Re: Locking concurrency: select for update vs update - Mailing list pgsql-performance

From Streamsoft - Mirek Szajowski
Subject Re: Locking concurrency: select for update vs update
Date
Msg-id 2af91a21-bdaf-f245-0b88-2046064ccce6@streamsoft.pl
Whole thread Raw
In response to Re: Locking concurrency: select for update vs update  (Tom Lane <tgl@sss.pgh.pa.us>)
List 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


pgsql-performance by date:

Previous
From: Tom Lane
Date:
Subject: Re: Locking concurrency: select for update vs update
Next
From: Rafał Gutkowski
Date:
Subject: Combination of partial and full indexes