Misc improvements to ProjectionExprs #18719
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This PR adds trait implementations, a project_batch() method, and fixes a bug in update_expr() for literal expressions. Also adds comprehensive tests. Part of apache#18627
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Jefffrey
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Nov 17, 2025
Co-authored-by: Jeffrey Vo <[email protected]>
adriangb
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Nov 17, 2025
| /// | ||
| /// This function accepts a pre-computed output schema instead of calling [`ProjectionExprs::project_schema`] | ||
| /// so that repeated calls do not have schema projection overhead. | ||
| pub fn project_batch( |
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Maybe a better API than this would be make_projector() -> Projector where Projector holds a reference the output schema.
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Yep! I'm just thinking it would be less error prone to package it up in a struct. I'll push the change here then we can rebase #18627 to use the better version once this is merged.
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The point is that users don't have to track output_schema and pass it in, they can just keep track of a Projector
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I implemented my idea in f6afd71 and was able to use it to simplify ProjectionExec a bit so it's already used 😄
xudong963
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Jefffrey
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Nov 18, 2025
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## Summary This PR enhances the physical-expr projection handling with several improvements needed for better projection management in datasources. ## Changes 1. **Add trait implementations**: - Added `PartialEq` and `Eq` for `ProjectionExpr` - Added `PartialEq` and `Eq` for `ProjectionExprs` 2. **Add `project_batch()` method**: - Efficiently projects `RecordBatch` with pre-computed schema - Handles empty projections correctly - Reduces schema projection overhead for repeated calls 3. **Fix `update_expr()` bug**: - **Bug**: Previously returned `None` for literal expressions (no column references) - **Fix**: Now returns `Some(expr)` for both `Unchanged` and `RewrittenValid` states - **Impact**: Critical for queries like `SELECT 1 FROM table` where no file columns are needed 4. **Change `from_indices()` signature**: - Changed from `&SchemaRef` to `&Schema` for consistency 5. **Add comprehensive tests**: - `test_merge_empty_projection_with_literal()` - Reproduces roundtrip issue - `test_update_expr_with_literal()` - Tests literal handling - `test_update_expr_with_complex_literal_expr()` - Tests mixed expressions ## Part of This PR is part of apache#18627 - a larger effort to refactor projection handling in DataFusion. ## Testing All tests pass: - ✅ New projection tests - ✅ Existing physical-expr test suite - ✅ Doc tests ## AI use I asked Claude to extract this change from apache#18627 --------- Co-authored-by: Jeffrey Vo <[email protected]>
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Summary
This PR enhances the physical-expr projection handling with several improvements needed for better projection management in datasources.
Changes
Add trait implementations:
PartialEqandEqforProjectionExprPartialEqandEqforProjectionExprsAdd
project_batch()method:RecordBatchwith pre-computed schemaFix
update_expr()bug:Nonefor literal expressions (no column references)Some(expr)for bothUnchangedandRewrittenValidstatesSELECT 1 FROM tablewhere no file columns are neededChange
from_indices()signature:&SchemaRefto&Schemafor consistencyAdd comprehensive tests:
test_merge_empty_projection_with_literal()- Reproduces roundtrip issuetest_update_expr_with_literal()- Tests literal handlingtest_update_expr_with_complex_literal_expr()- Tests mixed expressionsPart of
This PR is part of #18627 - a larger effort to refactor projection handling in DataFusion.
Testing
All tests pass:
AI use
I asked Claude to extract this change from #18627