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GH-14873: [Java] DictionaryEncoder can decode without building a DictionaryHashTable #14874

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Merged
lidavidm merged 1 commit into from
Dec 8, 2022
Merged

GH-14873: [Java] DictionaryEncoder can decode without building a DictionaryHashTable #14874

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39 changes: 25 additions & 14 deletions java/vector/src/main/java/org/apache/arrow/vector/dictionary/DictionaryEncoder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -76,8 +76,30 @@ public static ValueVector encode(ValueVector vector, Dictionary dictionary) {
* @return vector with values restored from dictionary
*/
public static ValueVector decode(ValueVector indices, Dictionary dictionary) {
DictionaryEncoder encoder = new DictionaryEncoder(dictionary, indices.getAllocator());
return encoder.decode(indices);
return decode(indices, dictionary, indices.getAllocator());
}

/**
* Decodes a dictionary encoded array using the provided dictionary.
*
* @param indices dictionary encoded values, must be int type
* @param dictionary dictionary used to decode the values
* @param allocator allocator the decoded values use
* @return vector with values restored from dictionary
*/
public static ValueVector decode(ValueVector indices, Dictionary dictionary, BufferAllocator allocator) {
int count = indices.getValueCount();
ValueVector dictionaryVector = dictionary.getVector();
int dictionaryCount = dictionaryVector.getValueCount();
// copy the dictionary values into the decoded vector
TransferPair transfer = dictionaryVector.getTransferPair(allocator);
transfer.getTo().allocateNewSafe();

BaseIntVector baseIntVector = (BaseIntVector) indices;
retrieveIndexVector(baseIntVector, transfer, dictionaryCount, 0, count);
ValueVector decoded = transfer.getTo();
decoded.setValueCount(count);
return decoded;
}

/**
Expand Down Expand Up @@ -180,17 +202,6 @@ public ValueVector encode(ValueVector vector) {
* Decodes a vector with the built hash table in this encoder.
*/
public ValueVector decode(ValueVector indices) {
int count = indices.getValueCount();
ValueVector dictionaryVector = dictionary.getVector();
int dictionaryCount = dictionaryVector.getValueCount();
// copy the dictionary values into the decoded vector
TransferPair transfer = dictionaryVector.getTransferPair(allocator);
transfer.getTo().allocateNewSafe();

BaseIntVector baseIntVector = (BaseIntVector) indices;
retrieveIndexVector(baseIntVector, transfer, dictionaryCount, 0, count);
ValueVector decoded = transfer.getTo();
decoded.setValueCount(count);
return decoded;
return decode(indices, dictionary, allocator);
}
}