From be56f11ff34ecaed8894e7393a19e85fd584d65d Mon Sep 17 00:00:00 2001
From: Kevin Lim <kszlim@gmail.com>
Date: Sun, 20 Oct 2024 03:08:24 -0700
Subject: [PATCH 1/3] Add support for building FixedSizeListBuilder in
 struct_builder's make_builders

---
 arrow-array/src/builder/struct_builder.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/arrow-array/src/builder/struct_builder.rs b/arrow-array/src/builder/struct_builder.rs
index c0e49b939f2c..06457fd30cbe 100644
--- a/arrow-array/src/builder/struct_builder.rs
+++ b/arrow-array/src/builder/struct_builder.rs
@@ -252,7 +252,11 @@ pub fn make_builder(datatype: &DataType, capacity: usize) -> Box<dyn ArrayBuilde
         DataType::LargeList(field) => {
             let builder = make_builder(field.data_type(), capacity);
             Box::new(LargeListBuilder::with_capacity(builder, capacity).with_field(field.clone()))
-        }
+        },
+        DataType::FixedSizeList(field, size) => {
+            let builder = make_builder(field.data_type(), capacity);
+            Box::new(FixedSizeListBuilder::with_capacity(builder, *size, capacity).with_field(field.clone()))
+        },
         DataType::Map(field, _) => match field.data_type() {
             DataType::Struct(fields) => {
                 let map_field_names = MapFieldNames {

From b9539e2ddad23f60352de64dac92be7fe9a9e0ee Mon Sep 17 00:00:00 2001
From: Kevin Lim <kszlim@gmail.com>
Date: Sun, 20 Oct 2024 03:26:23 -0700
Subject: [PATCH 2/3] Fix formatting

---
 arrow-array/src/builder/struct_builder.rs | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arrow-array/src/builder/struct_builder.rs b/arrow-array/src/builder/struct_builder.rs
index 06457fd30cbe..595d51f23151 100644
--- a/arrow-array/src/builder/struct_builder.rs
+++ b/arrow-array/src/builder/struct_builder.rs
@@ -252,11 +252,14 @@ pub fn make_builder(datatype: &DataType, capacity: usize) -> Box<dyn ArrayBuilde
         DataType::LargeList(field) => {
             let builder = make_builder(field.data_type(), capacity);
             Box::new(LargeListBuilder::with_capacity(builder, capacity).with_field(field.clone()))
-        },
+        }
         DataType::FixedSizeList(field, size) => {
             let builder = make_builder(field.data_type(), capacity);
-            Box::new(FixedSizeListBuilder::with_capacity(builder, *size, capacity).with_field(field.clone()))
-        },
+            Box::new(
+                FixedSizeListBuilder::with_capacity(builder, *size, capacity)
+                    .with_field(field.clone()),
+            )
+        }
         DataType::Map(field, _) => match field.data_type() {
             DataType::Struct(fields) => {
                 let map_field_names = MapFieldNames {

From b03161ada4522789c46effb6d4d380dac2838f0e Mon Sep 17 00:00:00 2001
From: Kevin Lim <kszlim@gmail.com>
Date: Mon, 21 Oct 2024 10:28:26 -0700
Subject: [PATCH 3/3] Make suggested fixes + add test

---
 arrow-array/src/builder/struct_builder.rs | 31 +++++++++++++++++++++--
 1 file changed, 29 insertions(+), 2 deletions(-)

diff --git a/arrow-array/src/builder/struct_builder.rs b/arrow-array/src/builder/struct_builder.rs
index 595d51f23151..4561e052581c 100644
--- a/arrow-array/src/builder/struct_builder.rs
+++ b/arrow-array/src/builder/struct_builder.rs
@@ -254,9 +254,14 @@ pub fn make_builder(datatype: &DataType, capacity: usize) -> Box<dyn ArrayBuilde
             Box::new(LargeListBuilder::with_capacity(builder, capacity).with_field(field.clone()))
         }
         DataType::FixedSizeList(field, size) => {
-            let builder = make_builder(field.data_type(), capacity);
+            let size = *size;
+            let values_builder_capacity = {
+                let size: usize = size.try_into().unwrap();
+                capacity * size
+            };
+            let builder = make_builder(field.data_type(), values_builder_capacity);
             Box::new(
-                FixedSizeListBuilder::with_capacity(builder, *size, capacity)
+                FixedSizeListBuilder::with_capacity(builder, size, capacity)
                     .with_field(field.clone()),
             )
         }
@@ -527,6 +532,28 @@ mod tests {
         assert_eq!(0, builder.len());
     }
 
+    #[test]
+    fn test_build_fixed_size_list() {
+        const LIST_LENGTH: i32 = 4;
+        let fixed_size_list_dtype =
+            DataType::new_fixed_size_list(DataType::Int32, LIST_LENGTH, false);
+        let mut builder = make_builder(&fixed_size_list_dtype, 10);
+        let builder = builder
+            .as_any_mut()
+            .downcast_mut::<FixedSizeListBuilder<Box<dyn ArrayBuilder>>>();
+        match builder {
+            Some(builder) => {
+                assert_eq!(builder.value_length(), LIST_LENGTH);
+                assert!(builder
+                    .values()
+                    .as_any_mut()
+                    .downcast_mut::<Int32Builder>()
+                    .is_some());
+            }
+            None => panic!("expected FixedSizeListBuilder, got a different builder type"),
+        }
+    }
+
     #[test]
     fn test_struct_array_builder_finish_cloned() {
         let int_builder = Int32Builder::new();