org.apache.arrow.algorithm.dictionary

Class SearchDictionaryEncoder<E extends BaseIntVector,D extends ValueVector>

java.lang.Object

org.apache.arrow.algorithm.dictionary.SearchDictionaryEncoder<E,D>

Type Parameters:

E - encoded vector type.

D - decoded vector type, which is also the dictionary type.

public class SearchDictionaryEncoder<E extends BaseIntVector,D extends ValueVector>
extends Object

Dictionary encoder based on searching.

Constructor Summary

Constructors

Constructor and Description
SearchDictionaryEncoder(D dictionary, VectorValueComparator<D> comparator) Constructs a dictionary encoder.
SearchDictionaryEncoder(D dictionary, VectorValueComparator<D> comparator, boolean encodeNull) Constructs a dictionary encoder.

Method Summary

Modifier and Type	Method and Description
void	encode(D input, E output) Encodes an input vector by binary search.

Methods inherited from class java.lang.Object

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

Constructor Detail

SearchDictionaryEncoder

public SearchDictionaryEncoder(D dictionary,
                               VectorValueComparator<D> comparator)

Constructs a dictionary encoder.

Parameters:

dictionary - the dictionary. It must be in sorted order.

comparator - the criteria for sorting.

SearchDictionaryEncoder

public SearchDictionaryEncoder(D dictionary,
                               VectorValueComparator<D> comparator,
                               boolean encodeNull)

Constructs a dictionary encoder.

Parameters:

dictionary - the dictionary. It must be in sorted order.

comparator - the criteria for sorting.

encodeNull - a flag indicating if null should be encoded. It determines the behaviors for processing null values in the input during encoding/decoding.

For encoding, when a null is encountered in the input, 1) If the flag is set to true, the encoder searches for the value in the dictionary, and outputs the index in the dictionary. 2) If the flag is set to false, the encoder simply produces a null in the output.

For decoding, when a null is encountered in the input, 1) If the flag is set to true, the decoder should never expect a null in the input. 2) If set to false, the decoder simply produces a null in the output.

Method Detail

encode

public void encode(D input,
                   E output)

Encodes an input vector by binary search. So the algorithm takes O(n * log(m)) time, where n is the length of the input vector, and m is the length of the dictionary.

Parameters:

input - the input vector.

output - the output vector. Note that it must be in a fresh state. At least, all its validity bits should be clear.