From d24bae34d731b9f9080b45b99dea9866c8b54333 Mon Sep 17 00:00:00 2001
From: Liang-Chi Hsieh <viirya@gmail.com>
Date: Wed, 13 Apr 2022 17:48:35 -0700
Subject: [PATCH 1/3] Fix incorrect buffers for UnionArray

---
 arrow/src/array/data.rs | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/arrow/src/array/data.rs b/arrow/src/array/data.rs
index 551bf536cb33..043e4af76f88 100644
--- a/arrow/src/array/data.rs
+++ b/arrow/src/array/data.rs
@@ -219,8 +219,14 @@ pub(crate) fn into_buffers(
         DataType::Utf8
         | DataType::Binary
         | DataType::LargeUtf8
-        | DataType::LargeBinary
-        | DataType::Union(_, _) => vec![buffer1.into(), buffer2.into()],
+        | DataType::LargeBinary => vec![buffer1.into(), buffer2.into()],
+        DataType::Union(_, mode) => {
+            match mode {
+                // Based on Union's DataTypeLayout
+                UnionMode::Sparse => vec![buffer1.into()],
+                UnionMode::Dense => vec![buffer1.into(), buffer2.into()],
+            }
+        }
         _ => vec![buffer1.into()],
     }
 }

From ee9ec378649369763bb55715cd8ff2faf595f42e Mon Sep 17 00:00:00 2001
From: Liang-Chi Hsieh <viirya@gmail.com>
Date: Thu, 14 Apr 2022 09:30:41 -0700
Subject: [PATCH 2/3] Add test

---
 arrow/src/array/data.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arrow/src/array/data.rs b/arrow/src/array/data.rs
index 043e4af76f88..fe8020a04a18 100644
--- a/arrow/src/array/data.rs
+++ b/arrow/src/array/data.rs
@@ -2600,4 +2600,21 @@ mod tests {
 
         assert_eq!(&struct_array_slice, &cloned);
     }
+
+    #[test]
+    fn test_into_buffers() {
+        let data_types = vec![
+            DataType::Union(vec![], UnionMode::Dense),
+            DataType::Union(vec![], UnionMode::Sparse),
+        ];
+
+        for data_type in data_types {
+            let buffers = new_buffers(&data_type, 0);
+            let [buffer1, buffer2] = buffers;
+            let buffers = into_buffers(&data_type, buffer1, buffer2);
+
+            let layout = layout(&data_type);
+            assert_eq!(buffers.len(), layout.buffers.len());
+        }
+    }
 }

From 9f78ddffc0555d2685f27f641e116df6425aee61 Mon Sep 17 00:00:00 2001
From: Liang-Chi Hsieh <viirya@gmail.com>
Date: Thu, 14 Apr 2022 10:45:07 -0700
Subject: [PATCH 3/3] Re-enable test_filter_union_array_sparse

---
 arrow/src/compute/kernels/filter.rs | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arrow/src/compute/kernels/filter.rs b/arrow/src/compute/kernels/filter.rs
index 4ab5b180bf5a..df59ba63c79d 100644
--- a/arrow/src/compute/kernels/filter.rs
+++ b/arrow/src/compute/kernels/filter.rs
@@ -1692,9 +1692,6 @@ mod tests {
     }
 
     #[test]
-    // Fails when validation enabled
-    // https://github.com/apache/arrow-rs/issues/1547
-    #[cfg(not(feature = "force_validate"))]
     fn test_filter_union_array_sparse() {
         let mut builder = UnionBuilder::new_sparse(3);
         builder.append::<Int32Type>("A", 1).unwrap();
@@ -1706,9 +1703,6 @@ mod tests {
     }
 
     #[test]
-    // Fails when validation enabled
-    // https://github.com/apache/arrow-rs/issues/1547
-    #[cfg(not(feature = "force_validate"))]
     fn test_filter_union_array_sparse_with_nulls() {
         let mut builder = UnionBuilder::new_sparse(4);
         builder.append::<Int32Type>("A", 1).unwrap();