Jefffrey commented on code in PR #19335:
URL: https://github.com/apache/datafusion/pull/19335#discussion_r2621155616
##########
datafusion/functions-aggregate/src/first_last.rs:
##########
@@ -1075,6 +1087,18 @@ impl AggregateUDFImpl for LastValue {
Ok(arg_types[0].clone())
Review Comment:
Ditto
##########
datafusion/sqllogictest/test_files/metadata.slt:
##########
@@ -235,7 +235,56 @@ order by 1 asc nulls last;
3 1
NULL 1
+# Regression test: first_value should preserve metadata
Review Comment:
I noticed for the existing regression tests in this file, they don't
actually check metadata 🤔
https://github.com/apache/datafusion/blob/58377bf2e30315438f6cff047874c3fac770f31e/datafusion/sqllogictest/test_files/metadata.slt#L63-L67
With this new UDF we can look into updating those tests to be more similar
to the ones introduced here
##########
datafusion/sqllogictest/src/test_context.rs:
##########
@@ -398,6 +398,58 @@ pub async fn register_metadata_tables(ctx:
&SessionContext) {
.unwrap();
ctx.register_batch("table_with_metadata", batch).unwrap();
+
+ // Register the get_metadata UDF for testing metadata preservation
+ ctx.register_udf(ScalarUDF::from(GetMetadataUdf::new()));
+}
+
+/// UDF to extract metadata from a field for testing purposes
+/// Usage: get_metadata(expr, 'key') -> returns the metadata value or NULL
+#[derive(Debug, PartialEq, Eq, Hash)]
+struct GetMetadataUdf {
Review Comment:
I wonder if this is useful enough to introduce as a function to datafusion
itself, instead of being only in SLT? 🤔
##########
datafusion/functions-aggregate/src/first_last.rs:
##########
@@ -137,6 +137,18 @@ impl AggregateUDFImpl for FirstValue {
Ok(arg_types[0].clone())
Review Comment:
Ideally we should have `return_type` return an internal error instead of
leaving it implemented if we use `return_field` now
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