Re: Lock

Added to TODO.detail lock file.

On Sat, 18 Dec 1999, Bruce Momjian wrote:

[Charset ISO-8859-1 unsupported, filtering to ASCII...]

I was looking at this

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

but I'm not sure if my solution is really what was wanted, because it
doesn't actually guarantee an all-or-nothing lock, it just locks each
table in order. Thus it's more like a syntax simplification and reduces
overhead.

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.

Does this make sense? It did to me.

Guys, have a look at:

http://www.freebsd.org/~terry/iml.txt
http://jazz.external.hp.com/training/sqltables/c5s17.html

It's a way to do locking with deadlock detection, and without loosing
your place in line for locks, very nifty imo.

-Alfred

************

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