fix(transform): floor nanosecond timestamps before bucket hashing - #2891
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fix(transform): floor nanosecond timestamps before bucket hashing#2891fallintoplace wants to merge 1 commit into
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Checked this against Java implementation and it does do the same. Thanks for the PR!
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| #[inline] | ||
| fn nanos_to_micros(v: i64) -> i64 { |
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| fn test_nanos_to_micros_uses_floor_division() { | ||
| assert_eq!(Bucket::nanos_to_micros(1_001), 1); | ||
| assert_eq!(Bucket::nanos_to_micros(1_000), 1); | ||
| assert_eq!(Bucket::nanos_to_micros(-1_000), -1); |
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Maybe worth a sanity check for 0, i64::Min and i64::Max
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Which issue does this PR close?
N/A. Found while comparing the Rust bucket transform with the Java reference implementation.
What changes are included in this PR?
Rust integer division truncates toward zero, while Iceberg Java converts nanoseconds to microseconds with floor division before bucket hashing. For negative values that are not exactly microsecond-aligned, dividing by 1,000 therefore hashed the wrong microsecond. For example,
-1,001 nsbecame-1 µsinstead of-2 µs, which could place pre-epoch values in a different partition bucket across implementations.This PR centralizes nanosecond-to-microsecond conversion with Euclidean division and uses it for:
Time64values with nanosecond precisionTimestampvalues with nanosecond precisiontimestamp_nsandtimestamptz_nsliteralsPositive and exactly microsecond-aligned values are unchanged.
Are these changes tested?
Yes. Unit tests assert the conversion directly for positive, aligned-negative, and unaligned-negative values, then verify that pre-epoch nanosecond literals and Arrow arrays bucket identically to their equivalent microsecond values.
Validated with:
cargo test -p iceberg transform::bucket::test --libcargo clippy -p iceberg --lib -- -D warnings