Re: Some surprising precedence behavior in PG's grammar

I wrote:
> Andrew Dunstan <andrew@dunslane.net> writes:
>> If we do need a precedence setting for NULL_P, then I think it should 
>> probably be on its own and not sharing one with IS.

> Yeah, I was thinking that too.  If we put %prec on the IS [NOT] NULL
> productions then there is no need for NULL_P to have exactly its current
> precedence; anything above POSTFIXOP would preserve the current behavior
> in the DEFAULT ... NULL case.  (And if we decided we wanted to flip that
> behavior, anything below POSTFIXOP would do that.)

On reflection I decided that the best quick-fix is to put NULL into the
list of keywords that are already precedence-grouped with IDENT.  That
at least makes sure that it has precedence behavior equivalent to any
plain old non-keyword.  If you can find a better fix, maybe we could
apply it to the other cases mentioned there as well.

> BTW, I wonder why NOTNULL and ISNULL have their own precedence levels,
> rather than being made to act exactly like IS [NOT] NULL ...

Is anybody up for changing that, or should we leave well enough alone?
        regards, tom lane