Optimize compression hot paths: bypass Hadoop codec abstraction for Snappy, LZ4_RAW, ZSTD, and GZIP

[iemejia]

Summary

Bypass the Hadoop Compressor/Decompressor/CodecPool abstraction layer in CodecFactory and DirectCodecFactory, calling native compression libraries directly. This eliminates per-page stream creation, intermediate buffer copies, and codec pool synchronization for all four supported codecs.

What changes

• Snappy: Replace CodecPool + SnappyCompressor (which copies heap→direct→heap) with a single Snappy.compress(byte[], byte[]) / Snappy.uncompress(byte[], byte[]) JNI call and a reusable output buffer.
• LZ4_RAW: Replace NonBlockedCompressor (which allocates direct ByteBuffers and copies heap↔direct twice per call) with heap ByteBuffer.wrap() and direct airlift LZ4 compress/decompress — zero intermediate copies.
• ZSTD: Replace ZstdCompressorStream with ZstdOutputStreamNoFinalizer (avoids finalizer registration) and cache the ZSTD level / buffer pool configuration reads per compressor instance instead of re-reading Configuration on each page.
• GZIP: Replace Hadoop's GzipCodec (which wraps Java's Deflater/Inflater in stream abstractions) with direct Deflater/Inflater usage, reusing instances via reset() and managing GZIP headers/trailers manually.
• Benchmark: Update CompressionBenchmark page sizes from {8KB, 64KB, 256KB} to {64KB, 128KB, 256KB, 1MB} to reflect real-world Parquet page sizes (most pages are 64-256KB due to the 20K row-count limit from PARQUET-1414; only wide string/binary columns hit the 1MB size limit).

Benchmark results (ops/s, higher is better)

Compression

Codec	Page Size	Master	Branch	Delta
SNAPPY	64 KB	53,979	60,799	+12.6%
SNAPPY	128 KB	27,764	30,524	+9.9%
SNAPPY	256 KB	13,549	14,648	+8.1%
SNAPPY	1 MB	2,445	2,675	+9.4%
LZ4_RAW	1 MB	1,961	2,191	+11.7%
LZ4_RAW	64-256 KB	—	—	within noise (-1 to -4%)
ZSTD	all sizes	—	—	within noise
GZIP	all sizes	—	—	within noise

Decompression

Codec	Page Size	Master	Branch	Delta
LZ4_RAW	64 KB	80,415	118,358	+47.2%
LZ4_RAW	128 KB	40,615	59,620	+46.8%
LZ4_RAW	256 KB	19,888	29,914	+50.4%
LZ4_RAW	1 MB	4,628	7,517	+62.4%
SNAPPY	64 KB	60,928	67,224	+10.3%
SNAPPY	128 KB	29,919	33,457	+11.8%
SNAPPY	256 KB	14,431	15,912	+10.3%
SNAPPY	1 MB	3,140	3,540	+12.7%
ZSTD	64 KB	32,042	35,750	+11.6%
ZSTD	128 KB	19,447	21,800	+12.1%
ZSTD	256 KB	9,495	10,759	+13.3%
ZSTD	1 MB	2,155	2,409	+11.8%
GZIP	128 KB	4,101	4,536	+10.6%
GZIP	256 KB	1,736	1,891	+8.9%
GZIP	1 MB	406	442	+9.1%

JMH config: JDK 25.0.3 Temurin, 1 fork, 2 warmup × 1s, 3 measurement × 2s.

Why LZ4_RAW decompression gains are largest

NonBlockedDecompressor performs two full data copies per operation — heap byte[] → direct ByteBuffer on input, direct ByteBuffer → heap byte[] on output — plus direct buffer allocation and synchronized access. The bypass eliminates both copies by using ByteBuffer.wrap() on heap arrays, letting airlift's LZ4 decompress directly between heap buffers.

Why ZSTD compression gains are minimal

ZstandardCodec already returns null from createCompressor()/createDecompressor() and delegates directly to zstd-jni streams. The Hadoop abstraction overhead was already bypassed at the codec level. The branch adds finalizer avoidance (NoFinalizer variants) and caches configuration reads, which helps decompression but leaves compression within noise.

Alternative considered: modify codecs instead of CodecFactory

We evaluated modifying SnappyCodec and Lz4RawCodec to follow the ZstandardCodec pattern (return null from createCompressor(), use custom stream wrappers). This approach was 25-50% slower than the CodecFactory bypass for Snappy/LZ4 and even 20-47% slower than master. The per-call stream creation, ByteArrayOutputStream buffering, and lack of buffer reuse dominate for memory-bandwidth-bound codecs where the actual compression takes only 8-65 microseconds.

Files changed

• CodecFactory.java: Bypass compressor/decompressor with codec-specific inner classes (SnappyBytesCompressor, Lz4RawBytesCompressor, ZstdBytesCompressor, GzipBytesCompressor + matching decompressors)
• DirectCodecFactory.java: Bypass for direct ByteBuffer path (Snappy, LZ4_RAW, ZSTD)
• BytesInput.java: Add ByteBufferBackedOutputStream to avoid toByteArray() copies
• CompressionBenchmark.java: Realistic page sizes + JMH annotation processor fix for Java 17+
• TestDirectCodecFactory.java: Updated tests for bypass path