Is Email Address a Suboptimal Primary Key Choice?

While designing a web application, you may encounter the dilemma of selecting a primary key for a user table. Email addresses are commonly considered for this role due to their uniqueness. However, concerns arise regarding their suitability relative to auto-incrementing numbers.

Comparison Speed

Your colleague's assertion that string comparisons are slower than integer comparisons is valid. This aspect particularly matters if you intend to execute complex queries with multiple joins. String comparisons are computationally more intensive than integer comparisons, potentially slowing query execution time.

Storage Considerations

When storing user information across multiple tables, foreign keys referencing the user table will contain the email address. Consequently, email addresses may be repeated multiple times, leading to potential storage inefficiencies.

Best Practices for Primary Key Selection

While string comparisons can be slower than integer comparisons, the performance gap may not be significant for simple user retrievals. However, if complex queries with joins are anticipated, an auto-incrementing integer primary key might be more efficient. Furthermore, consider the data storage implications to minimize redundant email address storage.

In the context of PostgreSQL, email addresses as primary keys face a caveat. PostgreSQL does not truncate email addresses by default, which can lead to inconsistent data. To mitigate this, you may opt for a different primary key strategy, such as an auto-incrementing integer or a unique hash of the email address.