From f75844246309667158d7df82d4d0666523b8063f Mon Sep 17 00:00:00 2001
From: Matt Butrovich <mbutrovich@gmail.com>
Date: Wed, 13 Nov 2024 14:35:45 -0500
Subject: [PATCH] Selectively generate projection vector.

---
 .../core/src/execution/datafusion/planner.rs  | 28 ++++++++++---------
 1 file changed, 15 insertions(+), 13 deletions(-)

diff --git a/native/core/src/execution/datafusion/planner.rs b/native/core/src/execution/datafusion/planner.rs
index 1268a2ff4..cd79e8e0b 100644
--- a/native/core/src/execution/datafusion/planner.rs
+++ b/native/core/src/execution/datafusion/planner.rs
@@ -968,16 +968,6 @@ impl PhysicalPlanner {
                     )
                     .unwrap(),
                 );
-                assert!(!required_schema_arrow.fields.is_empty());
-
-                let mut projection_vector: Vec<usize> =
-                    Vec::with_capacity(required_schema_arrow.fields.len());
-                // TODO: could be faster with a hashmap rather than iterating over data_schema_arrow with index_of.
-                required_schema_arrow.fields.iter().for_each(|field| {
-                    projection_vector.push(data_schema_arrow.index_of(field.name()).unwrap());
-                });
-
-                assert_eq!(projection_vector.len(), required_schema_arrow.fields.len());
 
                 // Convert the Spark expressions to Physical expressions
                 let data_filters: Result<Vec<Arc<dyn PhysicalExpr>>, ExecutionError> = scan
@@ -1028,10 +1018,22 @@ impl PhysicalPlanner {
                 assert_eq!(file_groups.len(), partition_count);
 
                 let object_store_url = ObjectStoreUrl::local_filesystem();
-                let file_scan_config =
+                let mut file_scan_config =
                     FileScanConfig::new(object_store_url, Arc::clone(&data_schema_arrow))
-                        .with_file_groups(file_groups)
-                        .with_projection(Some(projection_vector));
+                        .with_file_groups(file_groups);
+
+                // Check for projection, if so generate the vector and add to FileScanConfig.
+                if !required_schema_arrow.fields.is_empty() {
+                    let mut projection_vector: Vec<usize> =
+                        Vec::with_capacity(required_schema_arrow.fields.len());
+                    // TODO: could be faster with a hashmap rather than iterating over data_schema_arrow with index_of.
+                    required_schema_arrow.fields.iter().for_each(|field| {
+                        projection_vector.push(data_schema_arrow.index_of(field.name()).unwrap());
+                    });
+
+                    assert_eq!(projection_vector.len(), required_schema_arrow.fields.len());
+                    file_scan_config = file_scan_config.with_projection(Some(projection_vector));
+                }
 
                 let mut table_parquet_options = TableParquetOptions::new();
                 // TODO: Maybe these are configs?