Re: add more frame types in window functions (ROWS)

2009/11/15 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk> writes:
>> (A question here: the spec allows (by my reading) the use of
>> parameters in the window frame clause, i.e. BETWEEN $1 PRECEDING AND
>> $2 FOLLOWING.  Wouldn't it therefore make more sense to treat the
>> values as Exprs, albeit very limited ones, and eval them at startup
>> rather than assuming we know the node type and digging down into it
>> all over the place?)
>
> Seems like you might as well allow any expression not containing
> local Vars.  Compare the handling of LIMIT.

Hmm, I've read it wrong, was assuming a constant for <unsigned value
specification> which actually includes any expression. But it's a
fixed value during execution, right? Otherwise, we cannot predicate
frame boundary.

Regards,

--
Hitoshi Harada