From 1d5d9b41b2b32407f06a69d5697c7a639d12216d Mon Sep 17 00:00:00 2001
From: Abdelkader Boudih <seuros@pre-history.com>
Date: Mon, 12 Feb 2024 01:39:08 +0100
Subject: [PATCH] chore: Refactor and optimize MySQL advisory lock handling

This commit removes unused MySQL lock variables,
---
 Makefile                               | 14 ++++++++++++++
 docker-compose.yml                     | 20 ++++++++++++++++++++
 lib/with_advisory_lock/mysql.rb        | 14 ++++++++------
 test/with_advisory_lock/shared_test.rb |  4 ++--
 test/with_advisory_lock/thread_test.rb |  4 ++--
 5 files changed, 46 insertions(+), 10 deletions(-)
 create mode 100644 Makefile
 create mode 100644 docker-compose.yml

diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..dc1fe05
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,14 @@
+.PHONY: test-pg test-mysql
+
+test-pg:
+	docker compose up -d pg
+	sleep 10 # give some time for the service to start
+	DATABASE_URL=postgres://with_advisory:with_advisory_pass@localhost/with_advisory_lock_test appraisal activerecord-7.1 rake test
+
+test-mysql:
+	docker compose up -d mysql
+	sleep 10 # give some time for the service to start
+	DATABASE_URL=mysql2://with_advisory:with_advisory_pass@0.0.0.0:3306/with_advisory_lock_test appraisal activerecord-7.1 rake test
+
+
+test: test-pg test-mysql
diff --git a/docker-compose.yml b/docker-compose.yml
new file mode 100644
index 0000000..2440305
--- /dev/null
+++ b/docker-compose.yml
@@ -0,0 +1,20 @@
+version: "3.9"
+services:
+  pg:
+    image: postgres:16
+    environment:
+      POSTGRES_USER: with_advisory
+      POSTGRES_PASSWORD: with_advisory_pass
+      POSTGRES_DB: with_advisory_lock_test
+    ports:
+      - "5432:5432"
+  mysql:
+    image: mysql:8
+    environment:
+      MYSQL_USER: with_advisory
+      MYSQL_PASSWORD: with_advisory_pass
+      MYSQL_DATABASE: with_advisory_lock_test
+      MYSQL_RANDOM_ROOT_PASSWORD: "yes"
+      MYSQL_ROOT_HOST: '%'
+    ports:
+      - "3306:3306"
diff --git a/lib/with_advisory_lock/mysql.rb b/lib/with_advisory_lock/mysql.rb
index bdb35e7..3ca8ef9 100644
--- a/lib/with_advisory_lock/mysql.rb
+++ b/lib/with_advisory_lock/mysql.rb
@@ -2,10 +2,8 @@
 
 module WithAdvisoryLock
   class MySQL < Base
-    # Caches nested lock support by MySQL reported version
-    @@mysql_nl_cache       = {}
-    @@mysql_nl_cache_mutex = Mutex.new
-    # See https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
+    # See https://dev.mysql.com/doc/refman/5.7/en/locking-functions.html
+    # See https://dev.mysql.com/doc/refman/8.0/en/locking-functions.html
     def try_lock
       raise ArgumentError, 'shared locks are not supported on MySQL' if shared
       raise ArgumentError, 'transaction level locks are not supported on MySQL' if transaction
@@ -18,8 +16,12 @@ def release_lock
     end
 
     def execute_successful?(mysql_function)
-      sql = "SELECT #{mysql_function} AS #{unique_column_name}"
-      connection.select_value(sql).to_i.positive?
+      execute_query(mysql_function) == 1
+    end
+
+    def execute_query(mysql_function)
+      sql = "SELECT #{mysql_function}"
+      connection.query_value(sql)
     end
 
     # MySQL wants a string as the lock key.
diff --git a/test/with_advisory_lock/shared_test.rb b/test/with_advisory_lock/shared_test.rb
index 7cd23a4..f2b0ba1 100644
--- a/test/with_advisory_lock/shared_test.rb
+++ b/test/with_advisory_lock/shared_test.rb
@@ -24,7 +24,7 @@ def cleanup!
   private
 
   def work
-    ApplicationRecord.connection_pool.with_connection do
+    Tag.connection_pool.with_connection do
       Tag.with_advisory_lock('test', timeout_seconds: 0, shared: @shared) do
         @locked = true
         sleep 0.01 until @cleanup
@@ -117,7 +117,7 @@ class PostgreSQLTest < SupportedEnvironmentTest
     end
 
     def pg_lock_modes
-      ApplicationRecord.connection.select_values("SELECT mode FROM pg_locks WHERE locktype = 'advisory';")
+      Tag.connection.select_values("SELECT mode FROM pg_locks WHERE locktype = 'advisory';")
     end
 
     test 'allows shared lock to be upgraded to an exclusive lock' do
diff --git a/test/with_advisory_lock/thread_test.rb b/test/with_advisory_lock/thread_test.rb
index 2c86be0..4e00f27 100644
--- a/test/with_advisory_lock/thread_test.rb
+++ b/test/with_advisory_lock/thread_test.rb
@@ -10,7 +10,7 @@ class SeparateThreadTest < GemTestCase
     @t1_return_value = nil
 
     @t1 = Thread.new do
-      ApplicationRecord.connection_pool.with_connection do
+      Label.connection_pool.with_connection do
         @t1_return_value = Label.with_advisory_lock(@lock_name) do
           @mutex.synchronize { @t1_acquired_lock = true }
           sleep
@@ -21,7 +21,7 @@ class SeparateThreadTest < GemTestCase
 
     # Wait for the thread to acquire the lock:
     sleep(0.1) until @mutex.synchronize { @t1_acquired_lock }
-    ApplicationRecord.connection.reconnect!
+    Label.connection.reconnect!
   end
 
   teardown do