From 97e0c6052630421043840fa11eec33bd4bbc61ff Mon Sep 17 00:00:00 2001
From: framlog <framlog@gmail.com>
Date: Tue, 28 Mar 2023 17:41:45 +0800
Subject: [PATCH] Fix reading ipc files with unordered projections

---
 arrow-ipc/src/reader.rs | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/arrow-ipc/src/reader.rs b/arrow-ipc/src/reader.rs
index bb367f9447d5..bd7e33185a40 100644
--- a/arrow-ipc/src/reader.rs
+++ b/arrow-ipc/src/reader.rs
@@ -650,15 +650,15 @@ pub fn read_record_batch(
     // keep track of buffer and node index, the functions that create arrays mutate these
     let mut buffer_index = 0;
     let mut node_index = 0;
-    let mut arrays = vec![];
 
     let options = RecordBatchOptions::new().with_row_count(Some(batch.length() as usize));
 
     if let Some(projection) = projection {
+        let mut arrays = vec![];
         // project fields
         for (idx, field) in schema.fields().iter().enumerate() {
             // Create array for projected field
-            if projection.contains(&idx) {
+            if let Some(proj_idx) = projection.iter().position(|p| p == &idx) {
                 let triple = create_array(
                     field_nodes,
                     field,
@@ -672,7 +672,7 @@ pub fn read_record_batch(
                 )?;
                 node_index = triple.1;
                 buffer_index = triple.2;
-                arrays.push(triple.0);
+                arrays.push((proj_idx, triple.0));
             } else {
                 // Skip field.
                 // This must be called to advance `node_index` and `buffer_index`.
@@ -681,13 +681,14 @@ pub fn read_record_batch(
                 buffer_index = tuple.1;
             }
         }
-
+        arrays.sort_by_key(|t| t.0);
         RecordBatch::try_new_with_options(
             Arc::new(schema.project(projection)?),
-            arrays,
+            arrays.into_iter().map(|t| t.1).collect(),
             &options,
         )
     } else {
+        let mut arrays = vec![];
         // keep track of index as lists require more than one node
         for field in schema.fields() {
             let triple = create_array(
@@ -1423,6 +1424,17 @@ mod tests {
             // check the projected column equals the expected column
             assert_eq!(projected_column.as_ref(), expected_column.as_ref());
         }
+
+        {
+            // read record batch with reversed projection
+            let reader = FileReader::try_new(
+                std::io::Cursor::new(buf.clone()),
+                Some(vec![3, 2, 1]),
+            );
+            let read_batch = reader.unwrap().next().unwrap().unwrap();
+            let expected_batch = batch.project(&[3, 2, 1]).unwrap();
+            assert_eq!(read_batch, expected_batch);
+        }
     }
 
     #[test]