Add raise InvalidSequenceId

- Error in case of forget insert sequencer record

lib/active_record/sharding/errors.rb

@@ -8,5 +8,8 @@ class MissingShardingKeyAttribute < Error
 
     class MissingPrimaryKey < Error
     end
+
+    class InvalidSequenceId < Error
+    end
   end
 end

lib/active_record/sharding/sequencer.rb

@@ -32,7 +32,9 @@ def current_sequence_id
 
         def next_sequence_id(offset = 1)
           raise NegativeNumberOffsetError if offset < 1
-          execute_sql "id +#{offset}"
+          sequence_id = execute_sql "id +#{offset}"
+          raise ActiveRecord::Sharding::InvalidSequenceId if sequence_id.zero?
+          sequence_id
         end
 
         def execute_sql(last_insert_id_args)

spec/active_record/sharding/sequencer_spec.rb

@@ -10,6 +10,26 @@ def self.name
     end
   end
 
+  let(:sequencer_args) do
+    { sequencer_name: "user" }
+  end
+
+  context "forget insert sequencer record" do
+    before do
+      ActiveRecord::Sharding::DatabaseTasks.drop_sequencer_database sequencer_args
+      ActiveRecord::Sharding::DatabaseTasks.create_sequencer_database sequencer_args
+      ActiveRecord::Sharding::DatabaseTasks.create_table_sequencer_database sequencer_args
+    end
+
+    after do
+      ActiveRecord::Sharding::DatabaseTasks.insert_initial_record_sequencer_database sequencer_args # forget this in setup
+    end
+
+    it "raise ActiveRecord::Sharding::InvalidSequenceId" do
+      expect { model.next_sequence_id }.to raise_error ActiveRecord::Sharding::InvalidSequenceId
+    end
+  end
+
   describe '#current_sequence_id' do
     it "returns current sequence id" do
       current_id = model.current_sequence_id