org.apache.paimon.utils

Class Projection

java.lang.Object

org.apache.paimon.utils.Projection

public abstract class Projection
extends Object

Projection represents a list of (possibly nested) indexes that can be used to project data types. A row projection includes both reducing the accessible fields and reordering them.

Method Summary

Modifier and Type	Method and Description
abstract Projection	complement(int fieldsNumber) Complement this projection.
abstract Projection	difference(Projection other) Perform a difference of this Projection with another Projection.
static Projection	empty() Create an empty Projection, that is a projection that projects no fields, returning an empty DataType.
boolean	equals(Object o)
int	hashCode()
abstract boolean	isNested()
static Projection	of(int[] indexes) Create a Projection of the provided indexes.
static Projection	of(int[][] indexes) Create a Projection of the provided indexes.
<T> List<T>	project(List<T> list) Project list.
abstract RowType	project(RowType rowType)
<T> T[]	project(T[] array) Project array.
static Projection	range(int startInclusive, int endExclusive) Create a Projection of a field range.
abstract int[][]	toNestedIndexes() Convert this instance to a nested projection index paths.
String	toString()
abstract int[]	toTopLevelIndexes() Convert this instance to a projection of top level indexes.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Method Detail

project

public abstract RowType project(RowType rowType)

project

public <T> T[] project(T[] array)

Project array.

project

public <T> List<T> project(List<T> list)

Project list.

isNested

public abstract boolean isNested()

Returns:

true whether this projection is nested or not.

difference

public abstract Projection difference(Projection other)

Perform a difference of this Projection with another Projection. The result of this operation is a new Projection retaining the same ordering of this instance but with the indexes from other removed. For example:

 
 [4, 1, 0, 3, 2] - [4, 2] = [1, 0, 2]
 
 

Note how the index 3 in the minuend becomes 2 because it's rescaled to project correctly a InternalRow or arity 3.

Parameters:

other - the subtrahend

Throws:

IllegalArgumentException - when other is nested.

complement

public abstract Projection complement(int fieldsNumber)

Complement this projection. The returned projection is an ordered projection of fields from 0 to fieldsNumber except the indexes in this Projection. For example:

 
 [4, 2].complement(5) = [0, 1, 3]
 
 

Parameters:

fieldsNumber - the size of the universe

Throws:

IllegalStateException - if this projection is nested.

toTopLevelIndexes

public abstract int[] toTopLevelIndexes()

Convert this instance to a projection of top level indexes. The array represents the mapping of the fields of the original DataType. For example, [0, 2, 1] specifies to include in the following order the 1st field, the 3rd field and the 2nd field of the row.

Throws:

IllegalStateException - if this projection is nested.

toNestedIndexes

public abstract int[][] toNestedIndexes()

Convert this instance to a nested projection index paths. The array represents the mapping of the fields of the original DataType, including nested rows. For example, [[0, 2, 1], ...] specifies to include the 2nd field of the 3rd field of the 1st field in the top-level row.

empty

public static Projection empty()

Create an empty Projection, that is a projection that projects no fields, returning an empty DataType.

of

public static Projection of(int[] indexes)

Create a Projection of the provided indexes.

See Also:

toTopLevelIndexes()

of

public static Projection of(int[][] indexes)

Create a Projection of the provided indexes.

See Also:

toNestedIndexes()

range

public static Projection range(int startInclusive,
                               int endExclusive)

Create a Projection of a field range.

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object