On 10/01/2014 07:28 PM, Thomas Munro wrote:
> Hi
>
> SQL:2003 introduced the function NEXT VALUE FOR <sequence>. Google
> tells me that at least DB2, SQL Server and a few niche databases
> understand it so far. As far as I can tell there is no standardised
> equivalent of currval and setval (but I only have access to second
> hand information about the standard, like articles and the manuals of
> other products).
>
> Here is a starter patch to add it. To avoid a shift/reduce conflict,
> I had to reclassify the keyword NEXT. I admit that I don't fully
> understand the consequences of that change! Please let me know if you
> think this could fly.
Looks correct. Of course, it's annoying to have to reserve the NEXT
keyword (as a type_func_name_keyword, not fully reserved).
One way to avoid that is to collapse NEXT VALUE FOR into a single token
in parser.c. We do that for a few other word pairs: NULLS FIRST, NULLS
LAST, WITH TIME and WITH ORDINALITY. In this case you'd need to
look-ahead three tokens, not two, but I guess that'd be doable.
- Heikki
