From c6ae06e1d32b354715f908d723164149e4a02cdb Mon Sep 17 00:00:00 2001
From: Eric Scouten <eric@scouten.com>
Date: Thu, 19 Sep 2019 12:43:08 -0700
Subject: [PATCH 1/2] Try wrapping an explicit transaction around the update
 query.

---
 bench/update_item_sql.exs | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/bench/update_item_sql.exs b/bench/update_item_sql.exs
index 2b8b68e..6236b01 100644
--- a/bench/update_item_sql.exs
+++ b/bench/update_item_sql.exs
@@ -30,16 +30,19 @@ ParallelBench.run(
     random_item_id = Enum.random(item_ids)
     random = :rand.uniform(100_000_000_000_000)
 
-    {:ok, %{num_rows: 1}} =
-      SQL.query(
-        Repo,
-        """
-        UPDATE items
-        SET mumble3 = $1
-        WHERE id = $2;
-        """,
-        ["New Mumble #{random}", random_item_id]
-      )
+    {:ok, _} =
+      Repo.transaction(fn ->
+        {:ok, %{num_rows: 1}} =
+          SQL.query(
+            Repo,
+            """
+            UPDATE items
+            SET mumble3 = $1
+            WHERE id = $2;
+            """,
+            ["New Mumble #{random}", random_item_id]
+          )
+      end)
   end,
   parallel: 10,
   duration: 10

From a338b3d8d0f569bef1b956b276b28208fe1f01ae Mon Sep 17 00:00:00 2001
From: Eric Scouten <eric@scouten.com>
Date: Thu, 19 Sep 2019 12:53:44 -0700
Subject: [PATCH 2/2] Try suggestion of using transaction isolation level.

---
 bench/update_item_sql.exs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bench/update_item_sql.exs b/bench/update_item_sql.exs
index 6236b01..97ddcf5 100644
--- a/bench/update_item_sql.exs
+++ b/bench/update_item_sql.exs
@@ -32,6 +32,8 @@ ParallelBench.run(
 
     {:ok, _} =
       Repo.transaction(fn ->
+        SQL.query!(Repo, "SET TRANSACTION ISOLATION LEVEL REPEATABLE READ;")
+
         {:ok, %{num_rows: 1}} =
           SQL.query(
             Repo,