Re: BUG #19103: Canceled INSERT statement can still influence the performance of subsequent SELECT statement

On Tuesday, November 4, 2025, PG Bug reporting form <noreply(at)postgresql(dot)org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference: 19103
> Logged by: Jinhui Lai
> Email address: jinhui(dot)lai(at)qq(dot)com
> PostgreSQL version: 18.0
> Operating system: ubuntu 22.04
> Description:
>
> Dear PG developers:
>
> Thanks for reading my report. Here, I find a performance issue. I have
> found a performance issue where a canceled INSERT statement appears to
> negatively impact the performance of subsequent SELECT queries.

This doesn’t feel like a bug. Processing deleted rows is expensive and
some of that work happens during selects if/when those dead rows are
encountered.

> This performance degradation could affect systems where large batch
> operations are frequently started and canceled, potentially impacting
> overall database responsiveness.
>

Temporary tables are nice for this kind of flow. Don’t touch production
tables until you know what you are going to insert is going to stick.

David J.