Re: Postgres 15 SELECT query doesn't use index under RLS

[Alexander Okulovich <aokulovich@xxxxxxxxxxxxx>]

Hi Tom,

I've attempted to reproduce this on my PC in Docker from the stage database dump, but no luck. The first query execution on Postgres 15 behaves like on the real stage, but subsequent ones use the index. Also, they execute much faster. Looks like the hardware and(or) the data structure on disk matters.

Here is the Docker Compose sample config:

version: '2.4'

services:

database-15:
  image: postgres:15.4
  ports:
    - "7300:5432"
  environment:
    POSTGRES_DB: stage_db
    POSTGRES_USER: stage
    POSTGRES_PASSWORD: stage
  volumes:
    - "./init.sql:/docker-entrypoint-initdb.d/init.sql"
    - "./pgdb/aws-15:/var/lib/postgresql/data"
  mem_limit: 512M
  cpus: 2
  blkio_config:
    device_read_bps:
      - path: /dev/nvme0n1
        rate: '10mb'
    device_read_iops:
        - path: /dev/nvme0n1
          rate: 2000
    device_write_bps:
        - path: /dev/nvme0n1
          rate: '10mb'
    device_write_iops:
        - path: /dev/nvme0n1
          rate: 2000

      I performed tests only with CPU and memory limits. If I try to
      limit the disk(blkio_config), my system hangs on container startup
      after a while.
      Could you please share your thoughts on how to create such a
      self-contained test case.

Kind regards,

Alexander

On 18.10.2023 22:35, Tom Lane wrote:

> If
>       you could provide a self-contained test case that performs 10x
>       worse
>       under v15 than v12, we'd surely take a look at it. But with the
>       information you've given so far, little is possible beyond
>       speculation.
>