Module compression 

Block compression for encoded column data (LZ4 and Zstd).

Each encoded column block can be optionally compressed after type-specific encoding. The compressed format prepends a codec tag and size header to enable deterministic decompression.

Compressed block format (v2)

[codec_tag: u8]              — 0x00=None, 0x01=Lz4, 0x02=Zstd
[compressed_size: u32]
[uncompressed_size: u32]
[compressed_data: compressed_size bytes]

When compressed_size == 0, the block is stored uncompressed. The codec tag enables deterministic dispatch — no trial decompression.

Constants

ZSTD_HIGH_LEVEL

Maximum Zstd compression level for cold-tier recompression.

Functions

compress_block

Compress a block using LZ4.

compress_block_with_codec

Compress a block using the specified compression codec.

compress_block_zstd

Compress a block using Zstd at a specific level.

compress_block_zstd_dict

Compress a block with a trained Zstd dictionary.

decompress_block

Decompress a block that was compressed with compress_block or compress_block_with_codec.

decompress_block_with_optional_dict

Decompress a block, optionally using a Zstd dictionary for CODEC_TAG_ZSTD_DICT blocks.

decompress_block_zstd_dict

Decompress a block that was compressed with a Zstd dictionary.

should_skip_compression

Returns true if the type-specific encoding already achieved enough compression that LZ4 should be skipped.

train_zstd_dictionary

Train a Zstd compression dictionary from a set of sample buffers.