feat: Complete ReservoirItemsUnion implementation #104
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…ternal logic - Add helper methods to ReservoirItemsSketch: GetImplicitSampleWeight, Copy, DownsampledCopy, getValueAtPosition, insertValueAtPosition, forceIncrementItemsSeen - Rewrite ReservoirItemsUnion.UpdateSketch with correct merge logic: - Downsample input if K > maxK - createNewGadget preserves source K in sampling mode - twoWayMergeInternal with 4 cases (exact/weighted, with swap) - Correct probability formula P = (K * w) / targetTotal - Create dedicated reservoir_items_union_test.go with Java-aligned tests - Move union tests from reservoir_items_sketch_test.go
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Jan 19, 2026
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Jan 20, 2026
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Can you add test cases?
- Compatibility test with java.
- sketches generation test.
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Added cross-language coverage for reservoir unions (long/double/string): tests now load 27 Java-generated files (empty, exact 1/10/32/100/128, sampling maxK 32/64/128) and we also generate matching Go fixtures; |
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Summary
This PR completes the ReservoirItemsUnion implementation to align with Java's functionality.
Changes
Core Logic Fixes
Fixed
twoWayMergeInternalto correctly handle 4 merge casesAdded
DownsampledCopy,Copy,GetImplicitSampleWeightmethodsAdded internal helpers:
getValueAtPosition,insertValueAtPosition,forceIncrementItemsSeenSerialization:
ToSlice()andNewReservoirItemsUnionFromSlice()UpdateFromRaw: Create sketch from raw components (n, k, items)
String(): Human-readable summaryTests
Serialization Format
Compatible with Java V2:
PS: Only V2 serialization is supported (V1 is legacy format from pre-2017).
Ref #103