fix: preserve argument types in max_by/min_by with dictionary inputs

src/max_min_by.rs

@@ -45,7 +45,9 @@ fn get_min_max_by_result_type(
     match &input_types[0] {
         arrow::datatypes::DataType::Dictionary(_, dict_value_type) => {
             // x add checker, if the value type is complex data type
-            Ok(vec![dict_value_type.deref().clone()])
+            let mut result = vec![dict_value_type.deref().clone()];
+            result.extend_from_slice(&input_types[1..]); // Preserve all other argument types
+            Ok(result)
         }
         _ => Ok(input_types.to_vec()),
     }
@@ -207,3 +209,212 @@ impl logical_expr::AggregateUDFImpl for MinByFunction {
         Some(Box::new(simplify))
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use datafusion::arrow::array::{
+        ArrayRef, Float64Array, Int64Array, RecordBatch, StringArray, UInt64Array,
+    };
+    use datafusion::arrow::datatypes::{DataType, Field, Schema};
+    use datafusion::datasource::MemTable;
+    use datafusion::prelude::SessionContext;
+    use std::any::Any;
+    use std::sync::Arc;
+
+    #[cfg(test)]
+    mod tests_max_by {
+        use crate::max_min_by::max_by_udaf;
+        use crate::max_min_by::tests::{
+            extract_single_float64, extract_single_int64, extract_single_string, test_ctx,
+        };
+        use datafusion::error::Result;
+        use datafusion::prelude::SessionContext;
+
+        #[tokio::test]
+        async fn test_max_by_string_int() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT max_by(string, int64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "h");
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_string_float() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT max_by(string, float64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "h");
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_float_string() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT max_by(float64, string) FROM types")
+                .await?;
+            assert_eq!(extract_single_float64(df.collect().await?), 8.0);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_int_string() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT max_by(int64, string) FROM types")
+                .await?;
+            assert_eq!(extract_single_int64(df.collect().await?), 8);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_max_by_dictionary_int() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT max_by(dict_string, int64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "h");
+            Ok(())
+        }
+
+        fn ctx() -> Result<SessionContext> {
+            let ctx = test_ctx()?;
+            ctx.register_udaf(max_by_udaf().as_ref().clone());
+            Ok(ctx)
+        }
+    }
+
+    #[cfg(test)]
+    mod test_min_by {
+        use crate::max_min_by::min_by_udaf;
+        use crate::max_min_by::tests::{
+            extract_single_float64, extract_single_int64, extract_single_string, test_ctx,
+        };
+        use datafusion::error::Result;
+        use datafusion::prelude::SessionContext;
+
+        #[tokio::test]
+        async fn test_min_by_string_int() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT min_by(string, int64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "a");
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_string_float() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT min_by(string, float64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "a");
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_float_string() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT min_by(float64, string) FROM types")
+                .await?;
+            assert_eq!(extract_single_float64(df.collect().await?), 0.5);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_int_string() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT min_by(int64, string) FROM types")
+                .await?;
+            assert_eq!(extract_single_int64(df.collect().await?), 1);
+            Ok(())
+        }
+
+        #[tokio::test]
+        async fn test_min_by_dictionary_int() -> Result<()> {
+            let df = ctx()?
+                .sql("SELECT min_by(dict_string, int64) FROM types")
+                .await?;
+            assert_eq!(extract_single_string(df.collect().await?), "a");
+            Ok(())
+        }
+
+        fn ctx() -> Result<SessionContext> {
+            let ctx = test_ctx()?;
+            ctx.register_udaf(min_by_udaf().as_ref().clone());
+            Ok(ctx)
+        }
+    }
+
+    pub(super) fn test_schema() -> Arc<Schema> {
+        Arc::new(Schema::new(vec![
+            Field::new("string", DataType::Utf8, false),
+            Field::new_dictionary("dict_string", DataType::Int32, DataType::Utf8, false),
+            Field::new("int64", DataType::Int64, false),
+            Field::new("uint64", DataType::UInt64, false),
+            Field::new("float64", DataType::Float64, false),
+        ]))
+    }
+
+    pub(super) fn test_data(schema: Arc<Schema>) -> Vec<RecordBatch> {
+        use datafusion::arrow::array::DictionaryArray;
+        use datafusion::arrow::datatypes::Int32Type;
+
+        vec![
+            RecordBatch::try_new(
+                schema.clone(),
+                vec![
+                    Arc::new(StringArray::from(vec!["a", "b", "c", "d"])),
+                    Arc::new(
+                        vec![Some("a"), Some("b"), Some("c"), Some("d")]
+                            .into_iter()
+                            .collect::<DictionaryArray<Int32Type>>(),
+                    ),
+                    Arc::new(Int64Array::from(vec![1, 2, 3, 4])),
+                    Arc::new(UInt64Array::from(vec![1, 2, 3, 4])),
+                    Arc::new(Float64Array::from(vec![0.5, 2.0, 3.0, 4.0])),
+                ],
+            )
+            .unwrap(),
+            RecordBatch::try_new(
+                schema.clone(),
+                vec![
+                    Arc::new(StringArray::from(vec!["e", "f", "g", "h"])),
+                    Arc::new(
+                        vec![Some("e"), Some("f"), Some("g"), Some("h")]
+                            .into_iter()
+                            .collect::<DictionaryArray<Int32Type>>(),
+                    ),
+                    Arc::new(Int64Array::from(vec![5, 6, 7, 8])),
+                    Arc::new(UInt64Array::from(vec![5, 6, 7, 8])),
+                    Arc::new(Float64Array::from(vec![5.0, 6.0, 7.0, 8.0])),
+                ],
+            )
+            .unwrap(),
+        ]
+    }
+
+    pub(crate) fn test_ctx() -> datafusion::common::Result<SessionContext> {
+        let schema = test_schema();
+        let table = MemTable::try_new(schema.clone(), vec![test_data(schema)])?;
+        let ctx = SessionContext::new();
+        ctx.register_table("types", Arc::new(table))?;
+        Ok(ctx)
+    }
+
+    fn downcast<T: Any>(col: &ArrayRef) -> &T {
+        col.as_any().downcast_ref::<T>().unwrap()
+    }
+
+    pub(crate) fn extract_single_string(results: Vec<RecordBatch>) -> String {
+        let v1 = downcast::<StringArray>(results[0].column(0));
+        v1.value(0).to_string()
+    }
+
+    pub(crate) fn extract_single_int64(results: Vec<RecordBatch>) -> i64 {
+        let v1 = downcast::<Int64Array>(results[0].column(0));
+        v1.value(0)
+    }
+
+    pub(crate) fn extract_single_float64(results: Vec<RecordBatch>) -> f64 {
+        let v1 = downcast::<Float64Array>(results[0].column(0));
+        v1.value(0)
+    }
+}