From fa8fc728a96e53a04b88a07e8421ed49e4c5f226 Mon Sep 17 00:00:00 2001
From: Aleksander Krzeszowski <akpl@users.noreply.github.com>
Date: Tue, 27 Aug 2024 19:03:29 +0200
Subject: [PATCH] Fix co-variant array conversion breaking shared ArrayPool
 (#519)

---
 ClickHouse.Client.Tests/BulkCopyTests.cs     | 24 ++++++++++++++++++++
 ClickHouse.Client/Copy/ClickHouseBulkCopy.cs |  4 ++--
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/ClickHouse.Client.Tests/BulkCopyTests.cs b/ClickHouse.Client.Tests/BulkCopyTests.cs
index 50451f2d..3cb47bbe 100644
--- a/ClickHouse.Client.Tests/BulkCopyTests.cs
+++ b/ClickHouse.Client.Tests/BulkCopyTests.cs
@@ -1,4 +1,5 @@
 using System;
+using System.Buffers;
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
@@ -430,6 +431,29 @@ public async Task ShouldThrowExceptionOnInnerException(double fraction)
         Assert.ThrowsAsync<ClickHouseBulkCopySerializationException>(async () => await bulkCopy.WriteToServerAsync(data, CancellationToken.None));
     }
 
+    [Test]
+    public async Task ShouldNotAffectSharedArrayPool()
+    {
+        var targetTable = "test." + SanitizeTableName($"array_pool");
+
+        await connection.ExecuteStatementAsync($"DROP TABLE IF EXISTS {targetTable}");
+        await connection.ExecuteStatementAsync($"CREATE TABLE IF NOT EXISTS {targetTable} (int Int32, str String, dt DateTime) ENGINE Null");
+
+        const int poolSize = 8;
+        using var bulkCopy = new ClickHouseBulkCopy(connection)
+        {
+            DestinationTableName = targetTable,
+            BatchSize = poolSize
+        };
+
+        await bulkCopy.InitAsync();
+        await bulkCopy.WriteToServerAsync(Enumerable.Repeat(new object[] { 0, "a", DateTime.Now }, 100));
+
+        var rentedArray = ArrayPool<object>.Shared.Rent(poolSize);
+        Assert.DoesNotThrow(() => { rentedArray[0] = 1; });
+        ArrayPool<object>.Shared.Return(rentedArray);
+    }
+
     private static string SanitizeTableName(string input)
     {
         var builder = new StringBuilder();
diff --git a/ClickHouse.Client/Copy/ClickHouseBulkCopy.cs b/ClickHouse.Client/Copy/ClickHouseBulkCopy.cs
index 5f22ec67..97de3bbf 100644
--- a/ClickHouse.Client/Copy/ClickHouseBulkCopy.cs
+++ b/ClickHouse.Client/Copy/ClickHouseBulkCopy.cs
@@ -218,7 +218,7 @@ private IEnumerable<Batch> IntoBatches(IEnumerable<object[]> rows, string query,
     // Convenience argument collection
     private struct Batch : IDisposable
     {
-        public object[] Rows;
+        public object[][] Rows;
         public int Size;
         public string Query;
         public ClickHouseType[] Types;
@@ -227,7 +227,7 @@ public void Dispose()
         {
             if (Rows != null)
             {
-                ArrayPool<object>.Shared.Return(Rows);
+                ArrayPool<object[]>.Shared.Return(Rows);
                 Rows = null;
             }
         }