lib: add migration helpers for making a column unique

spec/lib/database/migration_helpers_spec.rb

@@ -0,0 +1,133 @@
+describe Database::MigrationHelpers do
+  class TestLabel < ApplicationRecord
+  end
+
+  before(:all) do
+    ActiveRecord::Migration.suppress_messages do
+      ActiveRecord::Migration.create_table "test_labels", force: true do |t|
+        t.string :label
+        t.integer :user_id
+      end
+    end
+  end
+
+  before(:each) do
+    # User 1 labels
+    TestLabel.create({ id: 1, label: 'Important', user_id: 1 })
+    TestLabel.create({ id: 2, label: 'Urgent', user_id: 1 })
+    TestLabel.create({ id: 3, label: 'Done', user_id: 1 })
+    TestLabel.create({ id: 4, label: 'Bug', user_id: 1 })
+
+    # User 2 labels
+    TestLabel.create({ id: 5, label: 'Important', user_id: 2 })
+    TestLabel.create({ id: 6, label: 'Critical', user_id: 2 })
+
+    # Duplicates
+    TestLabel.create({ id: 7, label: 'Urgent', user_id: 1 })
+    TestLabel.create({ id: 8, label: 'Important', user_id: 2 })
+  end
+
+  after(:all) do
+    ActiveRecord::Migration.suppress_messages do
+      ActiveRecord::Migration.drop_table :test_labels, force: true
+    end
+  end
+
+  let(:model) { ActiveRecord::Migration.new.extend(Database::MigrationHelpers) }
+
+  describe '.find_duplicates' do
+    context 'using a single column for uniqueness' do
+      subject do
+        model.find_duplicates(:test_labels, [:label])
+      end
+
+      it 'finds duplicates' do
+        expect(subject.length).to eq 2
+      end
+
+      it 'finds three labels with "Important"' do
+        expect(subject).to include [1, 5, 8]
+      end
+
+      it 'finds two labels with "Urgent"' do
+        expect(subject).to include [2, 7]
+      end
+    end
+
+    context 'using multiple columns for uniqueness' do
+      subject do
+        model.find_duplicates(:test_labels, [:label, :user_id])
+      end
+
+      it 'finds duplicates' do
+        expect(subject.length).to eq 2
+      end
+
+      it 'finds two labels with "Important" for user 2' do
+        expect(subject).to include [5, 8]
+      end
+
+      it 'finds two labels with "Urgent" for user 1' do
+        expect(subject).to include [2, 7]
+      end
+    end
+  end
+
+  describe '.delete_duplicates' do
+    subject do
+      model.delete_duplicates(:test_labels, [:label])
+    end
+
+    it 'keeps the first item, and delete the others' do
+      expect { subject }.to change(TestLabel, :count).by(-3)
+      expect(TestLabel.where(label: 'Critical').count).to eq(1)
+      expect(TestLabel.where(label: 'Important').count).to eq(1)
+      expect(TestLabel.where(label: 'Urgent').count).to eq(1)
+      expect(TestLabel.where(label: 'Bug').count).to eq(1)
+      expect(TestLabel.where(label: 'Done').count).to eq(1)
+    end
+  end
+
+  describe '.add_concurrent_index' do
+    let(:model) { ActiveRecord::Migration.new.extend(Database::MigrationHelpers) }
+
+    context 'outside a transaction' do
+      before do
+        model.verbose = false
+        allow(model).to receive(:transaction_open?).and_return(false)
+        allow(model).to receive(:disable_statement_timeout).and_call_original
+      end
+
+      it 'creates the index concurrently' do
+        expect(model).to receive(:add_index)
+          .with(:users, :foo, algorithm: :concurrently)
+
+        model.add_concurrent_index(:users, :foo)
+      end
+
+      it 'creates unique index concurrently' do
+        expect(model).to receive(:add_index)
+          .with(:users, :foo, { algorithm: :concurrently, unique: true })
+
+        model.add_concurrent_index(:users, :foo, unique: true)
+      end
+
+      it 'does nothing if the index exists already' do
+        expect(model).to receive(:index_exists?)
+          .with(:users, :foo, { algorithm: :concurrently, unique: true }).and_return(true)
+        expect(model).not_to receive(:add_index)
+
+        model.add_concurrent_index(:users, :foo, unique: true)
+      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
+end