chore: refractor postgresql class

lib/with_advisory_lock/base.rb

@@ -56,9 +56,7 @@ def already_locked?
     def with_advisory_lock_if_needed(&block)
       if disable_query_cache
         return lock_and_yield do
-          connection.uncached do
-            yield
-          end
+          connection.uncached(&block)
         end
       end
 

lib/with_advisory_lock/postgresql.rb

@@ -1,43 +1,52 @@
 # frozen_string_literal: true
-
 module WithAdvisoryLock
   class PostgreSQL < Base
-    # See http://www.postgresql.org/docs/9.1/static/functions-admin.html#FUNCTIONS-ADVISORY-LOCKS
+    LOCK_RESULT_VALUES = ['t', true].freeze
+    LOCK_ENV_NAME = 'WITH_ADVISORY_LOCK_PREFIX'.freeze
+    PG_ADVISORY_UNLOCK = 'pg_advisory_unlock'.freeze
+    PG_TRY_ADVISORY = 'try_advisory'.freeze
+    ERROR_MESSAGE_REGEX = / ERROR: +current transaction is aborted,/
+
     def try_lock
-      pg_function = "pg_try_advisory#{transaction ? '_xact' : ''}_lock#{shared ? '_shared' : ''}"
-      execute_successful?(pg_function)
+      execute_successful?(pg_function_name(PG_TRY_ADVISORY, transaction))
     end
 
     def release_lock
       return if transaction
-
-      pg_function = "pg_advisory_unlock#{shared ? '_shared' : ''}"
-      execute_successful?(pg_function)
-    rescue ActiveRecord::StatementInvalid => e
-      raise unless e.message =~ / ERROR: +current transaction is aborted,/
-
       begin
+        execute_successful?(pg_function_name(PG_ADVISORY_UNLOCK, false))
+      rescue ActiveRecord::StatementInvalid => e
+        raise unless e.message =~ ERROR_MESSAGE_REGEX
         connection.rollback_db_transaction
-        execute_successful?(pg_function)
+        retry
       ensure
         connection.begin_db_transaction
       end
     end
 
+    def pg_function_name(base_name, transaction_scope)
+      [
+        base_name,
+        transaction_scope ? '_xact' : nil,
+        shared ? '_shared' : nil
+      ].compact.join
+    end
+
     def execute_successful?(pg_function)
+      result = connection.select_value(prepare_sql(pg_function))
+      LOCK_RESULT_VALUES.include?(result)
+    end
+
+    def prepare_sql(pg_function)
       comment = lock_name.to_s.gsub(%r{(/\*)|(\*/)}, '--')
-      sql = "SELECT #{pg_function}(#{lock_keys.join(',')}) AS #{unique_column_name} /* #{comment} */"
-      result = connection.select_value(sql)
-      # MRI returns 't', jruby returns true. YAY!
-      ['t', true].include?(result)
+      "SELECT #{pg_function}(#{lock_keys.join(',')}) AS #{unique_column_name} /* #{comment} */"
     end
 
-    # PostgreSQL wants 2 32bit integers as the lock key.
     def lock_keys
-      @lock_keys ||= [stable_hashcode(lock_name), ENV['WITH_ADVISORY_LOCK_PREFIX']].map do |ea|
-        # pg advisory args must be 31 bit ints
-        ea.to_i & 0x7fffffff
-      end
+      @lock_keys ||= [
+        stable_hashcode(lock_name),
+        ENV[LOCK_ENV_NAME]
+      ].map { |ea| ea.to_i & 0x7fffffff }
     end
   end
 end