Raise `TransactionTimeout` when lock wait timeout exceeded for PG adapter

Follow up of #30360.

4 files changed, 35 insertions, 3 deletions

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index e6a41ec281..34ef5c79e1 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -144,8 +144,8 @@
 
     *Jeremy Green*
 
-*   Add new error class `TransactionTimeout` for MySQL adapter which will be raised
-    when lock wait time expires.
+*   Add new error class `TransactionTimeout` which will be raised
+    when lock wait timeout exceeded.
 
     *Gabriel Courtemanche*
 
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 2c3c1df2a9..46863c41ab 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -391,6 +391,7 @@ module ActiveRecord
         UNIQUE_VIOLATION      = "23505"
         SERIALIZATION_FAILURE = "40001"
         DEADLOCK_DETECTED     = "40P01"
+        LOCK_NOT_AVAILABLE    = "55P03"
 
         def translate_exception(exception, message)
           return exception unless exception.respond_to?(:result)
@@ -410,6 +411,8 @@ module ActiveRecord
             SerializationFailure.new(message)
           when DEADLOCK_DETECTED
             Deadlocked.new(message)
+          when LOCK_NOT_AVAILABLE
+            TransactionTimeout.new(message)
           else
             super
           end
diff --git a/activerecord/test/cases/adapters/mysql2/transaction_test.rb b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
index 7b032fed6d..ac9a8d9dfb 100644
--- a/activerecord/test/cases/adapters/mysql2/transaction_test.rb
+++ b/activerecord/test/cases/adapters/mysql2/transaction_test.rb
@@ -60,7 +60,7 @@ module ActiveRecord
       end
     end
 
-    test "raises TransactionTimeout when mysql raises ER_LOCK_WAIT_TIMEOUT" do
+    test "raises TransactionTimeout when lock wait timeout exceeded" do
       assert_raises(ActiveRecord::TransactionTimeout) do
         s = Sample.create!(value: 1)
         latch1 = Concurrent::CountDownLatch.new
diff --git a/activerecord/test/cases/adapters/postgresql/transaction_test.rb b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
index f56adf4a5e..b6aec8e993 100644
--- a/activerecord/test/cases/adapters/postgresql/transaction_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/transaction_test.rb
@@ -91,6 +91,35 @@ module ActiveRecord
       end
     end
 
+    test "raises TransactionTimeout when lock wait timeout exceeded" do
+      skip unless ActiveRecord::Base.connection.postgresql_version >= 90300
+      assert_raises(ActiveRecord::TransactionTimeout) do
+        s = Sample.create!(value: 1)
+        latch1 = Concurrent::CountDownLatch.new
+        latch2 = Concurrent::CountDownLatch.new
+
+        thread = Thread.new do
+          Sample.transaction do
+            Sample.lock.find(s.id)
+            latch1.count_down
+            latch2.wait
+          end
+        end
+
+        begin
+          Sample.transaction do
+            latch1.wait
+            Sample.connection.execute("SET lock_timeout = 1")
+            Sample.lock.find(s.id)
+          end
+        ensure
+          Sample.connection.execute("SET lock_timeout = DEFAULT")
+          latch2.count_down
+          thread.join
+        end
+      end
+    end
+
     private
 
       def with_warning_suppression