From c2c87c5c618743f6ff4a7a965e3ac88b58df43cc Mon Sep 17 00:00:00 2001
From: Marius Thesing <marius.thesing@gmail.com>
Date: Sat, 8 Aug 2026 11:46:33 +0200
Subject: [PATCH] reduce allocations in NpgsqlParameterCollection.AddRange

---
 src/Npgsql/NpgsqlParameterCollection.cs       |  1 +
 test/Npgsql.Benchmarks/ParameterCollection.cs | 30 +++++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 test/Npgsql.Benchmarks/ParameterCollection.cs

diff --git a/src/Npgsql/NpgsqlParameterCollection.cs b/src/Npgsql/NpgsqlParameterCollection.cs
index 917eb9311b..d5fff69c6d 100644
--- a/src/Npgsql/NpgsqlParameterCollection.cs
+++ b/src/Npgsql/NpgsqlParameterCollection.cs
@@ -589,6 +589,7 @@ IEnumerator<NpgsqlParameter> IEnumerable<NpgsqlParameter>.GetEnumerator()
     public override void AddRange(Array values)
     {
         ArgumentNullException.ThrowIfNull(values);
+        InternalList.EnsureCapacity(InternalList.Count + values.Length);
 
         foreach (var parameter in values)
             Add(Cast(parameter));
diff --git a/test/Npgsql.Benchmarks/ParameterCollection.cs b/test/Npgsql.Benchmarks/ParameterCollection.cs
new file mode 100644
index 0000000000..0e09fb458b
--- /dev/null
+++ b/test/Npgsql.Benchmarks/ParameterCollection.cs
@@ -0,0 +1,30 @@
+using System.Collections.Generic;
+using BenchmarkDotNet.Attributes;
+
+namespace Npgsql.Benchmarks;
+
+[MemoryDiagnoser]
+public class ParameterCollection
+{
+    private NpgsqlParameter[] manyParameters = [];
+
+    [IterationSetup]
+    public void IterationSetup()
+    {
+        List<NpgsqlParameter> parameters = [];
+
+        for (var i = 0; i < 2000; i++)
+        {
+            parameters.Add(new NpgsqlParameter());
+        }
+
+        manyParameters = parameters.ToArray();
+    }
+
+    [Benchmark]
+    public void AddRange()
+    {
+        NpgsqlParameterCollection parameterCollection = [];
+        parameterCollection.AddRange(manyParameters);
+    }
+}