Fix arrow list type to duckdb logical type conversion (#574)

When registering a scalar function which returns a list value, duckdb
returns an error:

```
thread '<unnamed>' panicked at src/lib.rs:31:10:
Failed to register split_words function: DuckDBFailure(Error { code: Unknown, extended_code: 1 }, None)
```

This PR fixes this issue by replacing
`LogicalTypeId::try_from(..).into()` by `to_duckdb_logical_type`.

Author: mlafeldt

crates/duckdb/src/vscalar/arrow.rs

@@ -6,8 +6,8 @@ use arrow::{
 };
 
 use crate::{
-    core::{DataChunkHandle, LogicalTypeId},
-    vtab::arrow::{data_chunk_to_arrow, write_arrow_array_to_vector, WritableVector},
+    core::DataChunkHandle,
+    vtab::arrow::{data_chunk_to_arrow, to_duckdb_logical_type, write_arrow_array_to_vector, WritableVector},
 };
 
 use super::{ScalarFunctionSignature, ScalarParams, VScalar};
@@ -35,14 +35,12 @@ impl From<ArrowScalarParams> for ScalarParams {
             ArrowScalarParams::Exact(params) => Self::Exact(
                 params
                     .into_iter()
-                    .map(|v| LogicalTypeId::try_from(&v).expect("type should be converted").into())
+                    .map(|v| to_duckdb_logical_type(&v).expect("type should be converted"))
                     .collect(),
             ),
-            ArrowScalarParams::Variadic(param) => Self::Variadic(
-                LogicalTypeId::try_from(&param)
-                    .expect("type should be converted")
-                    .into(),
-            ),
+            ArrowScalarParams::Variadic(param) => {
+                Self::Variadic(to_duckdb_logical_type(&param).expect("type should be converted"))
+            }
         }
     }
 }
@@ -107,9 +105,7 @@ where
             .into_iter()
             .map(|sig| ScalarFunctionSignature {
                 parameters: sig.parameters.map(Into::into),
-                return_type: LogicalTypeId::try_from(&sig.return_type)
-                    .expect("type should be converted")
-                    .into(),
+                return_type: to_duckdb_logical_type(&sig.return_type).expect("type should be converted"),
             })
             .collect()
     }
@@ -333,4 +329,58 @@ mod test {
 
         Ok(())
     }
+
+    #[test]
+    fn test_split_function() -> Result<(), Box<dyn Error>> {
+        struct SplitFunction {}
+
+        impl VArrowScalar for SplitFunction {
+            type State = ();
+
+            fn invoke(_: &Self::State, input: RecordBatch) -> Result<Arc<dyn Array>, Box<dyn std::error::Error>> {
+                let strings = input.column(0).as_any().downcast_ref::<StringArray>().unwrap();
+
+                let mut builder = arrow::array::ListBuilder::new(arrow::array::StringBuilder::with_capacity(
+                    strings.len(),
+                    strings.len() * 10,
+                ));
+
+                for s in strings.iter() {
+                    let s = s.unwrap();
+                    for split_value in s.split(' ').collect::<Vec<_>>() {
+                        builder.values().append_value(split_value);
+                    }
+                    builder.append(true);
+                }
+
+                Ok(Arc::new(builder.finish()))
+            }
+
+            fn signatures() -> Vec<ArrowFunctionSignature> {
+                vec![ArrowFunctionSignature::exact(
+                    vec![DataType::Utf8],
+                    DataType::List(Arc::new(arrow::datatypes::Field::new("item", DataType::Utf8, true))),
+                )]
+            }
+        }
+
+        let conn = Connection::open_in_memory()?;
+        conn.register_scalar_function::<SplitFunction>("split_string")?;
+
+        // Test with single string
+        let batches = conn
+            .prepare("select split_string('hello world') as result")?
+            .query_arrow([])?
+            .collect::<Vec<_>>();
+
+        let array = batches[0].column(0);
+        let list_array = array.as_any().downcast_ref::<arrow::array::ListArray>().unwrap();
+        let values = list_array.value(0);
+        let string_values = values.as_any().downcast_ref::<StringArray>().unwrap();
+
+        assert_eq!(string_values.value(0), "hello");
+        assert_eq!(string_values.value(1), "world");
+
+        Ok(())
+    }
 }