From f824d7aa0256769ffed91d8ff505230f1960e341 Mon Sep 17 00:00:00 2001
From: "R. Tyler Croy" <rtyler@brokenco.de>
Date: Fri, 20 Sep 2024 12:43:22 +0000
Subject: [PATCH] fix: adopt the right array item name which changed in kernel
 0.3.1

see delta-incubator/delta-kernel-rs#301
---
 crates/core/src/writer/stats.rs | 20 ++++++++++++--------
 1 file changed, 12 insertions(+), 8 deletions(-)

diff --git a/crates/core/src/writer/stats.rs b/crates/core/src/writer/stats.rs
index eee28b8be8..7bc37e7db6 100644
--- a/crates/core/src/writer/stats.rs
+++ b/crates/core/src/writer/stats.rs
@@ -474,6 +474,10 @@ impl AddAssign for AggregatedStats {
 /// the list and items fields from the path, but also need to handle the
 /// peculiar case where the user named the list field "list" or "item".
 ///
+/// NOTE: As of delta_kernel 0.3.1 the name switched from `item` to `element` to line up with the
+/// parquet spec, see
+/// [here](https://github.com/apache/parquet-format/blob/master/LogicalTypes.md#lists)
+///
 /// For example:
 ///
 /// * ["some_nested_list", "list", "item", "list", "item"] -> "some_nested_list"
@@ -495,9 +499,9 @@ fn get_list_field_name(column_descr: &Arc<ColumnDescriptor>) -> Option<String> {
     while let Some(part) = column_path_parts.pop() {
         match (part.as_str(), lists_seen, items_seen) {
             ("list", seen, _) if seen == max_rep_levels => return Some("list".to_string()),
-            ("item", _, seen) if seen == max_rep_levels => return Some("item".to_string()),
+            ("element", _, seen) if seen == max_rep_levels => return Some("element".to_string()),
             ("list", _, _) => lists_seen += 1,
-            ("item", _, _) => items_seen += 1,
+            ("element", _, _) => items_seen += 1,
             (other, _, _) => return Some(other.to_string()),
         }
     }
@@ -789,9 +793,9 @@ mod tests {
         let mut null_count_keys = vec!["some_list", "some_nested_list"];
         null_count_keys.extend_from_slice(min_max_keys.as_slice());
 
-        assert_eq!(min_max_keys.len(), stats.min_values.len());
-        assert_eq!(min_max_keys.len(), stats.max_values.len());
-        assert_eq!(null_count_keys.len(), stats.null_count.len());
+        assert_eq!(min_max_keys.len(), stats.min_values.len(), "min values don't match");
+        assert_eq!(min_max_keys.len(), stats.max_values.len(), "max values don't match");
+        assert_eq!(null_count_keys.len(), stats.null_count.len(), "null counts don't match");
 
         // assert on min values
         for (k, v) in stats.min_values.iter() {
@@ -820,7 +824,7 @@ mod tests {
                 ("uuid", ColumnValueStat::Value(v)) => {
                     assert_eq!("176c770d-92af-4a21-bf76-5d8c5261d659", v.as_str().unwrap())
                 }
-                _ => panic!("Key should not be present"),
+                k => panic!("Key {k:?} should not be present in min_values"),
             }
         }
 
@@ -851,7 +855,7 @@ mod tests {
                 ("uuid", ColumnValueStat::Value(v)) => {
                     assert_eq!("a98bea04-d119-4f21-8edc-eb218b5849af", v.as_str().unwrap())
                 }
-                _ => panic!("Key should not be present"),
+                k => panic!("Key {k:?} should not be present in max_values"),
             }
         }
 
@@ -878,7 +882,7 @@ mod tests {
                 ("some_nested_list", ColumnCountStat::Value(v)) => assert_eq!(100, *v),
                 ("date", ColumnCountStat::Value(v)) => assert_eq!(0, *v),
                 ("uuid", ColumnCountStat::Value(v)) => assert_eq!(0, *v),
-                _ => panic!("Key should not be present"),
+                k => panic!("Key {k:?} should not be present in null_count"),
             }
         }
     }