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[WIP] CLI program to write ALP encode example parquet files #49154
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Co-authored-by: Dhirhan Kanesalingam <[email protected]>
Also ensure that no line exceeds 90 characters
This reverts commit e85658b42b5373ef7e54295b100d1f083d55dd8d.
Set up base to allow metadata to be before data
This will aloow for easy future extensibility
This commit changes the ALP page layout from grouped metadata to an offset-based interleaved layout: OLD (grouped metadata): [Header][AlpInfos...][ForInfos...][Data...] NEW (offset-based): [Header][Offsets...][Vector0][Vector1]... where each Vector = [AlpInfo|ForInfo|Data] Benefits: - O(1) random access to any vector (previously O(n) to compute offsets) - Better locality for single-vector decompression - Enables parallel decompression without coordination - Storage overhead: 4 bytes per vector (~0.4% for typical pages) Changes: - alp_constants.h: Add OffsetType (uint32_t) for vector offsets - alp_wrapper.cc: EncodeAlp writes offsets + interleaved vectors - alp_wrapper.cc: DecodeAlp reads offsets and jumps directly to vectors - alp_wrapper.cc: GetMaxCompressedSize accounts for offset storage - alp_test.cc: Fix duplicate test name (EmptyInput -> EmptyInputViaCompression)
Update specification and code comments to document the new page layout: - alp.h: Updated AlpEncodedVector class documentation - ALP_Encoding_Specification.md: Updated page layout diagrams and descriptions
Add the ability to pre-compute sampling presets and reuse them for encoding. This is useful for: - Pre-computing presets outside benchmark loops (removes sampling overhead) - Reusing presets across multiple batches with similar data characteristics New public methods in AlpWrapper: - CreateSamplingPreset(): Samples input data and returns a preset - EncodeWithPreset(): Encodes using a pre-computed preset The existing Encode() method now delegates to these new methods internally. Also adds tests: - EncodeWithPreset: Verifies preset-based encoding produces identical output - PresetReuseAcrossBatches: Verifies preset can be reused for multiple encodes
- alp.h: Update serialization flow comment, AlpEncodedVectorView comments - alp.h: Mark AlpMetadataCache as LEGACY (not used with offset layout) - alp_wrapper.cc: Update AlpHeader page layout comment - ALP_Encoding_Specification.md: Fix vector size to be configurable - ALP_Encoding_Specification_terse.md: Complete rewrite for offset layout With the offset-based layout, AlpMetadataCache is no longer needed since the offset array provides O(1) random access directly.
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Component: C++
Component: Documentation
Component: Parquet
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This builds on the following PR from @prtkgaur
It contains a binary that creates files using the new ALP encoding here:
I don't intend to merge this PR, rather I plan to use it to create test parquet files, and am posting the PR in case anyone else is interested.
To build
To run
cd arrow/cpp ./build/release/parquet-write-parquet --encoding ALP /tmpThis writes a file like this to /tmp: single_f64_ALP.zip
TODO: make sure the following patterns, from the spec, are covered: