apache / apache/datafusion

Type coercion should select cheapest cast.

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#5,928 0 comments 0 reactions 0 assignees View on GitHub
bug
Dominant language
Rust
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Forks
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Avg merge
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Merged PRs (30d)
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Description

### Describe the bug

a Expr like `col(a) > utf('8')`.
We shouldn't cast `col(a)`.

### To Reproduce

```rs
#[test]
fn between_infer_cheap_type() -> Result<()> {
let expr = Expr::Between(Between::new(
Box::new(col("a")),
false,
// (cast('2002-05-08' as date) + interval '1 months')
Box::new(Expr::BinaryExpr(BinaryExpr {
left: Box::new(Expr::Cast(Cast {
expr: Box::new(Expr::Literal(Utf8(Some("2002-05-08".to_string())))),
data_type: DataType::Date32,
})),
op: Operator::Plus,
right: Box::new(Expr::Literal(ScalarValue::IntervalYearMonth(Some(1)))),
})),
Box::new(Expr::Literal(Utf8(Some("2002-12-08".to_string())))),
));
let empty = empty_with_type(DataType::Utf8);
let plan = LogicalPlan::Filter(Filter::try_new(expr, empty)?);
// TODO
let expected =
"Filter: CAST(a AS Date32) BETWEEN CAST(Utf8(\"2002-05-08\") AS Date32) + IntervalYearMonth(\"1\") AND CAST(Utf8(\"2002-12-08\") AS Date32)\
\n EmptyRelation";
assert_analyzed_plan_eq(Arc::new(TypeCoercion::new()), &plan, expected)
}
```

### Expected behavior

_No response_

### Additional context

_No response_

Contributor guide

Open the contributing guide

Research direction

Start with the between_infer_cheap_type test in the issue and inspect the TypeCoercion analyzer used by assert_analyzed_plan_eq. Reproduce the current analyzed plan, then determine how the test should express choosing the cheapest cast for the comparison. Done means the analyzer and regression test agree with the intended plan without unnecessarily casting col(a).

Written by the indexing model from the issue text.

Assessment

Tech stack
rust
Domain
backend
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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