Re: Sub-selects taking way too long..

Поиск
Список
Период
Сортировка
От Stephan Szabo
Тема Re: Sub-selects taking way too long..
Дата
Msg-id 20020409135434.K98278-100000@megazone23.bigpanda.com
обсуждение исходный текст
Ответ на Sub-selects taking way too long..  ("Alexis Maldonado" <amaldona@ctcd.cc.tx.us>)
Список pgsql-general
On Tue, 9 Apr 2002, Alexis Maldonado wrote:

> Ok.. I know its provably something im doing dumb..
> but here it goes..
>
> I have 2 tables that are the same:
>
> "temp_table" and "table"
>
> "temp _table" has 7,761 rows and "table" is empty
>
> the columns for both tables are: ID (primary key sequence), index, column1,
> column2
>
> when i run:
>
> Insert Into table
> select index, column1, column2
> from temp_table
> where index NOT IN (select index from table)

IN is unfortunately implemented slowly (I think the FAQ answer has more
details)

You can often get better performance using exists, I think the equivalent
would be:
insert into table
select index, column1, column2 from temp_table
where NOT EXISTS (select * from table where table.index=temp_Table.index)



В списке pgsql-general по дате отправления:

Предыдущее
От: Stephan Szabo
Дата:
Сообщение: Re: table alias nor valid for delete
Следующее
От: Justin Clift
Дата:
Сообщение: More UB-Tree patent information