Fix column-to-column comparison in WHERE clause

[spapin]

Summary

Fixes #10600

The PredicateComparisonRewriter previously rewrote column-to-column comparisons like WHERE a = b into minus(a, b) = 0. This arithmetic rewrite forced DOUBLE coercion on both operands, which:

• Broke string comparisons entirely — Double.parseDouble("some string") throws NumberFormatException
• Lost precision for integer types — large LONG values cast to DOUBLE can alias, making distinct values appear equal
• Affected both v1 and v2 engines — the v2 leaf stage applies the same rewriter, so even multi-stage queries hit this bug

The fix replaces the minus() rewrite with the type-safe comparison transform functions (equals, not_equals, greater_than, etc.) that already exist in BinaryOperatorTransformFunction. These dispatch on the actual stored types of both operands — Integer.compare for INT, Long.compare for LONG, String.compareTo for STRING — with no forced coercion.

Why the rewrite is still needed

The v1 filter engine requires a literal on the RHS of predicates. The rewrite moves the column-to-column comparison into a transform function, leaving a literal true on the RHS:

Before (broken):  EQUALS(json_extract_scalar(...), other_col)          ← column on RHS, v1 can't evaluate
Old rewrite:      EQUALS(minus(json_extract_scalar(...), other_col), 0) ← forced DOUBLE coercion, breaks strings
New rewrite:      EQUALS(equals(json_extract_scalar(...), other_col), true) ← type-safe per-row comparison

Related issues

• Server query with <column> = <column> for string column throws number format exception #10600: WHERE string_col = string_col throws NumberFormatException (open since Apr 2023)

Changes

• PredicateComparisonRewriter.java — a op b → EQUALS(comparison_func(a, b), true) instead of EQUALS(minus(a, b), 0)
• PredicateComparisonRewriterTest.java — covers all 6 comparison operators, function-on-LHS, operand preservation, and BETWEEN rejection
• JsonExtractScalarTest.java — end-to-end integration tests for string and numeric column-to-column comparisons via json_extract_scalar

Test plan

• PredicateComparisonRewriterTest — verifies rewrite structure for =, !=, <, >, >= and function-on-LHS
• JsonExtractScalarTest#testJsonExtractScalarComparedToColumn — end-to-end across all 7 JSON column variants:
  • String = (no match → empty result, no error)
  • String = same expression both sides (all rows match)
  • String != (all rows satisfy)
  • Numeric = (no match → empty result, no error)
  • Numeric > (all rows satisfy)
• Local quickstart: verified json_extract_scalar(properties, '$.hs_name', 'STRING', '') = expectedName returns correct matching rows

[codecov-commenter]

Codecov Report

❌ Patch coverage is 46.15385% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 36.83%. Comparing base (a6463d4) to head (3d1c402).
⚠️ Report is 18 commits behind head on master.

Files with missing lines	Patch %	Lines
.../parsers/rewriter/PredicateComparisonRewriter.java	46.15%	6 Missing and 1 partial ⚠️

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HEAD has 4 uploads less than BASE

Flag	BASE (a6463d4)	HEAD (3d1c402)
java-21	5	4
unittests1	1	0
unittests	2	1
temurin	5	4

Additional details and impacted files

@@              Coverage Diff              @@
##             master   #18587       +/-   ##
=============================================
- Coverage     64.27%   36.83%   -27.45%     
+ Complexity     1137     1136        -1     
=============================================
  Files          3314     3335       +21     
  Lines        204064   205908     +1844     
  Branches      31760    32129      +369     
=============================================
- Hits         131165    75841    -55324     
- Misses        62373   123209    +60836     
+ Partials      10526     6858     -3668     

Flag	Coverage Δ
custom-integration1	100.00% <ø> (ø)
integration	100.00% <ø> (ø)
integration1	100.00% <ø> (ø)
integration2	0.00% <ø> (ø)
java-21	36.83% <46.15%> (-27.45%)	⬇️
temurin	36.83% <46.15%> (-27.45%)	⬇️
unittests	36.82% <46.15%> (-27.45%)	⬇️
unittests1	?
unittests2	36.82% <46.15%> (+1.28%)	⬆️

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[xiangfu0]

hmm I thought #10600 is already resolved... no?

[spapin]

hmm I thought #10600 is already resolved... no?

My understanding is that there was a fix in #10444 for comparing the same column.

WHERE columnA = columnA

This change also supports different columns

WHERE columnA = columnB

The ticket mentions the NumberFormatException which is rooted in the Minus operation that was previously used. Let me know if this was the wrong issue to tag.