findepi commented on code in PR #14356:
URL: https://github.com/apache/datafusion/pull/14356#discussion_r1934247452
##########
datafusion/expr/src/logical_plan/plan.rs:
##########
@@ -2645,6 +2643,106 @@ pub struct Union {
pub schema: DFSchemaRef,
}
+impl Union {
+ /// Constructs new Union instance deriving schema from inputs.
+ fn try_new(inputs: Vec<Arc<LogicalPlan>>) -> Result<Self> {
+ let schema = Self::derive_schema_from_inputs(&inputs, false)?;
+ Ok(Union { inputs, schema })
+ }
+
+ /// Constructs new Union instance deriving schema from inputs.
+ /// Inputs do not have to have matching types and produced schema will
+ /// take type from the first input.
+ pub fn try_new_with_loose_types(inputs: Vec<Arc<LogicalPlan>>) ->
Result<Self> {
+ let schema = Self::derive_schema_from_inputs(&inputs, true)?;
+ Ok(Union { inputs, schema })
+ }
+
+ /// Constructs new Union instance deriving schema from inputs.
+ ///
+ /// `loose_types` if true, inputs do not have to have matching types and
produced schema will
+ /// take type from the first input. TODO this is not necessarily
reasonable behavior.
+ fn derive_schema_from_inputs(
+ inputs: &[Arc<LogicalPlan>],
+ loose_types: bool,
+ ) -> Result<DFSchemaRef> {
+ if inputs.len() < 2 {
+ return plan_err!("UNION requires at least two inputs");
+ }
+ let first_schema = inputs[0].schema();
+ let fields_count = first_schema.fields().len();
+ for input in inputs {
Review Comment:
you're right. Given the check is inexpensive, i thought it's ok to do it,
but it's probably better to iter().skip(1). Added
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