Connection Mode (Session Mode)

  • Each client maintains a dedicated connection to the database for the entire session duration[2].
  • The connection is only released back to the pool when the client disconnects from the database[2].
  • This mode replicates a direct connection to PostgreSQL and supports all PostgreSQL features and mechanisms[2].
  • It’s safer and more compatible with all PostgreSQL clients[2].
  • Does not significantly reduce the load on database resources[2].

Transaction Mode

  • The connection to PostgreSQL is maintained only for the duration of a transaction[2].
  • When the transaction completes, the connection is returned to the pool and can be reused by other clients[2].
  • Allows for a higher number of client connections (up to 10,000) with a smaller pool size[2].
  • Reduces the load on DBMS resources, especially beneficial for a large number of low-load client connections[2].
  • More efficient in terms of resource utilization, as idle connections are released back to the pool[3].

Key Differences

  1. Connection Duration:

    • Connection mode: Entire session
    • Transaction mode: Only for the duration of a transaction

  2. Resource Efficiency:

    • Connection mode: Less efficient, as connections are held even when idle
    • Transaction mode: More efficient, as connections are released when not in an active transaction

  3. Feature Compatibility:

    • Connection mode: Supports all PostgreSQL features
    • Transaction mode: Has limitations on certain features like prepared statements, advisory locks, and some session-level commands[2][3]

  4. Scalability:

    • Connection mode: Limited by the number of actual database connections
    • Transaction mode: Can handle more client connections with fewer actual database connections

  5. Use Case:

    • Connection mode: Better for applications that require persistent connections or use session-level features
    • Transaction mode: Ideal for applications with many short-lived database interactions or those that primarily use transactional operations

  6. Performance:

    • Transaction mode generally offers better performance and scalability for high-concurrency scenarios[4]

  7. Behavior Consistency:

    • Connection mode: Behaves more like a direct database connection
    • Transaction mode: May require changes in application behavior to account for connection sharing[3]

When choosing between these modes, consider your application’s specific requirements, the nature of your database interactions, and the need for scalability versus feature compatibility.

Conclusion

  • Connection Mode:

    • Better for applications that require persistent connections or use session-level features.
    • Safer and more compatible with all PostgreSQL clients.
    • Supports all PostgreSQL features and mechanisms.

  • Transaction Mode:

    • Ideal for applications with many short-lived database interactions or those that primarily use transactional operations.
    • More efficient in terms of resource utilization.
    • Allows for a higher number of client connections with a smaller pool size.

Citations