Re: Postmaster Crashing - Postgres 11 when JIT is enabled

Thanks for responding to my query.

I have simultaneously opened a bug with AWS too.

Issue happens with large tables (size > 5 GB) and is consistent across
multiple databases. It does not happen when JIT is disabled
or max_parallel_workers_per_gather = 0 is used in a session.

I am not running the query just starting it and then cancelling in between
- using Control + C, which causes postmaster to crash.

Here is the table definition

Column | Type | Collation | Nullable | Default |
Storage | Stats target | Description
---------------------+--------------------------+-----------+----------+---------+----------+--------------+-------------
id | text | | not null |
| extended | |
event | text | | not null |
| extended | |
unique_id | uuid | | not null |
| plain | |
surgate_id | text | | |
| extended | |
user_agent | text | | |
| extended | |
code | text | | |
| extended | |
encrypted. | text | | |
| extended | |
hash | text | | |
| extended | |
start_time | timestamp with time zone | | not null |
| plain | |
expected_expiration | timestamp with time zone | | |
| plain | |
end_time | timestamp with time zone | | |
| plain | |
level | text | | |
| extended | |
Indexes:

"sessions_pkey" PRIMARY KEY, btree (id)
"id_date" btree (unique_id, expected_expiration)
"sessions_rid" btree (unique_id)
"sessions_surrogate_id" btree (surgate_id)

Thanks & Regards,

Mukesh
On Tue, Jun 9, 2020 at 2:11 PM Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On 2020-06-09 14:00:06 -0500, Mukesh Chhatani wrote:
> > We are experiencing issues around Postmaster crashing due to cancellation
> > of a simple query
> >
> > Postgres Version - 11.6
> > Environment - AWS RDS
> > Table Size - 50 GB
>
> Unfortunately we do not have access to the exact changes RDS has done to
> postgres, so we cannot easily debug such problems.
>
>
> > Few ways I resolved the issue :
> > 1. Vacuum analyze the table and then execute the query and cancel it.
> > 2. Disable JIT
> > 3. Set max_parallel_workers_per_gather = 0
> >
> > Attached is the file containing DEBUG logs and ERROR we are experiencing
> > issues with.
>
> I am afraid that we need more information to be able to debug this
> problem. The best would be a backtrace of the crash, but for that you'd
> likely need help from RDS support.
>
> Can you post the exact table definition of the table with the problem?
> And an EXPLAIN for the problematic query?
>
>
> Are you saying that after
> > 1. Vacuum analyze the table and then execute the query and cancel it.
>
> the problem does not occur anymore for future queries?
>
> Greetings,
>
> Andres Freund
>