RE: [HACKERS] Lock freeze ? in MVCC

> -----Original Message-----
> From: root@sunpine.krs.ru [mailto:root@sunpine.krs.ru]On Behalf Of Vadim
> Mikheev
> Sent: Tuesday, April 27, 1999 7:49 PM
> To: Hiroshi Inoue
> Cc: Bruce Momjian; pgsql-hackers@postgreSQL.org
> Subject: Re: [HACKERS] Lock freeze ? in MVCC
>
>
> Hiroshi Inoue wrote:
> >
> > Now I'm suspicious about the following code in LockResolveConflicts().
> >
> >          /*
> >          * We can control runtime this option. Default is
> lockReadPriority=0
> >          */
> >         if (!lockReadPriority)
> >         {
> >                 /* ------------------------
> >                  * If someone with a greater priority is waiting for the
> > lock,
> >                  * do not continue and share the lock, even if
> we can.  bjm
> >                  * ------------------------
>
> You're right Hiroshi - this must be changed:
>
> if we already have some lock with priority X and new requested
> lock has priority Y, Y <= X, then lock must be granted.
>
> Also, I would get rid of lockReadPriority stuff...
>

I found a problem to get rid of lockReadPriority stuff completely.
If there's a table which is insert/update/deleted very frequenly by
several processes,processes which request the high priority lock
(such as vacuum) could hardly acquire the lock for the table.

How about the following patch ?

Thanks.

Hiroshi Inoue
Inoue@tpf.co.jp

*** storage/lmgr/lock.c.orig    Wed Apr 28 10:44:52 1999
--- storage/lmgr/lock.c    Wed Apr 28 12:00:14 1999
***************
*** 815,821 ****     /*      * We can control runtime this option. Default is lockReadPriority=0      */
!     if (!lockReadPriority)     {         /* ------------------------          * If someone with a greater priority is
waitingfor the lock,
 
--- 815,821 ----     /*      * We can control runtime this option. Default is lockReadPriority=0      */
!     if ((!result->nHolding) && (!lockReadPriority))     {         /* ------------------------          * If someone
witha greater priority is waiting for the lock,