Fix conditional outer join root predicates [databricks]

[nartal1]

Fixes #16067.

Description

Conditional right outer joins can fail with The expression must produce a boolean output, while conditional full outer joins can return incorrect results when the remaining condition is a root GpuBoundReference.

For BuildLeft, LazyCompiledCondition reorders the AST inputs but previously remapped only child expressions, leaving a root reference bound to the wrong column. This change remaps the root reference before recursively transforming its children.

CPU/GPU regression tests cover right and full outer joins with the AUTO, HASH_ONLY, and INNER_SORT_WITH_POST strategies.

Performance testing is not required because this changes only one-time AST condition rebinding and adds no row or batch hot-path work.

AI assistance disclosure: Codex assisted with issue implementation and validation. It was reviewed by the author before publication.

Checklists

Documentation

• Updated for new or modified user-facing features or behaviors
• No user-facing change

Testing

• Added or modified tests to cover new code paths
• Covered by existing tests
  (Please provide the names of the existing tests in the PR description.)
• Not required

Performance

• Tests ran and results are added in the PR description
• Issue filed with a link in the PR description
• Not required

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; no actionable correctness, security, test-quality, or performance issue remains.

Summary

This PR fixes BuildLeft conditional-join AST rebinding by remapping a root GpuBoundReference before recursively transforming child expressions.

• Preserves the established left ++ right to right ++ left ordinal mapping.
• Adds CPU/GPU parity coverage for conditional right and full outer joins.
• Exercises AUTO, HASH_ONLY, and INNER_SORT_WITH_POST strategies while requiring the intended GPU join operators.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A[Condition bound to left then right columns] --> B{Build side}
  B -->|BuildRight| C[Compile with left columns first]
  B -->|BuildLeft| D[Remap every bound reference including root]
  D --> E[Compile with right columns first]
  C --> F[Cached compiled AST]
  E --> F
  F --> G[Conditional GPU join]

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_{Reviews (1) · Last reviewed commit: "Fix root join condition rebinding"}

[nartal1]

build

[nartal1]

build

[gerashegalov]

LGTM

[sameerz]

build