From b8ca86a8e36ad34e58e1151b9c1cc1d1d094b1d2 Mon Sep 17 00:00:00 2001
From: Liang-Chi Hsieh <viirya@gmail.com>
Date: Fri, 15 Dec 2023 09:48:34 -0800
Subject: [PATCH] Support MapBuilder in make_builder (#5210)

---
 arrow-array/src/builder/map_builder.rs    | 45 ++++++++++++++++++++++-
 arrow-array/src/builder/struct_builder.rs | 34 ++++++++++++-----
 2 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/arrow-array/src/builder/map_builder.rs b/arrow-array/src/builder/map_builder.rs
index 3a5244ed81a0..5785bb5fafb5 100644
--- a/arrow-array/src/builder/map_builder.rs
+++ b/arrow-array/src/builder/map_builder.rs
@@ -234,7 +234,8 @@ impl<K: ArrayBuilder, V: ArrayBuilder> ArrayBuilder for MapBuilder<K, V> {
 
 #[cfg(test)]
 mod tests {
-    use crate::builder::{Int32Builder, StringBuilder};
+    use crate::builder::{make_builder, Int32Builder, StringBuilder};
+    use crate::{Int32Array, StringArray};
 
     use super::*;
 
@@ -248,4 +249,46 @@ mod tests {
 
         builder.finish();
     }
+
+    #[test]
+    fn test_boxed_map_builder() {
+        let keys_builder = make_builder(&DataType::Utf8, 5);
+        let values_builder = make_builder(&DataType::Int32, 5);
+
+        let mut builder = MapBuilder::new(None, keys_builder, values_builder);
+        builder
+            .keys()
+            .as_any_mut()
+            .downcast_mut::<StringBuilder>()
+            .expect("should be an StringBuilder")
+            .append_value("1");
+        builder
+            .values()
+            .as_any_mut()
+            .downcast_mut::<Int32Builder>()
+            .expect("should be an Int32Builder")
+            .append_value(42);
+        builder.append(true).unwrap();
+
+        let map_array = builder.finish();
+
+        assert_eq!(
+            map_array
+                .keys()
+                .as_any()
+                .downcast_ref::<StringArray>()
+                .expect("should be an StringArray")
+                .value(0),
+            "1"
+        );
+        assert_eq!(
+            map_array
+                .values()
+                .as_any()
+                .downcast_ref::<Int32Array>()
+                .expect("should be an Int32Array")
+                .value(0),
+            42
+        );
+    }
 }
diff --git a/arrow-array/src/builder/struct_builder.rs b/arrow-array/src/builder/struct_builder.rs
index 960949a2f09f..196ae8092b85 100644
--- a/arrow-array/src/builder/struct_builder.rs
+++ b/arrow-array/src/builder/struct_builder.rs
@@ -177,6 +177,24 @@ pub fn make_builder(datatype: &DataType, capacity: usize) -> Box<dyn ArrayBuilde
             let builder = make_builder(field.data_type(), capacity);
             Box::new(LargeListBuilder::with_capacity(builder, capacity))
         }
+        DataType::Map(field, _) => match field.data_type() {
+            DataType::Struct(fields) => {
+                let map_field_names = MapFieldNames {
+                    key: fields[0].name().clone(),
+                    value: fields[1].name().clone(),
+                    entry: field.name().clone(),
+                };
+                let key_builder = make_builder(fields[0].data_type(), capacity);
+                let value_builder = make_builder(fields[1].data_type(), capacity);
+                Box::new(MapBuilder::with_capacity(
+                    Some(map_field_names),
+                    key_builder,
+                    value_builder,
+                    capacity,
+                ))
+            }
+            t => panic!("The field of Map data type {t:?} should has a child Struct field"),
+        },
         DataType::Struct(fields) => Box::new(StructBuilder::from_fields(fields.clone(), capacity)),
         t => panic!("Data type {t:?} is not currently supported"),
     }
@@ -514,19 +532,15 @@ mod tests {
     }
 
     #[test]
-    #[should_panic(
-        expected = "Data type Map(Field { name: \"entries\", data_type: Struct([Field { name: \"keys\", data_type: Int32, nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {} }, Field { name: \"values\", data_type: UInt32, nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {} }]), nullable: false, dict_id: 0, dict_is_ordered: false, metadata: {} }, false) is not currently supported"
-    )]
+    #[should_panic(expected = "Data type Dictionary(Int32, Utf8) is not currently supported")]
     fn test_struct_array_builder_from_schema_unsupported_type() {
-        let keys = Arc::new(Field::new("keys", DataType::Int32, false));
-        let values = Arc::new(Field::new("values", DataType::UInt32, false));
-        let struct_type = DataType::Struct(Fields::from(vec![keys, values]));
-        let map_data_type =
-            DataType::Map(Arc::new(Field::new("entries", struct_type, false)), false);
-
         let fields = vec![
             Field::new("f1", DataType::Int16, false),
-            Field::new("f2", map_data_type, false),
+            Field::new(
+                "f2",
+                DataType::Dictionary(Box::new(DataType::Int32), Box::new(DataType::Utf8)),
+                false,
+            ),
         ];
 
         let _ = StructBuilder::from_fields(fields, 5);