Re: Using ctid column changes plan drastically

От: Tom Lane
Тема: Re: Using ctid column changes plan drastically
Дата: ,
Msg-id: 21308.1343139781@sss.pgh.pa.us
(см: обсуждение, исходный текст)
Ответ на: Using ctid column changes plan drastically  (Thomas Kellerer)
Ответы: Re: Using ctid column changes plan drastically  (Thomas Kellerer)
Список: pgsql-performance

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Using ctid column changes plan drastically  (Thomas Kellerer, )
 Re: Using ctid column changes plan drastically  (Tom Lane, )
  Re: Using ctid column changes plan drastically  (Thomas Kellerer, )
   Re: Using ctid column changes plan drastically  (Tom Lane, )
    Re: Using ctid column changes plan drastically  (Thomas Kellerer, )
     Re: Using ctid column changes plan drastically  (Tom Lane, )
      Re: Using ctid column changes plan drastically  (Thomas Kellerer, )
       Re: Using ctid column changes plan drastically  ("Kevin Grittner", )

Thomas Kellerer <> 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


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