type getResultType​(Type sourceType)
        Returns the Type produced by this transform given a source type.
        Parameters:
        sourceType - a type
        Returns:
        the result type created by the apply method for the given type

      • project

        UnboundPredicate<T> project​(java.lang.String name,
                            BoundPredicate<S> predicate)
        Transforms a predicate to an inclusive predicate on the partition values produced by apply(Object).

        This inclusive transform guarantees that if pred(v) is true, then projected(apply(v)) is true.

        Parameters:
        name - the field name for partition values
        predicate - a predicate for source values
        Returns:
        an inclusive predicate on partition values

      • projectStrict

        UnboundPredicate<T> projectStrict​(java.lang.String name,
                                  BoundPredicate<S> predicate)
        Transforms a predicate to a strict predicate on the partition values produced by apply(Object).

        This strict transform guarantees that if strict(apply(v)) is true, then pred(v) is also true.

        Parameters:
        name - the field name for partition values
        predicate - a predicate for source values
        Returns:
        an inclusive predicate on partition values

      • isIdentity

        default boolean isIdentity()
        Return whether this transform is the identity transform.
        Returns:
        true if this is an identity transform, false otherwise

      • toHumanString

        default java.lang.String toHumanString​(T value)
        Returns a human-readable String representation of a transformed value.

        null values will return "null"

        Parameters:
        value - a transformed value
        Returns:
        a human-readable String representation of the value