kosiew opened a new pull request, #21545:
URL: https://github.com/apache/datafusion/pull/21545
## Which issue does this PR close?
* Part of #20164
---
## Rationale for this change
Downstream components in DataFusion currently branch on both `CastExpr` and
`CastColumnExpr`, even though they represent equivalent semantics after recent
cast unification work. This duplication increases maintenance burden,
introduces unnecessary complexity, and raises the risk of inconsistent behavior
when evolving cast-related logic.
This PR simplifies downstream logic by collapsing these dual branches into a
single `CastExpr`-based handling path, aligning with the broader cast
unification effort.
---
## What changes are included in this PR?
* **Removed `CastColumnExpr` handling in downstream logic**:
* Eliminated branching specific to `CastColumnExpr` in:
* `equivalence/properties/mod.rs`
* `pruning/pruning_predicate.rs`
* **Unified cast substitution logic in ordering equivalence**:
* Replaced `substitute_cast_like_ordering` with `substitute_cast_ordering`
* Simplified implementation to only consider `CastExpr`
* Preserved correctness by ensuring:
* Exact child expression match
* Order-preserving (widening) casts only
* **Refactored pruning rewrite logic**:
* Introduced helper: `rewrite_cast_child_to_prunable`
* Removed duplicated validation and recursion logic across cast types
* Updated both `CastExpr` and `TryCastExpr` handling to reuse the helper
* **Test updates and cleanup**:
* Updated tests to use `CastExpr::new_with_target_field`
* Simplified test cases by removing vector-based equality conditions
* Removed obsolete test covering `CastColumnExpr`
* Renamed pruning test to reflect unified cast handling
* **Minor code cleanups**:
* Removed unused imports
* Simplified iterator chains and substitution logic
---
## Are these changes tested?
Yes.
* Existing pruning and equivalence tests were updated to reflect the unified
cast handling.
* Obsolete tests relying on `CastColumnExpr` were removed.
* Test cases were adjusted to ensure behavior remains unchanged, including:
* Ordering equivalence with cast substitutions
* Predicate pruning with cast expressions
These updates ensure no regression in behavior while validating the
simplified implementation.
---
## Are there any user-facing changes?
No.
This change is an internal refactor and does not modify user-facing APIs or
query behavior. It preserves existing semantics while improving maintainability.
---
## LLM-generated code disclosure
This PR includes LLM-generated code and comments. All LLM-generated content
has been manually reviewed and tested.
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