Sorry to bother you folks but...
I wrote the following to message to pgsql-interfaces. I have received one
work around of putting an extra locked field on the table and setting and
unsetting that but that would cause other problems. I have thought of
creating a locking daemon of my own for the application to request locks
from but that would be very hard to figure out as I've never tried ipc. I
have read through lock.c again and I think that user locks may be what I
want, as there is only one table that needs to be protected this way in my
application. I just don't know how to proceed.
Thanks
Trevor
>I am using Postgres 6.5 on Linux through the libpq interface
>
>I have a situation where an existing record can be opened by one user,
>updated or rolled back. While the first user has the record I need to make
>sure no other user can open it. I use
>
>SELECT .... FOR UPDATE
>
> This works but the second process blocks (looking to the user like a hung
> program), until the first process releases the record. Since updating a
> record can take some time the blocking could be there for some time.
>
> I would like the second SELECT .... FOR UPDATE to fail with an error I can
> catch telling me of a conflict (and hopefully which process has the lock),
> allowing me to backout gracefully with a consolatory message to the user.
I
> would like normal SELECTs (without FOR UPDATE) to work an normal.
>
> I think that this is an option in pg_options but I'm not sure. I have
looked
> in the source (lock.c and lmgr.c) to try and figure out what to do. I
found
> something called "user locks" which looks promising but I'm still not
sure.
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