fix: treat -0.0 and +0.0 as equal in comparisons and IN list#22628
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sweb wants to merge 2 commits into
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fix: treat -0.0 and +0.0 as equal in comparisons and IN list#22628sweb wants to merge 2 commits into
sweb wants to merge 2 commits into
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Which issue does this PR close?
Rationale for this change
Per IEEE 754 default semantics,
-0.0 == +0.0(and-0.0 < +0.0is false). PostgreSQL, DuckDB, and Python all follow this. DataFusion currently treats-0.0as strictly less than+0.0because arrow-rs' comparison kernels intentionally use totalOrder semantics. This produces surprising results inWHEREfilters,INlists, andIS [NOT] DISTINCT FROM, especially when-0.0is produced by arithmetic on a column (e.g.x * -1wherex = 0.0).See also https://github.com/apache/arrow-rs/blob/58.3.0/arrow-ord/src/cmp.rs#L66-L80
This was debugged, replicated and further explored using Claude Code. However, the result was adjusted and further improved.
What changes are included in this PR?
normalize_neg_zero/normalize_neg_zero_array/normalize_neg_zero_scalarindatafusion-physical-expr-common::datum. These rewrite-0.0to+0.0for float inputs and pass arrays through unchanged (no allocation) when no-0.0is present.apply_cmpso all comparison operators (=,<>,<,<=,>,>=, distinct / not-distinct, like / ilike) inherit IEEE 754 zero semantics.InListExprfor both the dynamic comparator path and the per-list-expression normalization. For the primitive static filter (which hashes viaOrderedFloat), inserting0.0now also inserts-0.0(and vice versa) so set membership matches the normalized comparison semantics.Are these changes tested?
Yes:
datum.rscover float normalization and check for passthrough when no-0.0is there, also dictionaries.Are there any user-facing changes?
Yes, comparisons against
-0.0change with this.Since this introduces an extra step for comparisons, this also has performance implications - I tried to reduce this by checking for float first and it reduces the performance hit but I did not get very consistent benchmark results. Please check whether IEEE 754 behavior for
-0.0is desirable for DataFusion and whether this line of implementation fits.