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 Summary

Modifier and Type	Method and Description
T	apply(S value) Transforms a value to its corresponding partition value.
boolean	canTransform(Type type) Checks whether this function can be applied to the given Type.
default java.lang.String	dedupName() Return the unique transform name to check if similar transforms for the same source field are added multiple times in partition spec builder.
Type	getResultType(Type sourceType) Returns the Type produced by this transform given a source type.
default boolean	isIdentity() Return whether this transform is the identity transform.
default boolean	preservesOrder() Whether the transform preserves the order of values (is monotonic).
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).
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).
default boolean	satisfiesOrderOf(Transform<?,?> other) Whether ordering by this transform's result satisfies the ordering of another transform's result.
default java.lang.String	toHumanString(T value) Returns a human-readable String representation of a transformed value.

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

preservesOrder

default boolean preservesOrder()

Whether the transform preserves the order of values (is monotonic).

A transform preserves order for values when for any given a and b, if a < b then apply(a) <= apply(b).

Returns:

true if the transform preserves the order of values

satisfiesOrderOf

default boolean satisfiesOrderOf(Transform<?,?> other)

Whether ordering by this transform's result satisfies the ordering of another transform's result.

For example, sorting by day(ts) will produce an ordering that is also by month(ts) or year(ts). However, sorting by day(ts) will not satisfy the order of hour(ts) or identity(ts).

Returns:

true if ordering by this transform is equivalent to ordering by the other transform

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

dedupName

default java.lang.String dedupName()

Return the unique transform name to check if similar transforms for the same source field are added multiple times in partition spec builder.

Returns:

a name used for dedup