Thread

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

David G. Johnston <david.g.johnston@gmail.com> — 2025-11-04T13:26:01Z

On Tuesday, November 4, 2025, PG Bug reporting form <noreply@postgresql.org>
wrote:

> The following bug has been logged on the website:
>
> Bug reference:      19103
> Logged by:          Jinhui Lai
> Email address:      jinhui.lai@qq.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.