1 files changed, 118 insertions, 0 deletions
diff --git a/spec/lib/gitlab/database/migrations/swap_columns_default_spec.rb b/spec/lib/gitlab/database/migrations/swap_columns_default_spec.rb
new file mode 100644
index 00000000000..e53480d453e
--- /dev/null
+++ b/spec/lib/gitlab/database/migrations/swap_columns_default_spec.rb
@@ -0,0 +1,118 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Database::Migrations::SwapColumnsDefault, feature_category: :database do
+  describe '#execute' do
+    let(:connection) { ApplicationRecord.connection }
+    let(:migration_context) do
+      Gitlab::Database::Migration[2.1]
+        .new('name', 'version')
+        .extend(Gitlab::Database::MigrationHelpers::Swapping)
+    end
+
+    let(:table) { :_test_swap_columns_and_defaults }
+    let(:column1) { :integer_column }
+    let(:column2) { :bigint_column }
+
+    subject(:execute_service) do
+      described_class.new(
+        migration_context: migration_context,
+        table: table,
+        column1: column1,
+        column2: column2
+      ).execute
+    end
+
+    before do
+      connection.execute(sql)
+    end
+
+    context 'when defaults are static values' do
+      let(:sql) do
+        <<~SQL
+          CREATE TABLE #{table} (
+            id integer NOT NULL,
+            #{column1} integer DEFAULT 8 NOT NULL,
+            #{column2} bigint DEFAULT 100 NOT NULL
+          );
+        SQL
+      end
+
+      it 'swaps the default correctly' do
+        expect { execute_service }
+          .to change { find_column_by(column1).default }.to('100')
+          .and change { find_column_by(column2).default }.to('8')
+          .and not_change { find_column_by(column1).default_function }.from(nil)
+          .and not_change { find_column_by(column2).default_function }.from(nil)
+      end
+    end
+
+    context 'when default is sequence' do
+      let(:sql) do
+        <<~SQL
+          CREATE TABLE #{table} (
+            id integer NOT NULL,
+            #{column1} integer NOT NULL,
+            #{column2} bigint DEFAULT 100 NOT NULL
+          );
+
+          CREATE SEQUENCE #{table}_seq
+            START WITH 1
+            INCREMENT BY 1
+            NO MINVALUE
+            NO MAXVALUE
+            CACHE 1;
+
+          ALTER SEQUENCE #{table}_seq OWNED BY #{table}.#{column1};
+          ALTER TABLE ONLY #{table} ALTER COLUMN #{column1} SET DEFAULT nextval('#{table}_seq'::regclass);
+        SQL
+      end
+
+      it 'swaps the default correctly' do
+        recorder = nil
+        expect { recorder = ActiveRecord::QueryRecorder.new { execute_service } }
+          .to change { find_column_by(column1).default }.to('100')
+          .and change { find_column_by(column1).default_function }.to(nil)
+          .and change { find_column_by(column2).default }.to(nil)
+          .and change {
+            find_column_by(column2).default_function
+          }.to("nextval('_test_swap_columns_and_defaults_seq'::regclass)")
+        expect(recorder.log).to include(
+          /SEQUENCE "_test_swap_columns_and_defaults_seq" OWNED BY "_test_swap_columns_and_defaults"."bigint_column"/
+        )
+        expect(recorder.log).to include(
+          /COLUMN "bigint_column" SET DEFAULT nextval\('_test_swap_columns_and_defaults_seq'::regclass\)/
+        )
+      end
+    end
+
+    context 'when defaults are the same' do
+      let(:sql) do
+        <<~SQL
+          CREATE TABLE #{table} (
+            id integer NOT NULL,
+            #{column1} integer DEFAULT 100 NOT NULL,
+            #{column2} bigint DEFAULT 100 NOT NULL
+          );
+        SQL
+      end
+
+      it 'does nothing' do
+        recorder = nil
+        expect { recorder = ActiveRecord::QueryRecorder.new { execute_service } }
+          .to not_change { find_column_by(column1).default }
+          .and not_change { find_column_by(column1).default_function }
+          .and not_change { find_column_by(column2).default }
+          .and not_change { find_column_by(column2).default_function }
+        expect(recorder.log).not_to include(/ALTER TABLE/)
+      end
+    end
+
+    private
+
+    def find_column_by(name)
+      connection.columns(table).find { |c| c.name == name.to_s }
+    end
+  end
+end