Simple IN vs IN values performace

[Oleksandr Voytsekhovskyy <av@xxxxxxxxx>]

Greetings,

We have queries with IN filters with long list of INT values

Sometimes, they running extremely slow, and I have found suggestion to use syntax

Field IN (VALUES(1465), (1478), ...

Instead of 

Field IN (1465, 1478, ...

On some cases it helps, but on other it makes query running 1000+ times slower

So the issue is:

- some queries much faster with simple IN

- some queries much faster with IN + VALUES

Here is explain on case when it’s extremely slow:

->  HashAggregate  (cost=5.78..9.62 rows=385 width=4)
       Group Key: ""*VALUES*"".column1" 
                   ->  Values Scan on ""*VALUES*""  (cost=0.00..4.81 rows=385 width=4)" 

What is the right way to pass long INT values list to IN filter?

I am using PostgreSQL 13.1 on Ubuntu