GH-3516: Optimize DeltaByteArrayWriter and DeltaLengthByteArrayValuesWriter (+33-55% encodeDeltaByteArray)

[iemejia]

Summary

Resolves #3516.

Two related changes in the DELTA_BYTE_ARRAY write path:

1. DeltaLengthByteArrayValuesWriter: drop the unused LittleEndianDataOutputStream wrapper

The class wrapped its CapacityByteArrayOutputStream with a LittleEndianDataOutputStream that was only used by Binary.writeTo() — an extra layer of dispatch on every value that never used any LE-specific functionality (writeInt/writeLong/etc.). Binary.writeTo(arrayOut) works directly with the underlying stream.

Also adds a new overload:

public void writeBytes(byte[] data, int offset, int length) {
  lengthWriter.writeInteger(length);
  arrayOut.write(data, offset, length);
}

so callers that already have the raw bytes can avoid allocating a Binary wrapper.

2. DeltaByteArrayWriter: eliminate per-value Binary.slice() allocation in the suffix path

Tightens the suffixWriter field type from ValuesWriter to DeltaLengthByteArrayValuesWriter (it's always constructed as one) so the new raw-bytes overload is callable. The suffix call becomes:

suffixWriter.writeBytes(vb, i, vb.length - i);

instead of suffixWriter.writeBytes(v.slice(i, vb.length - i)), eliminating the ByteArraySliceBackedBinary allocation per value plus a layer of virtual dispatch.

Benchmark results

From BinaryEncodingBenchmark.encodeDeltaByteArray / encodeDeltaLengthByteArray (added in #3512):

Benchmark	Configuration	master	this PR	speedup
encodeDeltaByteArray	LOW card, len=10	0.1028 µs	0.0662 µs	1.55x
encodeDeltaByteArray	HIGH card, len=10	0.1704 µs	0.1124 µs	1.52x
encodeDeltaByteArray	LOW card, len=100	0.2079 µs	0.1678 µs	1.24x
encodeDeltaLengthByteArray	LOW card, len=10	0.0481 µs	0.0397 µs	1.21x
encodeDeltaLengthByteArray	LOW card, len=100	0.1503 µs	0.1374 µs	1.09x

Long-string cases are flat or trivial — the per-value allocation is amortized away when each value is hundreds of bytes.

How to reproduce

The JMH benchmarks cited above are being added to parquet-benchmarks in #3512. Once that lands, reproduce with:

./mvnw clean package -pl parquet-benchmarks -DskipTests \
    -Dspotless.check.skip=true -Drat.skip=true -Djapicmp.skip=true
java -jar parquet-benchmarks/target/parquet-benchmarks.jar \
    'BinaryEncodingBenchmark.encodeDeltaByteArray|BinaryEncodingBenchmark.encodeDeltaLengthByteArray' \
    -wi 5 -i 10 -f 3

Compare runs against master (baseline) and this branch (optimized).

Validation

• parquet-column: 573 tests pass
• Built with -Dspotless.check.skip=true -Drat.skip=true -Djapicmp.skip=true

User-facing changes

None. No public API change. No file format change.

The new DeltaLengthByteArrayValuesWriter.writeBytes(byte[], int, int) overload is added on top of the existing public API.

Closes #3516

Part of a small series of focused performance PRs from work in parquet-perf. Previous: #3494, #3496, #3500, #3504, #3506, #3510, #3514. Companion benchmarks contribution: #3512.