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fix: Fix incorrect lazy schema for explode() in agg() #19623

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fix: Fix incorrect lazy schema for explode() in agg() #19623

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27f269a
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nameexhaustion Nov 4, 2024
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2 changes: 1 addition & 1 deletion crates/polars-expr/src/expressions/apply.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -170,7 +170,7 @@ impl ApplyExpr {
// })?
let out: ListChunked = POOL.install(|| iter.collect::<PolarsResult<_>>())?;

debug_assert_eq!(out.dtype(), &DataType::List(Box::new(dtype)));
debug_assert_eq!(&dtype, out.dtype());
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I think the output field of the expression should created in an aggregation-context-aware manner, so I've updated this assertion.


out
} else {
Expand Down
28 changes: 20 additions & 8 deletions crates/polars-expr/src/planner.rs
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Expand Up @@ -239,7 +239,7 @@ fn create_physical_expr_inner(
// TODO! Order by
let group_by = create_physical_expressions_from_nodes(
partition_by,
Context::Default,
Context::Aggregation,
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This is under AExpr::Window

expr_arena,
schema,
state,
Expand Down Expand Up @@ -473,10 +473,13 @@ fn create_physical_expr_inner(
options,
} => {
let is_scalar = is_scalar_ae(expression, expr_arena);
let output_dtype =
let mut output_field =
expr_arena
.get(expression)
.to_field(schema, Context::Default, expr_arena)?;
if let Context::Aggregation = ctxt {
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I think we should just pass the context to line 497 instead of updating the dtype here.

output_field.dtype = DataType::List(Box::new(output_field.dtype));
}

let is_reducing_aggregation = options.flags.contains(FunctionFlags::RETURNS_SCALAR)
&& matches!(options.collect_groups, ApplyOptions::GroupWise);
Expand All @@ -501,21 +504,24 @@ fn create_physical_expr_inner(
*options,
state.allow_threading,
schema.clone(),
output_dtype,
output_field,
is_scalar,
)))
},
Function {
input,
function,
options,
..
} => {
let is_scalar = is_scalar_ae(expression, expr_arena);
let output_field =
let mut output_field =
expr_arena
.get(expression)
.to_field(schema, Context::Default, expr_arena)?;
if let Context::Aggregation = ctxt {
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idem

output_field.dtype = DataType::List(Box::new(output_field.dtype));
}

let is_reducing_aggregation = options.flags.contains(FunctionFlags::RETURNS_SCALAR)
&& matches!(options.collect_groups, ApplyOptions::GroupWise);
// Will be reset in the function so get that here.
Expand Down Expand Up @@ -565,9 +571,15 @@ fn create_physical_expr_inner(
move |c: &mut [polars_core::frame::column::Column]| c[0].explode().map(Some),
) as Arc<dyn ColumnsUdf>);

let field = expr_arena
.get(expression)
.to_field(schema, ctxt, expr_arena)?;
let mut field =
expr_arena
.get(expression)
.to_field(schema, Context::Default, expr_arena)?;

if let Context::Aggregation = ctxt {
field.dtype = DataType::List(Box::new(field.dtype));
}

Ok(Arc::new(ApplyExpr::new(
vec![input],
function,
Expand Down
1 change: 0 additions & 1 deletion crates/polars-plan/src/plans/aexpr/schema.rs
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Expand Up @@ -72,7 +72,6 @@ impl AExpr {
},
Explode(expr) => {
let field = arena.get(*expr).to_field_impl(schema, arena, nested)?;
*nested = nested.saturating_sub(1);
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Fix for the linked issue explode()


if let List(inner) = field.dtype() {
Ok(Field::new(field.name().clone(), *inner.clone()))
Expand Down
8 changes: 8 additions & 0 deletions py-polars/tests/unit/lazyframe/test_lazyframe.py
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Expand Up @@ -1424,3 +1424,11 @@ def test_lf_unnest() -> None:
]
)
assert_frame_equal(lf.unnest("a", "b").collect(), expected)


def test_lf_schema_explode_in_agg_19562() -> None:
lf = pl.LazyFrame({"a": 1, "b": [[1]]})
q = lf.group_by("a").agg(pl.col("b").explode())

assert q.collect_schema() == {"a": pl.Int32, "b": pl.List(pl.Int64)}
assert_frame_equal(q.collect(), pl.DataFrame({"a": 1, "b": [[1]]}))