Checking for already present data before commiting?

I'm following a simple youtube course on how to build a FastAPI app with a Postgres db. The Users table has the following schema (using SQLAlchemy): class User(Base): """ Class responsible for the users table in the PostgreSQL DB """ __tablename__ = "users" id = Column(Integer, primary_key=True, index=True, nullable=False) email = Column(String, unique=True, nullable=False) password = Column(String, nullable=False) created_at = Column(TIMESTAMP(timezone=True), nullable=False, server_default=text("now()")) I've noticed that when I try to create a user (a row in a table) with an already used mail, I get an error, which is expected. Then, if I change the mail to a different one, and commit again the change, all is fine... However, when I check in the table for all the elements, I see that the id column has skipped some values, corresponding to those tries for which I got sqlalchemy.exc.IntegrityError. Given this situation, I wonder whether it's better to first check for an already existing mail, and only then try to commit... otherwise, the id column will have jumps in its values.