Re: Shared row locking

Heikki Linnakangas <hlinnaka@iki.fi> writes:
> On Sun, 19 Dec 2004, Alvaro Herrera wrote:
>> This is not useful at all, because the objective of this exercise is to
>> downgrade locks, from exclusive row locking (SELECT ... FOR UPDATE) to
>> shared row locking.

> Actually it might help in some scenarios. Remember, we're not talking 
> about upgrading shared locks to exclusive locks. We're only talking about 
> locking more rows than necessary (all rows).

Nonetheless, it would mean that locks would be taken depending on
implementation-dependent, not-visible-to-the-user considerations.
Shared locks can still cause deadlocks, and so you would have an
unreliable application, which would only be unreliable under load.

As I said in connection with the other proposal, weird user-visible
semantics should be the last resort not the first.
        regards, tom lane