Re: this is in plain text (row level locks)

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> I suppose we could allow one backend to mark the page with a shared lock
> for primary key purposes while others read it.  Does that buy us
> anything?

That doesn't work, unless you insist that the first backend can't exit
its transaction until all the other ones are done.  Which introduces its
own possibilities for deadlock --- but even worse, how does the first
backend *know* that the other ones are done?  You're right back where
you started: it has to be possible to tell which backends have
share-locked a particular row.
        regards, tom lane