fix: #10020 make concat function support array concatenation

datafusion/functions/src/string/concat.rs

@@ -15,8 +15,9 @@
 // specific language governing permissions and limitations
 // under the License.
 
-use arrow::array::{Array, as_largestring_array};
-use arrow::datatypes::DataType;
+use arrow::array::{Array, as_largestring_array, ArrayRef};
+use arrow::datatypes::{DataType, Field, TimeUnit};
+use arrow_array::types::*;
 use datafusion_expr::sort_properties::ExprProperties;
 use std::any::Any;
 use std::sync::Arc;
@@ -26,10 +27,10 @@ use crate::strings::{
     ColumnarValueRef, LargeStringArrayBuilder, StringArrayBuilder, StringViewArrayBuilder,
 };
 use datafusion_common::cast::{as_string_array, as_string_view_array};
-use datafusion_common::{Result, ScalarValue, internal_err, plan_err};
-use datafusion_expr::expr::ScalarFunction;
+use datafusion_common::{Result, ScalarValue, internal_err, plan_err, exec_err};
+use datafusion_expr::expr::{ScalarFunction, ScalarFunctionExpr};
 use datafusion_expr::simplify::{ExprSimplifyResult, SimplifyInfo};
-use datafusion_expr::{ColumnarValue, Documentation, Expr, Volatility, lit};
+use datafusion_expr::{ColumnarValue, Documentation, Expr, Volatility, lit, BuiltinScalarFunction};
 use datafusion_expr::{ScalarFunctionArgs, ScalarUDFImpl, Signature};
 use datafusion_macros::user_doc;
 
@@ -67,13 +68,42 @@ impl ConcatFunc {
     pub fn new() -> Self {
         use DataType::*;
         Self {
-            signature: Signature::variadic(
-                vec![Utf8View, Utf8, LargeUtf8],
-                Volatility::Immutable,
+            signature: Signature::variadic_any(Volatility::Immutable)
             ),
         }
     }
-}
+
+    // Check if any argument is an array type
+    fn has_array_args(args: &[ColumnarValue]) -> bool {
+        use arrow::datatypes::DataType::*;
+        args.iter().any(|arg| match arg {
+            ColumnarValue::Array(arr) => matches!(arr.data_type(), List(_)),
+            ColumnarValue::Scalar(scalar) => matches!(scalar, ScalarValue::List(_, _)),
+        })
+    }
+
+    // Convert arguments to array_concat function
+    fn to_array_concat(args: Vec<Expr>) -> Result<Expr> {
+        let array_concat = BuiltinScalarFunction::ArrayConcat;
+        let args = args.into_iter()
+            .map(|arg| {
+                // If the argument is not already an array, wrap it in an array
+                if !matches!(arg.get_type(&DataType::Null).unwrap_or_default(), DataType::List(_)) {
+                    Ok(Expr::ScalarFunction(ScalarFunction::new(
+                        BuiltinScalarFunction::MakeArray,
+                        vec![arg],
+                    )))
+                } else {
+                    Ok(arg)
+                }
+            })
+            .collect::<Result<Vec<_>>>()?;
+
+        Ok(Expr::ScalarFunction(ScalarFunction::new(
+            array_concat,
+            args,
+        )))
+    }
 
 impl ScalarUDFImpl for ConcatFunc {
     fn as_any(&self) -> &dyn Any {
@@ -90,22 +120,40 @@ impl ScalarUDFImpl for ConcatFunc {
 
     fn return_type(&self, arg_types: &[DataType]) -> Result<DataType> {
         use DataType::*;
+
+        // If any argument is an array, return the array type
+        if arg_types.iter().any(|t| matches!(t, List(_))) {
+            // Find the first array type to use as the base
+            if let Some(DataType::List(field)) = arg_types.iter().find(|t| matches!(t, List(_))) {
+                return Ok(DataType::List(field.clone()));
+            }
+        }
+
+        // Otherwise, use the existing string type logic
         let mut dt = &Utf8;
-        arg_types.iter().for_each(|data_type| {
+        for data_type in arg_types {
             if data_type == &Utf8View {
                 dt = data_type;
             }
             if data_type == &LargeUtf8 && dt != &Utf8View {
                 dt = data_type;
             }
-        });
-
-        Ok(dt.to_owned())
+        }
+        Ok(dt.clone())
     }
 
     /// Concatenates the text representations of all the arguments. NULL arguments are ignored.
     /// concat('abcde', 2, NULL, 22) = 'abcde222'
     fn invoke_with_args(&self, args: ScalarFunctionArgs) -> Result<ColumnarValue> {
+        // Check if any argument is an array
+        if Self::has_array_args(&args.args) {
+            // Convert to array_concat expression and evaluate it
+            let exprs: Vec<Expr> = args.args.into_iter().map(|a| a.into_expr()).collect();
+            let expr = Self::to_array_concat(exprs)?;
+            return expr.eval(args.context);
+        }
+
+        // Original string concatenation logic
         let ScalarFunctionArgs { args, .. } = args;
 
         let mut return_datatype = DataType::Utf8;