Thread: Re: [HACKERS] [GENERAL] Bug with sequence

Re: [HACKERS] [GENERAL] Bug with sequence

From
Rod Taylor
Date:
On Thu, 2002-11-21 at 15:09, scott.marlowe wrote:
> On 21 Nov 2002, Rod Taylor wrote:
> 
> > On Thu, 2002-11-21 at 14:11, Bruce Momjian wrote:
> > > Of course, those would be SQL purists who _don't_ understand
> > > concurrency issues.  ;-)
> > 
> > Or they're the kind that locks the entire table for any given insert.
> 
> Isn't that what Bruce just said?  ;^)

I suppose so.  I took what Bruce said to be that multiple users could
get the same ID.

I keep having developers want to make their own table for a sequence,
then use id = id + 1 -- so they hold a lock on it for the duration of
the transaction.

-- 
Rod Taylor <rbt@rbt.ca>



Re: [HACKERS] [GENERAL] Bug with sequence

From
"scott.marlowe"
Date:
On 21 Nov 2002, Rod Taylor wrote:

> On Thu, 2002-11-21 at 15:09, scott.marlowe wrote:
> > On 21 Nov 2002, Rod Taylor wrote:
> > 
> > > On Thu, 2002-11-21 at 14:11, Bruce Momjian wrote:
> > > > Of course, those would be SQL purists who _don't_ understand
> > > > concurrency issues.  ;-)
> > > 
> > > Or they're the kind that locks the entire table for any given insert.
> > 
> > Isn't that what Bruce just said?  ;^)
> 
> I suppose so.  I took what Bruce said to be that multiple users could
> get the same ID.
> 
> I keep having developers want to make their own table for a sequence,
> then use id = id + 1 -- so they hold a lock on it for the duration of
> the transaction.

I was just funnin' with ya, but the point behind it was that either way 
(with or without a lock) that using something other than a sequence is  
probably a bad idea.  Either way, under parallel load, you have data 
consistency issues, or you have poor performance issues.