Re: LOCK for non-tables

On Fri, 2011-01-14 at 13:58 -0500, Tom Lane wrote:
> Robert Haas <robertmhaas@gmail.com> writes:
> > Tom - I am willing to implement this if you think it's valuable, but
> > I'd like your input on the syntax.
> > http://archives.postgresql.org/pgsql-hackers/2011-01/msg00472.php
> 
> It looks to me like the reason why there's a shift/reduce conflict is
> not so much that TABLE is optional as that we allow the syntax
> 
>     LOCK tablename NOWAIT
> 
> If that weren't possible, then a table name would have to be followed by
> EOL or IN (which is full-reserved), while an optional object type name
> could not be followed by either, so there would be no shift/reduce
> conflict.  So we broke it when we added NOWAIT, not when TABLE was made
> optional.
> 
> So it looks to me like there are at least two fixes other than the ones
> you enumerated:
> 
> 1. Make NOWAIT a reserved word.  Not good, but perhaps better than
> reserving all the different object type names.
> 
> 2. Disallow the above abbreviated syntax; allow NOWAIT only after an
> explicit IN ... MODE phrase.  This would probably break a couple of
> applications, but I bet a lot fewer than changing the longer-established
> parts of the command syntax would break.
> 
> I think #2 might be the best choice here.

There's a similar issue on my new syntax for skipping the validation
check on FKs. I'd appreciate it if you could propose a solution there
also. I'm not sure whether I solved it, or am adding issues for the
future.

-- Simon Riggs           http://www.2ndQuadrant.com/books/PostgreSQL Development, 24x7 Support, Training and Services