From 5228bb31728eacb790dcbefda07b07a9d2d4b8f7 Mon Sep 17 00:00:00 2001
From: jiangzhx <jiangzhx@gmail.com>
Date: Thu, 8 Jun 2023 12:50:00 +0800
Subject: [PATCH 1/2] Make the struct function return the correct data type.

---
 datafusion/expr/src/function.rs | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/datafusion/expr/src/function.rs b/datafusion/expr/src/function.rs
index ed5df5766720c..bec672ab6f6c3 100644
--- a/datafusion/expr/src/function.rs
+++ b/datafusion/expr/src/function.rs
@@ -352,7 +352,14 @@ pub fn return_type(
             _ => Ok(DataType::Float64),
         },
 
-        BuiltinScalarFunction::Struct => Ok(DataType::Struct(Fields::empty())),
+        BuiltinScalarFunction::Struct => {
+            let return_fields = input_expr_types
+                .iter()
+                .enumerate()
+                .map(|(pos, dt)| Field::new(format!("c{pos}"), dt.clone(), true))
+                .collect::<Vec<Field>>();
+            Ok(DataType::Struct(Fields::from(return_fields)))
+        }
 
         BuiltinScalarFunction::Atan2 => match &input_expr_types[0] {
             DataType::Float32 => Ok(DataType::Float32),

From 12f45b1e3094ba373003f67c1f15a3c83961104f Mon Sep 17 00:00:00 2001
From: jiangzhx <jiangzhx@gmail.com>
Date: Thu, 8 Jun 2023 14:21:18 +0800
Subject: [PATCH 2/2] add testcase

---
 .../sqllogictests/test_files/functions.slt    | 22 +++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/datafusion/core/tests/sqllogictests/test_files/functions.slt b/datafusion/core/tests/sqllogictests/test_files/functions.slt
index 0cb54711cfbd7..b52dca5770679 100644
--- a/datafusion/core/tests/sqllogictests/test_files/functions.slt
+++ b/datafusion/core/tests/sqllogictests/test_files/functions.slt
@@ -458,3 +458,25 @@ SELECT v1, v2, ROWNUMBER() OVER(ORDER BY v1) from test;
 
 statement ok
 drop table test
+
+# Scalar function struct
+statement ok
+create table simple_struct_test (
+    c1 boolean,
+    c2 INT,
+    c3 FLOAT,
+    c4 DOUBLE,
+    a VARCHAR,
+    b TEXT
+) as select *
+from (values
+  (true, 1,3.1,3.14,'str','text')
+);
+
+query ?
+SELECT struct(c1,c2,c3,c4,a,b) from simple_struct_test
+----
+{c0: 1, c1: 1, c2: 3.1, c3: 3.14, c4: str, c5: text}
+
+statement ok
+drop table simple_struct_test
\ No newline at end of file