Add an index for user_id on all roles tables (#4268)

Currently there is only a combined index (space/org_id + user_id) which
cannot be used when accessing the table via user_id. Multiple role
queries could benefit from a dedicated index on user_id.

MySQL already has this index (for the foreign key constraint).

Author: philippthun

Diff for: db/migrations/20250318112800_add_user_id_index_to_roles_tables.rb

@@ -0,0 +1,40 @@
+Sequel.migration do
+  roles_tables = %w[
+    organizations_auditors
+    organizations_billing_managers
+    organizations_managers
+    organizations_users
+    spaces_auditors
+    spaces_developers
+    spaces_managers
+    spaces_supporters
+  ]
+
+  # adding an index concurrently cannot be done within a transaction
+  no_transaction
+
+  up do
+    roles_tables.each do |table|
+      # MySQL already has an index on user_id (foreign key constraint)
+      next unless database_type == :postgres
+
+      table_sym = table.to_sym
+      index_sym = :"#{table}_user_id_index"
+      VCAP::Migration.with_concurrent_timeout(self) do
+        add_index table_sym, :user_id, name: index_sym, if_not_exists: true, concurrently: true
+      end
+    end
+  end
+
+  down do
+    roles_tables.each do |table|
+      next unless database_type == :postgres
+
+      table_sym = table.to_sym
+      index_sym = :"#{table}_user_id_index"
+      VCAP::Migration.with_concurrent_timeout(self) do
+        drop_index table_sym, :user_id, name: index_sym, if_exists: true, concurrently: true
+      end
+    end
+  end
+end

Diff for: spec/migrations/20250318112800_add_user_id_index_to_roles_tables_spec.rb

@@ -0,0 +1,76 @@
+require 'spec_helper'
+require 'migrations/helpers/migration_shared_context'
+
+RSpec.shared_examples 'adding an index for table' do |table|
+  describe "#{table} table" do
+    let(:table_sym) { table.to_sym }
+    let(:index_sym) { :"#{table}_user_id_index" }
+
+    before do
+      skip unless db.database_type == :postgres
+    end
+
+    describe 'up migration' do
+      context 'index does not exist' do
+        it 'adds the index' do
+          expect(db.indexes(table_sym)).not_to include(index_sym)
+          expect { Sequel::Migrator.run(db, migrations_path, target: current_migration_index, allow_missing_migration_files: true) }.not_to raise_error
+          expect(db.indexes(table_sym)).to include(index_sym)
+        end
+      end
+
+      context 'index already exists' do
+        before do
+          db.add_index table_sym, :user_id, name: index_sym
+        end
+
+        it 'does not fail' do
+          expect(db.indexes(table_sym)).to include(index_sym)
+          expect { Sequel::Migrator.run(db, migrations_path, target: current_migration_index, allow_missing_migration_files: true) }.not_to raise_error
+          expect(db.indexes(table_sym)).to include(index_sym)
+        end
+      end
+    end
+
+    describe 'down migration' do
+      before do
+        Sequel::Migrator.run(db, migrations_path, target: current_migration_index, allow_missing_migration_files: true)
+      end
+
+      context 'index exists' do
+        it 'removes the index' do
+          expect(db.indexes(table_sym)).to include(index_sym)
+          expect { Sequel::Migrator.run(db, migrations_path, target: current_migration_index - 1, allow_missing_migration_files: true) }.not_to raise_error
+          expect(db.indexes(table_sym)).not_to include(index_sym)
+        end
+      end
+
+      context 'index does not exist' do
+        before do
+          db.drop_index table_sym, :user_id, name: index_sym
+        end
+
+        it 'does not fail' do
+          expect(db.indexes(table_sym)).not_to include(index_sym)
+          expect { Sequel::Migrator.run(db, migrations_path, target: current_migration_index - 1, allow_missing_migration_files: true) }.not_to raise_error
+          expect(db.indexes(table_sym)).not_to include(index_sym)
+        end
+      end
+    end
+  end
+end
+
+RSpec.describe 'migration to add an index for user_id on all roles tables', isolation: :truncation, type: :migration do
+  include_context 'migration' do
+    let(:migration_filename) { '20250318112800_add_user_id_index_to_roles_tables.rb' }
+  end
+
+  include_examples 'adding an index for table', 'organizations_auditors'
+  include_examples 'adding an index for table', 'organizations_billing_managers'
+  include_examples 'adding an index for table', 'organizations_managers'
+  include_examples 'adding an index for table', 'organizations_users'
+  include_examples 'adding an index for table', 'spaces_auditors'
+  include_examples 'adding an index for table', 'spaces_developers'
+  include_examples 'adding an index for table', 'spaces_managers'
+  include_examples 'adding an index for table', 'spaces_supporters'
+end