gstvg commented on code in PR #21323:
URL: https://github.com/apache/datafusion/pull/21323#discussion_r3199619766
##########
datafusion/expr/src/higher_order_function.rs:
##########
@@ -224,35 +224,104 @@ pub struct LambdaArgument {
/// per outer sublist), avoiding the per-call `Schema::new` build that
/// includes constructing the internal name -> index map.
schema: SchemaRef,
+ /// A RecordBatch containing the captured columns inside this lambda body,
if any
+ ///
+ /// For example, for `array_transform([2], v -> v + a + b)`,
+ /// this will be a `RecordBatch` with two columns, `a` and `b`
+ captures: Option<RecordBatch>,
}
impl LambdaArgument {
- pub fn new(params: Vec<FieldRef>, body: Arc<dyn PhysicalExpr>) -> Self {
- let schema = Arc::new(Schema::new(params.clone()));
+ pub fn new(
+ params: Vec<FieldRef>,
+ body: Arc<dyn PhysicalExpr>,
+ captures: Option<RecordBatch>,
+ ) -> Self {
+ let fields = match &captures {
+ Some(batch) => batch
+ .schema_ref()
+ .fields()
+ .iter()
+ .cloned()
+ .chain(params.clone())
+ .collect(),
+ None => params.clone(),
+ };
+
+ let schema = Arc::new(Schema::new(fields));
+
Self {
params,
body,
schema,
+ captures,
}
}
/// Evaluate this lambda
/// `args` should evaluate to the value of each parameter
/// of the correspondent lambda returned in
[HigherOrderUDF::lambda_parameters].
+ ///
+ /// `adjust` should adjust the captured columns of this
+ /// lambda, if any, relative to it's parameters
Review Comment:
https://github.com/apache/datafusion/pull/21323/commits/2d1733354072c64a8b3f6d5aa63062ee704353c0
Added an example showing all variations: sublists with multiple values
(captured value repeated), empty sublist(captured value absent) and single
value sublist (captured value copied once). I have been working on this a long
time so it's hard for me to see it from the outside, if you think it's still
hard to understand, please do ask for improvements, thanks
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