gruuya opened a new issue, #13481:
URL: https://github.com/apache/datafusion/issues/13481
### Describe the bug
It seems `SimplifyExpressions` will sometimes omit a cast which was
introduced by the `TypeCoercion` analyzer rule, leading to a loss in the
precision of the output DataType.[](url)
### To Reproduce
Run
```rust
#[test]
fn test_simplify_case_cast_list() {
use datafusion_functions_nested::expr_fn::make_array;
let element_field = Arc::new(Field::new("element", DataType::Int32,
true));
let expr = case(col("condition"))
.when(
lit(false),
cast(
make_array(vec![lit(2), lit(3)]),
DataType::List(element_field.clone()),
),
)
.otherwise(col("items"))
.unwrap()
.alias("items");
let expected = case(col("condition"))
.when(
lit(false),
cast(
lit(ScalarValue::List(ScalarValue::new_list_nullable(
&[ScalarValue::Int32(Some(2)),
ScalarValue::Int32(Some(3))],
&DataType::Int32,
))),
DataType::List(element_field),
),
)
.otherwise(col("items"))
.unwrap()
.alias("items");
assert_eq!(simplify(expr), expected);
}
```
It will fail because the cast clause gets (unexpectedly) stripped
```rust
assertion `left == right` failed
left: Alias(Alias { expr: Case(Case { expr: Some(Column(Column { relation:
None, name: "condition" })), when_then_expr: [(Literal(Boolean(false)),
Literal(List([2, 3])))], else_expr: Some(Column(Column { relation: None, name:
"items" })) }), relation: None, name: "items" })
right: Alias(Alias { expr: Case(Case { expr: Some(Column(Column { relation:
None, name: "condition" })), when_then_expr: [(Literal(Boolean(false)),
Cast(Cast { expr: Literal(List([2, 3])), data_type: List(Field { name:
"element", data_type: Int32, nullable: true, dict_id: 0, dict_is_ordered:
false, metadata: {} }) }))], else_expr: Some(Column(Column { relation: None,
name: "items" })) }), relation: None, name: "items" })
```
## Effects
I believe this in turn causes https://github.com/delta-io/delta-rs/pull/2886.
Basically `TypeCoercion` injects the CAST, while `SimplifyExpressions` omits
it. Consequently `OptimizeProjections` folds the two projections, but the
schema is computed from the outermost projection expressions, which now lack
the proper type info (i.e. the non-standard list item field names).
Minimal repro:
```rust
#[tokio::test]
async fn test_list_item() -> Result<()> {
use datafusion_functions_nested::expr_fn::make_array;
let element_field = Arc::new(Field::new("element", DataType::Int32,
true));
let items_field = Field::new(
"items",
DataType::List(element_field.clone()),
true,
);
let schema = Schema::new(vec![items_field.clone()]);
let mut items_builder =
ListBuilder::new(Int32Builder::new()).with_field(element_field.clone());
items_builder.append_value([Some(1)]);
let batch = RecordBatch::try_new(Arc::new(schema),
vec![Arc::new(items_builder.finish())])?;
let ctx = SessionContext::new();
let df = ctx.read_batch(batch).expect("source DataFrame")
.with_column("condition", lit(false))?
.select(vec![case(col("condition")).when(lit(false),
make_array(vec![lit(2), lit(3)])).otherwise(col("items"))?.alias("items")])?;
let _ = df.create_physical_plan().await?;
Ok(())
}
```
Fails with `Error: Context("Optimizer rule 'optimize_projections' failed",
Context("optimize_projections", Internal("Failed due to a difference in
schemas, original schema: DFSchema { inner: Schema { fields: [Field { name:
\"items\", data_type: List(Field { name: \"element\", data_type: Int32,
nullable: true, dict_id: 0, dict_is_ordered: false, metadata: {} }), nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {} }], metadata: {} },
field_qualifiers: [None], functional_dependencies: FunctionalDependencies {
deps: [] } }, new schema: DFSchema { inner: Schema { fields: [Field { name:
\"items\", data_type: List(Field { name: \"item\", data_type: Int32, nullable:
true, dict_id: 0, dict_is_ordered: false, metadata: {} }), nullable: true,
dict_id: 0, dict_is_ordered: false, metadata: {} }], metadata: {} },
field_qualifiers: [None], functional_dependencies: FunctionalDependencies {
deps: [] } }")))`
### Expected behavior
`SimplifyExpressions`should retain the CAST, and the should be no optimizer
errors in the second (high-level) example.
### Additional context
_No response_
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