From ccdf74e2187d4f66f3cbef1957da74c556ed4f3d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pedro=20Pi=C3=B1era=20Buend=C3=ADa?= <pedro@pepicrft.me>
Date: Mon, 20 Apr 2026 14:39:51 +0200
Subject: [PATCH 1/2] Add Ecto transaction callbacks

---
 lib/ecto/adapters/clickhouse.ex | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/lib/ecto/adapters/clickhouse.ex b/lib/ecto/adapters/clickhouse.ex
index 3c4554a..44d6f38 100644
--- a/lib/ecto/adapters/clickhouse.ex
+++ b/lib/ecto/adapters/clickhouse.ex
@@ -29,6 +29,7 @@ defmodule Ecto.Adapters.ClickHouse do
   @behaviour Ecto.Adapter.Schema
   @behaviour Ecto.Adapter.Storage
   @behaviour Ecto.Adapter.Structure
+  @behaviour Ecto.Adapter.Transaction
 
   @conn __MODULE__.Connection
   @driver :ch
@@ -160,6 +161,21 @@ defmodule Ecto.Adapters.ClickHouse do
     Ecto.Adapters.SQL.checked_out?(meta)
   end
 
+  @impl Ecto.Adapter.Transaction
+  def transaction(adapter_meta, opts, callback) do
+    Ecto.Adapters.SQL.transaction(adapter_meta, opts, callback)
+  end
+
+  @impl Ecto.Adapter.Transaction
+  def in_transaction?(%{pid: pool}) do
+    Ecto.Adapters.SQL.in_transaction?(%{pid: pool})
+  end
+
+  @impl Ecto.Adapter.Transaction
+  def rollback(adapter_meta, value) do
+    Ecto.Adapters.SQL.rollback(adapter_meta, value)
+  end
+
   @impl Ecto.Adapter
   def dumpers(:uuid, Ecto.UUID), do: [&__MODULE__.hex_uuid/1]
   def dumpers(:uuid, type), do: [type, &__MODULE__.hex_uuid/1]

From 4554ec285a5925ec26128d690c0241cc644fd4fc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Pedro=20Pi=C3=B1era=20Buend=C3=ADa?= <pedro@pepicrft.me>
Date: Mon, 20 Apr 2026 14:55:17 +0200
Subject: [PATCH 2/2] Add transaction callback tests

---
 test/ecto/adapters/clickhouse_test.exs | 60 ++++++++++++++++++++++++++
 1 file changed, 60 insertions(+)

diff --git a/test/ecto/adapters/clickhouse_test.exs b/test/ecto/adapters/clickhouse_test.exs
index c66c69e..31d6f23 100644
--- a/test/ecto/adapters/clickhouse_test.exs
+++ b/test/ecto/adapters/clickhouse_test.exs
@@ -2,6 +2,8 @@ defmodule Ecto.Adapters.ClickHouseTest do
   use ExUnit.Case
 
   alias Ecto.Adapters.ClickHouse
+  alias Ecto.Integration.TestRepo
+  import ExUnit.CaptureLog
 
   describe "storage_up/1" do
     test "create database" do
@@ -61,4 +63,62 @@ defmodule Ecto.Adapters.ClickHouseTest do
       assert ClickHouse.storage_status(opts) == :up
     end
   end
+
+  describe "transaction callbacks" do
+    test "in_transaction?/1 is false for an idle checked out connection" do
+      TestRepo.checkout(fn ->
+        meta = Ecto.Adapter.lookup_meta(TestRepo.get_dynamic_repo())
+        refute ClickHouse.in_transaction?(meta)
+      end)
+    end
+
+    test "transaction/3 uses the checked out transactional connection" do
+      with_transaction_connection(fn meta ->
+        assert {:ok, :inside_transaction} =
+                 ClickHouse.transaction(meta, [], fn ->
+                   assert ClickHouse.in_transaction?(meta)
+                   :inside_transaction
+                 end)
+      end)
+    end
+
+    test "rollback/2 aborts the checked out transactional connection" do
+      capture_log(fn ->
+        with_transaction_connection(fn meta ->
+          assert {:error, :rolled_back} =
+                   ClickHouse.transaction(meta, [], fn ->
+                     assert ClickHouse.in_transaction?(meta)
+                     ClickHouse.rollback(meta, :rolled_back)
+                   end)
+        end)
+      end)
+    end
+
+    test "rollback/2 raises outside a transaction" do
+      TestRepo.checkout(fn ->
+        meta = Ecto.Adapter.lookup_meta(TestRepo.get_dynamic_repo())
+
+        assert_raise RuntimeError, "cannot call rollback outside of transaction", fn ->
+          ClickHouse.rollback(meta, :rolled_back)
+        end
+      end)
+    end
+  end
+
+  defp with_transaction_connection(fun) do
+    TestRepo.checkout(fn ->
+      meta = Ecto.Adapter.lookup_meta(TestRepo.get_dynamic_repo())
+      key = sql_conn_key(meta.pid)
+      conn = Process.get(key)
+      Process.put(key, %{conn | conn_mode: :transaction})
+
+      try do
+        fun.(meta)
+      after
+        Process.put(key, conn)
+      end
+    end)
+  end
+
+  defp sql_conn_key(pool), do: {Ecto.Adapters.SQL, pool}
 end