ALTER TABLE users
  ADD COLUMN IF NOT EXISTS google_sub TEXT,
  ADD COLUMN IF NOT EXISTS google_email TEXT NOT NULL DEFAULT '',
  ADD COLUMN IF NOT EXISTS google_name TEXT NOT NULL DEFAULT '',
  ADD COLUMN IF NOT EXISTS google_avatar_url TEXT NOT NULL DEFAULT '',
  ADD COLUMN IF NOT EXISTS google_linked_at TIMESTAMPTZ;

CREATE UNIQUE INDEX IF NOT EXISTS users_google_sub_unique_idx
  ON users (google_sub)
  WHERE google_sub IS NOT NULL;

CREATE INDEX IF NOT EXISTS users_google_email_idx
  ON users (google_email)
  WHERE google_email <> '';