blog: what’s new in Postgres 18 developer

Author: tianzhou

content/blog/what-is-new-in-postgres-18-for-developer.md

@@ -0,0 +1,181 @@
+---
+title: "What's New in PostgreSQL 18 - a Developer's Perspective"
+author: Tianzhou
+updated_at: 2025/09/26 12:00
+feature_image: /content/blog/what-is-new-in-postgres-18-for-developer/cover.webp
+tags: Industry
+featured: true
+description: "Overview of PostgreSQL 18 features from a developer's perspective"
+---
+
+PostgreSQL 18 was officially released on [September 25, 2025](https://www.postgresql.org/about/news/postgresql-18-released-3142/). No doubt the most consequential change is the new Asynchronous I/O subsystem. However, this post focuses on the features that will impact developers in their day-to-day work, starting with native UUID v7 support.
+
+## Native UUID v7 Support
+
+- Commit: [78c5e141e](https://postgr.es/c/78c5e141e)
+- Docs: https://www.postgresql.org/docs/18/datatype-uuid.html
+
+PostgreSQL 18 introduces the `uuidv7()` function for generating UUID version 7 values. This native support almost closes the long-standing debate about whether to use `SERIAL/IDENTITY` types or UUIDs as primary keys. UUIDv7 combines the best of both worlds: the global uniqueness of UUIDs with the sequential nature that makes serial keys perform well.
+
+```sql
+-- Generate a UUIDv7
+SELECT uuidv7();
+
+-- Create a table using UUIDv7 as primary key
+CREATE TABLE orders (
+    id UUID PRIMARY KEY DEFAULT uuidv7(),
+    customer_id INT,
+    total DECIMAL(10,2),
+    created_at TIMESTAMP DEFAULT NOW()
+);
+```
+
+Previously, while PostgreSQL extensions could generate UUIDv7, the most widely used `uuid-ossp` extension doesn't implement v7. Lesser-known extensions that do support v7 aren't typically packaged with PostgreSQL distributions, especially on cloud providers. This meant developers wanting UUIDv7 had to implement generation logic in their applications. Native support removes this friction entirely.
+
+## VIRTUAL Generated Columns
+
+- Commit: [83ea6c540](https://postgr.es/c/83ea6c540)
+- Docs: https://www.postgresql.org/docs/18/sql-createtable.html#SQL-CREATETABLE-PARMS-GENERATED-STORED
+
+Generated columns were first introduced in PostgreSQL 12, but only with the `STORED` option, which means the generated column is stored on write and occupies disk space. Adding a `STORED` generated column will rewrite the entire table.
+
+PostgreSQL 18 introduces the `VIRTUAL` option and makes it the default behavior for generated columns. These columns compute their values when read rather than when written. This is a more common approach, and making it the default aligns PostgreSQL with other major databases.
+
+```sql
+-- Create table with virtual generated column
+CREATE TABLE employees (
+    id SERIAL PRIMARY KEY,
+    first_name TEXT NOT NULL,
+    last_name TEXT NOT NULL,
+    salary DECIMAL(10,2),
+    -- You can also skip VIRTUAL since it's the default option
+    annual_salary DECIMAL(12,2) GENERATED ALWAYS AS (salary * 12) VIRTUAL
+);
+
+-- Insert data (generated columns are computed automatically)
+INSERT INTO employees (first_name, last_name, salary) VALUES
+    ('John', 'Doe', 5000.00),
+    ('Jane', 'Smith', 6500.00);
+
+SELECT first_name, last_name, salary, annual_salary
+FROM employees;
+```
+
+Virtual column advantages:
+
+- **Space Saving**: For derived data that doesn't need physical storage, virtual columns eliminate redundant disk usage.
+
+- **Dynamic Computation**: Some computations benefit from being executed at query time, especially when they depend on current system state.
+
+On the other hand, `STORED` generated columns remain valuable for heavy computations that rarely change, where the performance cost of repeated calculation outweighs storage concerns.
+
+However, there are certain limitations as mentioned in the commit. The most noticeable one is that you cannot create indexes on `VIRTUAL` generated columns.
+
+BTW, PostgreSQL 18 also adds support for generated columns in logical replication ([commit](https://postgr.es/c/745217a05), [docs](https://www.postgresql.org/docs/18/logical-replication-gencols.html)). This feature is only available to `STORED` generated columns as well.
+
+## OLD and NEW Values in RETURNING
+
+- Commit: [80feb727c](https://postgr.es/c/80feb727c)
+- Docs: https://www.postgresql.org/docs/current/dml-returning.html
+
+PostgreSQL 18 enhances the `RETURNING` clause to access both old and new row values in DML operations. This eliminates the need for separate queries to capture before/after values in audit logs.
+
+**UPDATE Operations**
+
+```sql
+-- Update prices and see both old and new values
+UPDATE products
+SET price = price * 1.10
+WHERE price <= 99.99
+RETURNING
+    name,
+    old.price AS old_price,
+    new.price AS new_price,
+    new.price - old.price AS price_change;
+```
+
+**INSERT with ON CONFLICT**
+
+```sql
+-- Upsert with change tracking
+INSERT INTO products (name, price) VALUES ('Widget', 25.00)
+ON CONFLICT (name) DO UPDATE SET price = EXCLUDED.price
+RETURNING
+    name,
+    old.price AS previous_price,
+    new.price AS current_price,
+    (old.price IS NULL) AS is_new_record;
+```
+
+**DELETE Operations**
+
+```sql
+-- Track what was deleted
+DELETE FROM products
+WHERE price < 10.00
+RETURNING
+    old.name AS deleted_product,
+    old.price AS deleted_price;
+```
+
+## EXPLAIN ANALYZE with BUFFERS by Default
+
+- Commit: [c2a4078eb](https://postgr.es/c/c2a4078eb)
+- Docs: https://www.postgresql.org/docs/current/sql-explain.html
+
+PostgreSQL 18 improves the `EXPLAIN` command to provide more detailed query execution information automatically.
+
+`EXPLAIN ANALYZE` now includes buffer usage information by default, eliminating the need for the `BUFFERS` option. This default behavior helps developers spot I/O performance issues that would otherwise be overlooked:
+
+```sql
+postgres=# EXPLAIN ANALYZE SELECT * FROM users WHERE age > 25;
+
+-- PostgreSQL 18: BUFFERS included automatically
+ Seq Scan on users  (cost=0.00..18.75 rows=125 width=64) (actual time=0.029..0.087 rows=178 loops=1)
+   Filter: (age > 25)
+   Rows Removed by Filter: 89
+   Buffers: shared hit=12
+ Planning:
+   Buffers: shared hit=156 read=3
+   I/O Timings: shared read=0.024
+ Planning Time: 0.512 ms
+ Execution Time: 0.734 ms
+```
+
+## pg_get_acl() for Permission Inspection
+
+- Commit: [4564f1ceb](https://postgr.es/c/4564f1ceb)
+- Docs: https://www.postgresql.org/docs/18/functions-info.html#FUNCTIONS-INFO-OBJECT-TABLE
+
+PostgreSQL 18 introduces the `pg_get_acl()` function for programmatically retrieving Access Control Lists (ACLs) for database objects. If you've ever spent time debugging the infamous `ERROR 42501: permission denied` messages, you'll appreciate having a unified way to inspect object privileges.
+
+Previously, troubleshooting permissions required querying different system catalogs (`pg_class`, `pg_proc`, `pg_namespace`, `pg_attribute`) depending on the object type, each with their own ACL format.
+
+The `pg_get_acl()` function provides a unified interface for retrieving Access Control Lists from any database object, eliminating the need to remember which catalog to query for different object types.
+
+```sql
+postgres=# SELECT
+    (pg_identify_object(s.classid,s.objid,s.objsubid)).*,
+    pg_catalog.pg_get_acl(s.classid,s.objid,s.objsubid) AS acl
+FROM pg_catalog.pg_shdepend AS s
+JOIN pg_catalog.pg_database AS d
+    ON d.datname = current_database() AND
+       d.oid = s.dbid
+JOIN pg_catalog.pg_authid AS a
+    ON a.oid = s.refobjid AND
+       s.refclassid = 'pg_authid'::regclass
+WHERE s.deptype = 'a';
+-[ RECORD 1 ]-----------------------------------------
+type     | table
+schema   | public
+name     | testtab
+identity | public.testtab
+acl      | {postgres=arwdDxtm/postgres,foo=r/postgres}
+```
+
+While not as headline-grabbing as the new Asynchronous I/O subsystem, these quality-of-life improvements make day-to-day development easier—and clearer interfaces like `pg_get_acl()` benefit not only human developers, but AI agents as well.
+
+## Further Readings
+
+- [Postgres 18 full release notes](https://www.postgresql.org/docs/18/release-18.html)
+- [DBA's perspective about Postgres 18](/blog/what-is-new-in-postgres-18)

