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Thread: Re: [PATCHES] Lock

Re: [PATCHES] Lock

From
Peter Eisentraut
Date:
On 1999-12-18, Bruce Momjian mentioned:

> > * Allow LOCK TABLE tab1, tab2, tab3 so all tables locked in unison

> It took a few minutes, but I remember the use for this.  If you are
> going to hang waiting to lock tab3, you don't want to lock tab1 and tab2
> while you are waiting for tab3 lock.  The user wanted all tables to lock
> in one operation without holding locks while waiting to complete all
> locking.
> 
> Can you do the locks, and if one fails, not hang, but unlock the
> previous tables, go lock/hang on the failure, and go back and lock the
> others? Seems it would have to be some kind of lock/fail/unlock/wait
> loop.

That's what I suspected. But of course LockRelation() doesn't return
anything based on whether it succeeded, it just hangs, so it'll take a
little more work. Next year ...

-- 
Peter Eisentraut                  Sernanders väg 10:115
peter_e@gmx.net                   75262 Uppsala
http://yi.org/peter-e/            Sweden

Re: [HACKERS] Re: [PATCHES] Lock

From
Bruce Momjian
Date:
[Charset ISO-8859-1 unsupported, filtering to ASCII...]
> On 1999-12-18, Bruce Momjian mentioned:
> 
> > > * Allow LOCK TABLE tab1, tab2, tab3 so all tables locked in unison
> 
> > It took a few minutes, but I remember the use for this.  If you are
> > going to hang waiting to lock tab3, you don't want to lock tab1 and tab2
> > while you are waiting for tab3 lock.  The user wanted all tables to lock
> > in one operation without holding locks while waiting to complete all
> > locking.
> > 
> > Can you do the locks, and if one fails, not hang, but unlock the
> > previous tables, go lock/hang on the failure, and go back and lock the
> > others? Seems it would have to be some kind of lock/fail/unlock/wait
> > loop.
> 
> That's what I suspected. But of course LockRelation() doesn't return
> anything based on whether it succeeded, it just hangs, so it'll take a
> little more work. Next year ...

Yep, I figured it would be weird to get working.

--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026

Re: [HACKERS] Re: [PATCHES] Lock

From
Tom Lane
Date:
>> That's what I suspected. But of course LockRelation() doesn't return
>> anything based on whether it succeeded, it just hangs, so it'll take a
>> little more work. Next year ...

I think this would actually have to be implemented inside the lock
manager in order to make it work right.
        regards, tom lane