Re: delete statement returning too many results - Mailing list pgsql-general

On 11/28/22 07:29, Arlo Louis O'Keeffe wrote:
> Hello everyone,
>
> I am seeing weird behaviour of a delete statement that is returning more results than I am expecting.
>
> This is the query:
>
> DELETE FROM queue
> WHERE
>     id IN (
>         SELECT id
>         FROM queue
>         ORDER BY id
>         LIMIT 1
>         FOR UPDATE
>         SKIP LOCKED
>     )
> RETURNING *;
>
> My understanding is that the limit in the sub-select should prevent this query from ever
> returning more than one result. Sadly I am seeing cases where there is more than one result.
>
> This repository has a Java setup that pretty reliably reproduces my issue:
> https://github.com/ArloL/postgres-query-error-demo
>
> I checked the docs for select and delete and couldn’t find any hint for cases
> where the behaviour of limit might be surprising.
>
> Am I missing something?

More than one row will be deleted if there in more than one record in 
"queue" for the specific value of "id" (i.e "id" is not unique).

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