Re: Long running query causing XID limit breach

Greetings,

Running `VACUUM table_name;` on a partitioned table will vacuum each
partition individually, not the whole table as a single unit.

Yes, running `VACUUM table_name;` frequently on tables or partitions with
heavy DML is recommended.

Regular `VACUUM` does not lock the table for reads or writes, so it won't
disrupt ongoing 24/7 data operations.

"optimize autovacuum"
Yes. Adjust following parameters as per your system/environment requirement
autovacuum_max_workers,
autovacuum_freeze_max_age ,
autovacuum_vacuum_cost_delay

Following need to be first tested thoroughly in a test environment.
Recommended Alert Threshold
Alert at 50% Usage: Set the alert threshold at 1 billion used XIDs. This
provides a significant buffer, giving you ample time to take corrective
action before reaching the critical limit.

Calculation Rationale
Daily XID Usage: Approximately 4 billion rows per day implies high XID
consumption.
Buffer Time: At 1 billion XIDs, you would still have 1 billion XIDs
remaining, giving you roughly 12 hours to address the issue if your system
consumes 200 million XIDs per hour.

*Salahuddin (살라후딘**)*

On Thu, 23 May 2024 at 09:48, sud <suds1434(at)gmail(dot)com> wrote:

> On Thu, May 23, 2024 at 9:00 AM Muhammad Salahuddin Manzoor <
> salahuddin(dot)m(at)bitnine(dot)net> wrote:
>
>> Greetings,
>>
>> In high-transaction environments like yours, it may be necessary to
>> supplement this with manual vacuuming.
>>
>> Few Recommendations
>>
>> Monitor Long-Running Queries try to optimize.
>> Optimize Autovacuum.
>> Partitioning.
>> Adopt Vacuum Strategy after peak hours.
>>
>> We have these big tables already partitioned. So does "vacuum table_name"
> will endup scanning whole table or just the latest/live partition which is
> getting loaded currently? and do you mean to say running command "vacuum
> table_name;" frequently on selective tables that are experiencing heavy DML
> ? Hope this won't lock the table anyway because the data will be
> written/read from these tables 24/7.
>
> When you say, "optimize autovacuum" does it mean to set a higher value of "autovacuum_max_workers"
> and "autovacuum_freeze_max_age"?
>
> Considering we have ~4 billion rows inserted daily into the table and
> there is limit of ~2billion to the "Maximumusedtxnids", what threshold
> should we set for the alerting and to have enough time at hand to fix this
> issue?
>
>