PostgreSQL

What's new in this version:

Introducing asynchronous I/O:
- PostgreSQL previously relied on operating system readahead mechanisms to accelerate data retrieval. However, because operating systems lack insight into database-specific access patterns, they cannot always anticipate what data will be required, leading to suboptimal performance in many workloads.
- PostgreSQL 18 introduces a new asynchronous I/O (AIO) subsystem designed to address this limitation. AIO lets PostgreSQL issue multiple I/O requests concurrently instead of waiting for each to finish in sequence. This expands existing readahead and improves overall throughput. AIO operations supported in PostgreSQL 18 include sequential scans, bitmap heap scans, and vacuum. Benchmarking has demonstrated performance gains of up to 3x in certain scenarios.
- The new io_method setting lets you toggle between the AIO methods, including worker and io_uring, or you can choose to maintain the current PostgreSQL behavior with the sync setting. There are now more parameters to consider tuning with AIO, which you can learn more about in the documentation.

Faster upgrades, better post-upgrade performance:
- A key PostgreSQL feature is the generation and storage of statistics that help PostgreSQL select the most efficient query plan. Before PostgreSQL 18, these statistics didn't carry over on a major version upgrade, which could cause significant query performance degradations on busy systems until the ANALYZE finished running. PostgreSQL 18 introduces the ability to keep planner statistics through a major version upgrade, which helps an upgraded cluster reach expected performance more quickly after the upgrade.
- Additionally, pg_upgrade, a utility that performs major version upgrades, includes several enhancements in PostgreSQL 18, such as faster upgrades when a database contains many objects like tables and sequences. This release also lets pg_upgrade process its checks in parallel based on the settings of the --jobs flag, and adds the --swap flag that swaps upgrade directories instead of copying, cloning, or linking files.

Query and general performance enhancements:
- PostgreSQL 18 further accelerates query performance with features that automatically make your workloads faster. This release introduces "skip scan" lookups on multicolumn B-tree indexes that improve execution time for queries that omit an = condition on one or more prefix index columns. It can also optimize queries that use OR conditions in a WHERE to use an index, leading to significantly faster execution. There are also numerous improvements for how PostgreSQL plans and executes table joins, from boosting the performance of hash joins to allowing merge joins to use incremental sorts. PostgreSQL 18 also supports parallel builds for GIN indexes, joining B-tree and BRIN indexes in supporting this capability.
- This release also builds on PostgreSQL support for hardware acceleration, including support for ARM NEON and SVE CPU intrinsics for the popcount function, which is used by the bit_count and other internal capabilities.

Enhancing the developer experience:
- PostgreSQL 18 introduces virtual generated columns that compute values at query time instead of storing them. This is now the default option for generated columns. Additionally, stored generated columns can now be logically replicated.
- This release adds the capability to access both the previous (OLD) and current (NEW) values in the RETURNING clause for INSERT, UPDATE, DELETE and MERGE commands. PostgreSQL 18 also adds UUIDv7 generation through the uuidv7() function, letting you generate random UUIDs that are timestamp-ordered to support better caching strategies. PostgreSQL 18 includes uuidv4() as an alias for gen_random_uuid().
- PostgreSQL 18 adds temporal constraints -- constraints over ranges -- for both PRIMARY KEY and UNIQUE constraints using the WITHOUT OVERLAPS clause, and on FOREIGN KEY constraints using the PERIOD clause
- Finally, PostgreSQL 18 makes it easier to create the schema definition of a foreign table using the definition of a local table with the CREATE FOREIGN TABLE ... LIKE command

Improved text processing:
- PostgreSQL 18 makes text processing easier and faster with several new enhancements. This release adds the PG_UNICODE_FAST collation, which provides full Unicode semantics for case transformations while helping to accelerate many comparisons. This includes the upper and lower string comparison functions and the new casefold function for case-insensitive comparisons. Additionally, PostgreSQL 18 now supports making LIKE comparisons over text that uses a nondeterministic collation, simplifying how you can perform more complex pattern matching. This release also changes full text search to use the default collation provider of a cluster instead of always using libc, which may require you to reindex all full text search and pg_trgm indexes after running pg_upgrade.
- Authentication and security features:
- PostgreSQL 18 introduces oauth authentication, which lets users authenticate using OAuth 2.0 mechanisms supported through PostgreSQL extensions. Additionally, PostgreSQL 18 includes validation for FIPS mode, and adds the ssl_tls13_ciphers parameter for configuring server-side TLS v1.3 cipher suites.
- This release deprecates md5 password authentication, which will be removed in a future release. If you require PostgreSQL password-based authentication, use SCRAM authentication. PostgreSQL 18 also supports SCRAM passthrough authentication with both postgres_fdw and dblink for authenticating to remote PostgreSQL instances. Additionally, pgcrypto now supports SHA-2 encryption for password hashing.

Replication:
- PostgreSQL 18 supports reporting logical replication write conflicts in logs and in the pg_stat_subscription_stats view. Additionally, CREATE SUBSCRIPTION now defaults to using parallel streaming for applying transactions, which can help improve performance. The pg_createsubscriber utility now has an --all flag so you can create logical replicas for all databases in an instance with a single command. PostgreSQL 18 also lets you automatically drop idle replication slots to help prevent storing too many write-ahead log files on a publisher.

Maintenance and observability:
- PostgreSQL 18 improves its vacuum strategy by proactively freezing more pages during regular vacuums, reducing overhead and helping in situations that require aggressive vacuums.
- PostgreSQL 18 adds more details to EXPLAIN, which provides information about query plan execution, and as of this release now automatically shows how many buffers (the fundamental unit of data storage) are accessed when executing EXPLAIN ANALYZE. Additionally, EXPLAIN ANALYZE now shows how many index lookups occur during an index scan, and EXPLAIN ANALYZE VERBOSE includes CPU, WAL, and average read statistics. PostgreSQL 18 includes more info in pg_stat_all_tables on time spent on vacuum and related operations, as well as per-connection statistics on I/O and WAL utilization.

Other notable changes:
- Databases initialized with PostgreSQL 18 initdb now have page checksums enabled by default. This can affect upgrades from non-checksum enabled clusters, which would require you to create a new PostgreSQL 18 cluster with the --no-data-checksums option when using pg_upgrade.
- PostgreSQL 18 also introduces a new version (3.2) of the PostgreSQL wire protocol, the first new protocol version since PostgreSQL 7.4 (2003). libpq still uses version 3.0 by default while clients (e.g., drivers, poolers, proxies) add support for the new protocol version.

Additional Features:
- Many other new features and improvements have been added to PostgreSQL 18 that may also be helpful for your use cases. Please see the release notes for a complete list of new and changed features.