PostgreSQL 17 Tutorial

PostgreSQL 17 introduces a host of exciting features and improvements that enhance performance, usability, and scalability. This tutorial will guide you through some of the most significant updates in PostgreSQL 17, helping you make the most of the new capabilities.

Overview of PostgreSQL 17

PostgreSQL 17 includes several major enhancements, including a rewritten memory manager for VACUUM, improved JSON support, enhanced logical replication, and more efficient backup and upgrade options. Let's dive into these features and how to use them effectively.

1. VACUUM Overhaul

What's New?

PostgreSQL 17 introduces a brand-new memory manager for VACUUM, which significantly reduces RAM spikes and speeds up vacuuming of large tables. This improvement makes maintenance operations more predictable and efficient.

Benefits

• Reduced memory spikes during VACUUM operations.
• Faster vacuuming of large tables.
• Improved performance for systems with limited RAM.

Example

To vacuum a table with the new memory manager:

VACUUM (FULL) my_large_table;

The rewritten memory manager ensures that the process is more efficient and causes fewer pauses or spikes in memory usage.

2. SQL/JSON++ Features

What's New?

PostgreSQL 17 introduces several SQL/JSON++ features, including JSON_TABLE(), identity constructors, and full JSON path query support. These features make it easier to work with JSON data without resorting to PL/pgSQL hacks.

Benefits

• Shred JSON data into rows directly in SQL without custom functions.
• Improved support for JSON path queries for more precise data extraction.

Example

Given the following JSON data:

{
  "users": [
    {"name": "John Doe", "age": 30},
    {"name": "Jane Smith", "age": 25}
  ]
}

You can use JSON_TABLE() to shred the JSON into rows:

SELECT *
FROM JSON_TABLE(
  '{"users":[{"name":"John Doe","age":30},{"name":"Jane Smith","age":25}]}',
  '$.users[*]' COLUMNS (
    name TEXT PATH '$.name',
    age INT PATH '$.age'
  )
) AS users;

This will return: | name | age | |-----------|-----| | John Doe | 30 | | Jane Smith | 25 |

3. Logical Replication 2.0

What's New?

PostgreSQL 17 introduces Logical Replication 2.0, which includes built-in fail-over control, pg_createsubscriber, and improved pg_upgrade that maintains replication slots for zero-downtime switchover.

Benefits

• Simplified setup and management of logical replication.
• Zero-downtime switchover during upgrades.
• Built-in fail-over control for high availability.

Example

To create a subscriber:

SELECT pg_createsubscriber('my_subscriber', 'my_publisher');

This command simplifies the setup of logical replication subscribers.

4. Incremental Base Backups

What's New?

PostgreSQL 17 introduces incremental base backups using pg_basebackup --incremental. This feature only ships changed blocks, making it ideal for cheap and efficient long-term retention in storage systems like S3.

Benefits

• Reduced storage costs for backups.
• Faster backup and restore operations.
• Ideal for cloud-based retention solutions.

Example

To perform an incremental base backup:

pg_basebackup --incremental --pgdata=/var/lib/postgresql/data --write-recovery-conf

This command creates an incremental backup that only includes changed blocks since the last backup.

5. Security & SSL Improvements

What's New?

PostgreSQL 17 introduces the sslnegotiation=direct option, which skips unnecessary SSL negotiation round-trips for faster connections.

Benefits

• Faster SSL connections.
• Improved performance for applications with frequent connections.

Example

To enable direct SSL negotiation, update your postgresql.conf:

sslnegotiation = direct

This setting reduces the overhead of SSL negotiation, resulting in faster connection establishment.

6. Error Handling in COPY

What's New?

PostgreSQL 17 introduces COPY ... ON_ERROR ignore, which allows you to ignore errors during large data ingests and keeps the process alive.

Benefits

• Improved robustness for large-scale data imports.
• Avoid restarts due to individual invalid records.

Example

To ignore errors during a COPY operation:

COPY my_table (name, age)
FROM 'data.csv'
ON_ERROR IGNORE;

This command will skip invalid records and continue with the import process.

7. Upgrade Path

What's New?

PostgreSQL 17 supports both dump/restore and pg_upgrade for upgrades. Note that some statistics columns have been renamed, and old_snapshot_threshold has been removed.

Important Notes

• Use pg_dump and pg_restore if you prefer a dump/restore approach.
• Use pg_upgrade for in-place upgrades.
• Check your scripts for references to renamed statistics columns.

Example

To upgrade using pg_upgrade:

pg_upgrade --old-datadir=/var/lib/postgresql/old --new-datadir=/var/lib/postgresql/new

This command performs an in-place upgrade while maintaining replication slots.

Conclusion

PostgreSQL 17 brings significant improvements in performance, usability, and scalability. From the VACUUM overhaul to incremental base backups, these features make PostgreSQL 17 a powerful and efficient database system. By leveraging these new capabilities, you can optimize your database operations and take advantage of the latest advancements in PostgreSQL.