Re: Using ctid column changes plan drastically - Mailing list pgsql-performance

Thomas Kellerer <spam_eater@gmx.net> writes:
> DELETE FROM dupes
> WHERE id NOT IN (SELECT min(b.id)
>                   FROM   dupes b
>                   GROUP BY first_name, last_Name
>                   HAVING count(*) > 1);

Doesn't that kill the non-duplicates too?

> Why does the usage of the CTID column change the plan so drastically?

IIRC, type tid doesn't have any hash support.

            regards, tom lane