Re: Locking concurrency: select for update vs update

Поиск
Список
Период
Сортировка
От Streamsoft - Mirek Szajowski
Тема Re: Locking concurrency: select for update vs update
Дата
Msg-id 2af91a21-bdaf-f245-0b88-2046064ccce6@streamsoft.pl
обсуждение исходный текст
Ответ на Re: Locking concurrency: select for update vs update  (Tom Lane <tgl@sss.pgh.pa.us>)
Список pgsql-performance

Thanks

after your description I found select name from phone_number_type  WHERE id_phone_number_type=4 for NO KEY update (Postgresql 9.3 )

W dniu 2016-06-07 o 15:24, Tom Lane pisze:
Streamsoft - Mirek Szajowski <m.szajowski@streamsoft.pl> writes:
Why I can't execute 'select for update' but I can update?
In recent PG versions, the lock held due to having inserted an FK
dependent row effectively only locks the key fields of the parent row.
UPDATE can tell whether you're trying to change the row's key fields,
and it will proceed if you aren't.  SELECT FOR UPDATE has to lock the
whole row (since it must assume you might be intending to change any
fields of the row); so it blocks until the FK lock goes away.
		regards, tom lane


В списке pgsql-performance по дате отправления:

Предыдущее
От: Tom Lane
Дата:
Сообщение: Re: Locking concurrency: select for update vs update
Следующее
От: Rafał Gutkowski
Дата:
Сообщение: Combination of partial and full indexes