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Optimize redundant calls to UDFs producing StructArray #23655
Description
Is your feature request related to a problem or challenge?
Since UDF can only return a single column as output, returning a StructArray is desired in many cases. However, accessing fields of the returned struct results in redundant calls to the UDF.
SELECT
example_struct(c)['a'],
example_struct(c)['b']
FROM (SELECT unnest(range(1,100)) as c)Datafusion produces the following projection step for the query, resulting in calling the UDF with the same column twice.
ProjectionExec: expr=[get_field(example_struct(c@0), a) as example_struct(c)[a], get_field(example_struct(c@0), b) as example_struct(c)[b]]
Note that calling the UDF in a CTE or view does not change the execution plan.
Here is a minimal example https://github.com/liningpan/udf-get-field-optimization.
Describe the solution you'd like
@adriangb mentioned that CSE (Common Sub-expression Elimination) optimizer might be able to handle this.
Describe alternatives you've considered
No response
Additional context
No response
Activity
tohuya6 commentedon Jul 17, 2026
take
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