Module org.apache.arrow.vector

Package org.apache.arrow.vector.dictionary

Class DictionaryEncoder

java.lang.Object

org.apache.arrow.vector.dictionary.DictionaryEncoder

public class DictionaryEncoder
extends Object

Encoder/decoder for Dictionary encoded ValueVector. Dictionary encoding produces an integer ValueVector. Each entry in the Vector is index into the dictionary which can hold values of any type.

Constructor Summary

Constructors

Constructor	Description
DictionaryEncoder(Dictionary dictionary, BufferAllocator allocator)	Construct an instance.
DictionaryEncoder(Dictionary dictionary, BufferAllocator allocator, ArrowBufHasher hasher)	Construct an instance.

Method Summary

Modifier and Type	Method	Description
ValueVector	decode(ValueVector indices)	Decodes a vector with the dictionary in this encoder.
static ValueVector	decode(ValueVector indices, Dictionary dictionary)	Decodes a dictionary encoded array using the provided dictionary.
static ValueVector	decode(ValueVector indices, Dictionary dictionary, BufferAllocator allocator)	Decodes a dictionary encoded array using the provided dictionary.
ValueVector	encode(ValueVector vector)	Encodes a vector with the built hash table in this encoder.
static ValueVector	encode(ValueVector vector, Dictionary dictionary)	Dictionary encodes a vector with a provided dictionary.
static ArrowType.Int	getIndexType(int valueCount)	Get the indexType according to the dictionary vector valueCount.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

DictionaryEncoder

public DictionaryEncoder(Dictionary dictionary,
 BufferAllocator allocator)

Construct an instance.

DictionaryEncoder

public DictionaryEncoder(Dictionary dictionary,
 BufferAllocator allocator,
 ArrowBufHasher hasher)

Construct an instance.

Method Details

encode

public static ValueVector encode(ValueVector vector,
 Dictionary dictionary)

Dictionary encodes a vector with a provided dictionary. The dictionary must contain all values in the vector.

Parameters:

vector - vector to encode

dictionary - dictionary used for encoding

Returns:

dictionary encoded vector

decode

public static ValueVector decode(ValueVector indices,
 Dictionary dictionary)

Decodes a dictionary encoded array using the provided dictionary.

Parameters:

indices - dictionary encoded values, must be int type

dictionary - dictionary used to decode the values

Returns:

vector with values restored from dictionary

decode

public static ValueVector decode(ValueVector indices,
 Dictionary dictionary,
 BufferAllocator allocator)

Decodes a dictionary encoded array using the provided dictionary.

Parameters:

indices - dictionary encoded values, must be int type

dictionary - dictionary used to decode the values

allocator - allocator the decoded values use

Returns:

vector with values restored from dictionary

getIndexType

public static ArrowType.Int getIndexType(int valueCount)

Get the indexType according to the dictionary vector valueCount.

Parameters:

valueCount - dictionary vector valueCount.

Returns:

index type.

encode

public ValueVector encode(ValueVector vector)

Encodes a vector with the built hash table in this encoder.

decode

public ValueVector decode(ValueVector indices)

Decodes a vector with the dictionary in this encoder.

decode(ValueVector, Dictionary, BufferAllocator) should be used instead if only decoding is required as it can avoid building the DictionaryHashTable which only makes sense when encoding.