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GH-3522: Reuse intermediate buffers in RunLengthBitPackingHybridDecoder PACKED path (~22% throughput on dictionary-id decode) #3523

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GH-3522: Reuse intermediate buffers in RunLengthBitPackingHybridDecoder PACKED path (~22% throughput on dictionary-id decode) #3523

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22 changes: 17 additions & 5 deletions .../src/main/java/org/apache/parquet/column/values/rle/RunLengthBitPackingHybridDecoder.java
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Original file line number Diff line number Diff line change
Expand Up @@ -48,6 +48,11 @@ private static enum MODE {
private int currentCount;
private int currentValue;
private int[] currentBuffer;
private int currentBufferLength;

// Reusable buffers to avoid per-run allocation in PACKED mode
private int[] packedValuesBuffer = new int[0];
private byte[] packedBytesBuffer = new byte[0];

public RunLengthBitPackingHybridDecoder(int bitWidth, InputStream in) {
LOG.debug("decoding bitWidth {}", bitWidth);
Expand All @@ -69,7 +74,7 @@ public int readInt() throws IOException {
result = currentValue;
break;
case PACKED:
result = currentBuffer[currentBuffer.length - 1 - currentCount];
result = currentBuffer[currentBufferLength - 1 - currentCount];
break;
default:
throw new ParquetDecodingException("not a valid mode " + mode);
Expand All @@ -90,17 +95,24 @@ private void readNext() throws IOException {
case PACKED:
int numGroups = header >>> 1;
currentCount = numGroups * 8;
currentBufferLength = currentCount;
LOG.debug("reading {} values BIT PACKED", currentCount);
currentBuffer = new int[currentCount]; // TODO: reuse a buffer
byte[] bytes = new byte[numGroups * bitWidth];
if (packedValuesBuffer.length < currentCount) {
packedValuesBuffer = new int[currentCount];
}
currentBuffer = packedValuesBuffer;
int bytesRequired = numGroups * bitWidth;
if (packedBytesBuffer.length < bytesRequired) {
packedBytesBuffer = new byte[bytesRequired];
}
// At the end of the file RLE data though, there might not be that many bytes left.
int bytesToRead = (int) Math.ceil(currentCount * bitWidth / 8.0);
bytesToRead = Math.min(bytesToRead, in.available());
new DataInputStream(in).readFully(bytes, 0, bytesToRead);
new DataInputStream(in).readFully(packedBytesBuffer, 0, bytesToRead);
for (int valueIndex = 0, byteIndex = 0;
valueIndex < currentCount;
valueIndex += 8, byteIndex += bitWidth) {
packer.unpack8Values(bytes, byteIndex, currentBuffer, valueIndex);
packer.unpack8Values(packedBytesBuffer, byteIndex, currentBuffer, valueIndex);
}
break;
default:
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