Merge branch 'migration-helpers' into 'master'

Added helper methods for database migrations

These helpers can ultimately be used to write migrations that don't
require downtime.

See #15464 for more information.

See merge request !3860

1 files changed, 124 insertions, 0 deletions

diff --git a/spec/lib/gitlab/database/migration_helpers_spec.rb b/spec/lib/gitlab/database/migration_helpers_spec.rb
new file mode 100644
index 00000000000..ec43165bb53
--- /dev/null
+++ b/spec/lib/gitlab/database/migration_helpers_spec.rb
@@ -0,0 +1,124 @@
+require 'spec_helper'
+
+describe Gitlab::Database::MigrationHelpers, lib: true do
+  let(:model) do
+    Class.new do
+      include Gitlab::Database::MigrationHelpers
+
+      def method_missing(name, *args, &block)
+        ActiveRecord::Base.connection.send(name, *args, &block)
+      end
+    end.new
+  end
+
+  describe '#add_concurrent_index' do
+    context 'outside a transaction' do
+      before do
+        expect(model).to receive(:transaction_open?).and_return(false)
+      end
+
+      context 'using PostgreSQL' do
+        it 'creates the index concurrently' do
+          expect(Gitlab::Database).to receive(:postgresql?).and_return(true)
+
+          expect(model).to receive(:add_index).
+            with(:users, :foo, algorithm: :concurrently)
+
+          model.add_concurrent_index(:users, :foo)
+        end
+      end
+
+      context 'using MySQL' do
+        it 'creates a regular index' do
+          expect(Gitlab::Database).to receive(:postgresql?).and_return(false)
+
+          expect(model).to receive(:add_index).
+            with(:users, :foo)
+
+          model.add_concurrent_index(:users, :foo)
+        end
+      end
+    end
+
+    context 'inside a transaction' do
+      it 'raises RuntimeError' do
+        expect(model).to receive(:transaction_open?).and_return(true)
+
+        expect { model.add_concurrent_index(:users, :foo) }.
+          to raise_error(RuntimeError)
+      end
+    end
+  end
+
+  describe '#update_column_in_batches' do
+    before do
+      create_list(:empty_project, 5)
+    end
+
+    it 'updates all the rows in a table' do
+      model.update_column_in_batches(:projects, :import_error, 'foo')
+
+      expect(Project.where(import_error: 'foo').count).to eq(5)
+    end
+  end
+
+  describe '#add_column_with_default' do
+    context 'outside of a transaction' do
+      before do
+        expect(model).to receive(:transaction_open?).and_return(false)
+
+        expect(model).to receive(:transaction).twice.and_yield
+
+        expect(model).to receive(:add_column).
+          with(:projects, :foo, :integer, default: nil)
+
+        expect(model).to receive(:change_column_default).
+          with(:projects, :foo, 10)
+      end
+
+      it 'adds the column while allowing NULL values' do
+        expect(model).to receive(:update_column_in_batches).
+          with(:projects, :foo, 10)
+
+        expect(model).not_to receive(:change_column_null)
+
+        model.add_column_with_default(:projects, :foo, :integer,
+                                      default: 10,
+                                      allow_null: true)
+      end
+
+      it 'adds the column while not allowing NULL values' do
+        expect(model).to receive(:update_column_in_batches).
+          with(:projects, :foo, 10)
+
+        expect(model).to receive(:change_column_null).
+          with(:projects, :foo, false)
+
+        model.add_column_with_default(:projects, :foo, :integer, default: 10)
+      end
+
+      it 'removes the added column whenever updating the rows fails' do
+        expect(model).to receive(:update_column_in_batches).
+          with(:projects, :foo, 10).
+          and_raise(RuntimeError)
+
+        expect(model).to receive(:remove_column).
+          with(:projects, :foo)
+
+        expect do
+          model.add_column_with_default(:projects, :foo, :integer, default: 10)
+        end.to raise_error(RuntimeError)
+      end
+    end
+
+    context 'inside a transaction' do
+      it 'raises RuntimeError' do
+        expect(model).to receive(:transaction_open?).and_return(true)
+
+        expect do
+          model.add_column_with_default(:projects, :foo, :integer, default: 10)
+        end.to raise_error(RuntimeError)
+      end
+    end
+  end
+end