From 6c418ea3f0cee7544094a28ee4a4f43efcb760ce Mon Sep 17 00:00:00 2001
From: Nikita Kazmin <vonzshik@gmail.com>
Date: Mon, 24 Mar 2025 14:07:41 +0300
Subject: [PATCH] Fix adding to hash lookup while renaming an unnamed parameter

---
 src/Npgsql/NpgsqlParameterCollection.cs       |  2 +-
 .../NpgsqlParameterCollectionTests.cs         | 28 +++++++++++++++++++
 2 files changed, 29 insertions(+), 1 deletion(-)

diff --git a/src/Npgsql/NpgsqlParameterCollection.cs b/src/Npgsql/NpgsqlParameterCollection.cs
index 2e6b0f5012..106f681f0b 100644
--- a/src/Npgsql/NpgsqlParameterCollection.cs
+++ b/src/Npgsql/NpgsqlParameterCollection.cs
@@ -143,7 +143,7 @@ internal void ChangeParameterName(NpgsqlParameter parameter, string? value)
         var oldTrimmedName = parameter.TrimmedName;
         parameter.ChangeParameterName(value);
 
-        if (_caseInsensitiveLookup is null || _caseInsensitiveLookup.Count == 0)
+        if (_caseInsensitiveLookup is null)
             return;
 
         var index = IndexOf(parameter);
diff --git a/test/Npgsql.Tests/NpgsqlParameterCollectionTests.cs b/test/Npgsql.Tests/NpgsqlParameterCollectionTests.cs
index e2c7ba364c..f6a188817b 100644
--- a/test/Npgsql.Tests/NpgsqlParameterCollectionTests.cs
+++ b/test/Npgsql.Tests/NpgsqlParameterCollectionTests.cs
@@ -71,6 +71,34 @@ public void Hash_lookup_parameter_rename_bug()
         Assert.That(command.Parameters.IndexOf("a_new_name"), Is.GreaterThanOrEqualTo(0));
     }
 
+    [Test]
+    [IssueLink("https://github.com/npgsql/npgsql/issues/6067")]
+    public void Hash_lookup_unnamed_parameter_rename_bug()
+    {
+        if (_compatMode == CompatMode.TwoPass)
+            return;
+
+        using var command = new NpgsqlCommand();
+
+        for (var i = 0; i < 3; i++)
+        {
+            // Put plenty of parameters in the collection to turn on hash lookup functionality.
+            for (var j = 0; j < LookupThreshold; j++)
+            {
+                // Create and add an unnamed parameter before renaming it
+                var parameter = command.CreateParameter();
+                command.Parameters.Add(parameter);
+                parameter.ParameterName = $"{j}";
+            }
+
+            // Make sure hash lookup is generated.
+            Assert.AreEqual(command.Parameters["3"].ParameterName, "3");
+
+            // Remove all parameters to clear hash lookup
+            command.Parameters.Clear();
+        }
+    }
+
     [Test]
     public void Remove_duplicate_parameter([Values(LookupThreshold, LookupThreshold - 2)] int count)
     {