Query hints: You asked for it, Postgres 19 gave it to you. Now, they are just waiting to see how you use it.
For years the Postgres community was against adding support for hints. They felt if you had correctly analyzed tables, the Postgres query planner would make the right choice. And they're not wrong, for the most part. Yet many DBAs and developers will tell you of a time when a plan suddenly changed or something was saved by a hint. We can debate the good and bad elements of hints, but the cool thing is that you will soon have a choice in Postgres 19+.
So what are query hints? I came from the SQL Server world like many folks in the Postgres world and they were just there. Oracle, too. They are explicit instructions you give with SQL to change the default execution plan. Note: While industry standard refers to these as "hints," Postgres 19 uses the term "advice," so use both when searching.
This feature, expected later this fall, is coming to Postgres 19 via two new contrib modules (extensions packaged with Postgres that have to be explicitly turned on, like pg_stat_statements, everyone's favorite extension).
- pg_plan_advice - which lets you set query plan advice, like "join order" and "scan type." This also adds a new EXPLAIN option to get the plan advice for any query.
- pg_stash_advice - this lets you save plan advice strings per query id, so if you run the same query over and over (or a parameterized query), it will default to your advice instead of the planner's.
Here's a quick look at what it looks like to turn on plan advice and use it:
