Use an index lookup for O(1) field index access

apache · Nov 4, 2024 · 6b77dd7 · 6b77dd7
1 parent 45b3697
commit 6b77dd7
Showing 1 changed file with 9 additions and 1 deletion.
diff --git a/csharp/src/Apache.Arrow/Schema.cs b/csharp/src/Apache.Arrow/Schema.cs
@@ -31,6 +31,7 @@ public partial class Schema : IRecordType
         private readonly List<Field> _fieldsList;
 
         public ILookup<string, Field> FieldsLookup { get; }
+        private ILookup<string, int> _fieldsIndexLookup { get; }
 
         public IReadOnlyDictionary<string, string> Metadata { get; }
 
@@ -54,6 +55,10 @@ public Schema(
             _fieldsDictionary = FieldsLookup.ToDictionary(g => g.Key, g => g.First());
 
             Metadata = metadata?.ToDictionary(kv => kv.Key, kv => kv.Value);
+
+            _fieldsIndexLookup = _fieldsList
+                .Select((x, idx) => (Item: x, Index: idx))
+                .ToLookup(x => x.Item.Name, x => x.Index, StringComparer.CurrentCulture);
         }
 
         internal Schema(List<Field> fieldsList, IReadOnlyDictionary<string, string> metadata, bool copyCollections)
@@ -80,7 +85,10 @@ public int GetFieldIndex(string name, StringComparer comparer)
 
         public int GetFieldIndex(string name, IEqualityComparer<string> comparer = default)
         {
-            comparer ??= StringComparer.CurrentCulture;
+            if (comparer == null)
+            {
+                return _fieldsIndexLookup[name].First();
+            }
 
             return _fieldsList.IndexOf(_fieldsList.First(x => comparer.Equals(x.Name, name)));
         }