Re: [HACKERS] MVCC works in serialized mode!

Bruce Momjian wrote:
>
> > 6. I'm not happy with current deadlock detection code!
> > It seems that backend does DeadLockCheck each time
> > when timer expired - shouldn't this be done _once_,
> > before backend is going to sleep ?!
>
> Not sure. Now that I think of it, it makes sense that if I go to sleep,
> a deadlock is not sudenly going to appear while I am asleep. If a new
> process causes a deadlock, the new process that causes it will see it.
>
> I did not check when I went to sleep because I thought it may be too
> cpu-intensive to do checking on every sleep, but now that I remember it,
> it may be very trivial in cpu time to do the check on every sleep.
>
> I recommend changing it to do it just before every sleep. Let me know
> if you want me to make the change.

May be we could just reduce first sleep time (60 sec is too long),
do DeadLockCheck _only once_, after first SIGALARM, and after that
just sleep forever ?
Why do DeadLockCheck many times ?

Let's think more...

And please consider when lock conflict occures:

1. One process tries update row being updated by other.
2. When reading/writing hashes (I hope to change btrees to
use new buffer context lock code, as heap access methods
do, - this is short term locking without deadlocks and so -
without using lockmanager).

Vadim