Core: Add a read-only Mumbling bitmap implementation#16747
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rdblue
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Jun 9, 2026
| httpcomponents-httpclient5 = { module = "org.apache.httpcomponents.client5:httpclient5", version.ref = "httpcomponents-httpclient5" } | ||
| immutables-value = { module = "org.immutables:value", version.ref = "immutables-value" } | ||
| jackson-bom = { module = "com.fasterxml.jackson:jackson-bom", version.ref = "jackson-bom" } | ||
| javafastpfor = { module = "me.lemire.integercompression:JavaFastPFOR", version.ref = "javafastpfor" } |
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This is for the benchmark and doesn't need to be included in the committed version.
rdblue
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Jun 9, 2026
| this.cardinality = | ||
| (data.get(data.position() + 1) & 0xFF) | ||
| | ((data.get(data.position() + 2) & 0xFF) << 8) | ||
| | ((data.get(data.position() + 3) & 0xFF) << 16); |
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This and other direct reads will be refactored to use utils in ByteBuffers after #16748 moves them out of VariantUtil.
pvary
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Jun 10, 2026
| Random random = new Random(1938745); | ||
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| // 256-value descriptor-like data: mostly [0,31] with ~5% [0,255] outliers | ||
| descriptorValues = PFORRandomData.exceptions(random, 256, 0.5f); |
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What pattern should I test? |
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This is a simple implementation of Mumbling bitmap that has been proposed for embedded bitmaps in v4 metadata.
This implementation includes 3 main classes:
BitPacking: bit packing and unpacking implementations for specific widths (1-7) used for descriptor encodingPFOREncoding: patched frame-of-reference encoding and decoding for descriptor bytesSupport for creating and modifying bitmaps will be added in later PRs, similar to the approach for variant where
SerializedValueimplementations were added first as a building block for mutable implementations.This also includes a benchmark to compare the PFOR implementation to JavaFastPFOR. This is not a fair comparison because JavaFastPFOR is intended for large arrays and vectorization, but the use cases tested are very small arrays that don't benefit from vectorization and have high overhead. The reason for the benchmark is to show that it doesn't make sense to delegate to JavaFastPFOR for a small descriptor array. This benchmark probably won't be committed as it is now in the final version, but I wanted to make it available for reviewers.
Co-Authored-By: Claude Code (Opus 4.7, 1M context) noreply@anthropic.com