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Fix: unnest with alias reports error #16854

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Fix: unnest with alias reports error #16854

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17 changes: 13 additions & 4 deletions datafusion/expr/src/logical_plan/builder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2090,10 +2090,19 @@ pub fn unnest(input: LogicalPlan, columns: Vec<Column>) -> Result<LogicalPlan> {
pub fn get_struct_unnested_columns(
col_name: &String,
inner_fields: &Fields,
) -> Vec<Column> {
alias: Option<&String>,
) -> Vec<Expr> {
inner_fields
.iter()
.map(|f| Column::from_name(format!("{}.{}", col_name, f.name())))
.map(|f| {
let col =
Expr::Column(Column::from_name(format!("{}.{}", col_name, f.name())));
if let Some(alias_name) = alias {
col.alias(format!("{alias_name}.{}", f.name()))
} else {
col
}
})
.collect()
}

Expand Down Expand Up @@ -2660,12 +2669,12 @@ mod tests {

assert_snapshot!(plan, @r"
Union
Cross Join:
Cross Join:
SubqueryAlias: left
Values: (Int32(1))
SubqueryAlias: right
Values: (Int32(1))
Cross Join:
Cross Join:
SubqueryAlias: left
Values: (Int32(1))
SubqueryAlias: right
Expand Down
21 changes: 14 additions & 7 deletions datafusion/sql/src/utils.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -415,6 +415,12 @@ impl RecursiveUnnestRewriter<'_> {

match data_type {
DataType::Struct(inner_fields) => {
let mut alias_name = None;
if let Expr::Alias(Alias { name, .. }) = self.root_expr {
alias_name = Some(name);
}

dbg!(alias_name.clone());
if !struct_allowed {
return internal_err!("unnest on struct can only be applied at the root level of select expression");
}
Expand All @@ -424,12 +430,11 @@ impl RecursiveUnnestRewriter<'_> {
);
self.columns_unnestings
.insert(Column::from_name(placeholder_name.clone()), None);
Ok(
get_struct_unnested_columns(&placeholder_name, &inner_fields)
.into_iter()
.map(Expr::Column)
.collect(),
)
Ok(get_struct_unnested_columns(
&placeholder_name,
&inner_fields,
alias_name,
))
}
DataType::List(_)
| DataType::FixedSizeList(_, _)
Expand Down Expand Up @@ -554,7 +559,9 @@ impl TreeNodeRewriter for RecursiveUnnestRewriter<'_> {
// instead of unnest(struct_arr_col, depth = 2)

let unnest_recursion = unnest_stack.len();
let struct_allowed = (&expr == self.root_expr) && unnest_recursion == 1;
let struct_allowed = ((&expr == self.root_expr)
|| (matches!(self.root_expr, Expr::Alias(Alias { expr: inner, .. }) if inner.as_ref() == &expr)))
&& unnest_recursion == 1;

let mut transformed_exprs = self.transform(
unnest_recursion,
Expand Down
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