yyy1000 commented on code in PR #10494:
URL: https://github.com/apache/datafusion/pull/10494#discussion_r1600567694
##########
datafusion/optimizer/src/propagate_empty_relation.rs:
##########
@@ -154,14 +156,14 @@ impl OptimizerRule for PropagateEmptyRelation {
Ok(Transformed::yes(LogicalPlan::Projection(
Projection::new_from_schema(
Arc::new(child),
- plan.schema().clone(),
+ input_schema.clone(),
),
)))
}
} else {
Ok(Transformed::yes(LogicalPlan::Union(Union {
inputs: new_inputs,
- schema: union.schema.clone(),
+ schema: input_schema.clone(),
Review Comment:
Oh, I see. It seems true.
The current code will create the Union schema based on it's first input,
https://github.com/apache/datafusion/blob/1d4b808c6f46bead241166fb1ed4646b3d17b01d/datafusion/expr/src/logical_plan/builder.rs#L1375-L1400.
In the example, it's 'a', but later 'a' was removed, and the new input schema
field would be 'test'.
However I think this example may be a use case, based on the example a Union
has two Project plan as inputs, how to coerce them seems a question for me. 🥲
They already have different schemas and I can't know which one would be the
merged schema.
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