content/blog/what-is-new-in-postgres-18.md

@@ -5,7 +5,7 @@ updated_at: 2025/05/23 12:00
 feature_image: /content/blog/what-is-new-in-postgres-18/cover.webp
 tags: Industry
 featured: true
-description: 'Overview of PostgreSQL 18 features with spicy comments'
+description: "Overview of PostgreSQL 18 features with spicy comments from a DBA's perspective"
 ---
 
 <HintBlock type="info">
@@ -25,9 +25,7 @@ will constantly update this post to include the latest Postgres 18.x releases.
 - **PostgreSQL 18 Beta 2**: July 17, 2025
 - **PostgreSQL 18 Beta 3**: August 14, 2025
 - **PostgreSQL 18 RC 1**: September 4, 2025
-- **PostgreSQL 18 Official Release!**: September 25, 2025
-
-PostgreSQL just announced [18 beta 1](https://www.postgresql.org/about/news/postgresql-18-beta-1-released-3070/). While some features may still be dropped, it's worth taking a look.
+- **PostgreSQL 18 Official Release!**: September 25, 2025.
 
 ## Asynchronous I/O
 
@@ -98,3 +96,8 @@ The PostgreSQL 18 Beta 1 announcement highlights a significant improvement: the
 Of course, with any major version, there are compatibility changes to be aware of. The release notes for version 18 list several, including changes to time zone abbreviation handling, the deprecation of MD5 password authentication (finally!), changes to how `VACUUM` and `ANALYZE` handle inheritance, and modifications to `COPY FROM` behavior regarding end-of-file markers. It's crucial to review these incompatibilities thoroughly before planning an upgrade.
 
 **DBA Note:** Anything to reduce that terrifying maintenance window during upgrade is welcome. But the list of "incompatibilities" is still there, waiting to trip up the unwary. Anyway, DBAs will still need to read the fine print, test exhaustively in staging, and have a solid rollback plan. Upgrades are still where DBAs earn their hazard pay.
+
+## Further Readings
+
+- [Postgres 18 full release notes](https://www.postgresql.org/docs/18/release-18.html)
+- [Developer's perspective about Postgres 18](/blog/what-is-new-in-postgres-18-for-developer)