timsaucer commented on code in PR #15646:
URL: https://github.com/apache/datafusion/pull/15646#discussion_r2053073575
##########
datafusion/core/tests/user_defined/user_defined_scalar_functions.rs:
##########
@@ -1367,3 +1372,342 @@ async fn register_alltypes_parquet(ctx:
&SessionContext) -> Result<()> {
async fn plan_and_collect(ctx: &SessionContext, sql: &str) ->
Result<Vec<RecordBatch>> {
ctx.sql(sql).await?.collect().await
}
+
+#[derive(Debug)]
+struct MetadataBasedUdf {
+ name: String,
+ signature: Signature,
+ metadata: HashMap<String, String>,
+}
+
+impl MetadataBasedUdf {
+ fn new(metadata: HashMap<String, String>) -> Self {
+ // The name we return must be unique. Otherwise we will not call
distinct
+ // instances of this UDF. This is a small hack for the unit tests to
get unique
+ // names, but you could do something more elegant with the metadata.
+ let name = format!("metadata_based_udf_{}", metadata.len());
+ Self {
+ name,
+ signature: Signature::exact(vec![DataType::UInt64],
Volatility::Immutable),
+ metadata,
+ }
+ }
+}
+
+impl ScalarUDFImpl for MetadataBasedUdf {
+ fn as_any(&self) -> &dyn Any {
+ self
+ }
+
+ fn name(&self) -> &str {
+ &self.name
+ }
+
+ fn signature(&self) -> &Signature {
+ &self.signature
+ }
+
+ fn return_type(&self, _args: &[DataType]) -> Result<DataType> {
+ unimplemented!(
+ "this should never be called since return_field_from_args is
implemented"
+ );
+ }
+
+ fn return_field_from_args(&self, _args: ReturnFieldArgs) -> Result<Field> {
+ Ok(Field::new(self.name(), DataType::UInt64, true)
+ .with_metadata(self.metadata.clone()))
+ }
Review Comment:
@paleolimbot I have an end to end example working on my company's code, so
if there are still gaps from what you need please let me know!
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