Re: Common Table Expressions (WITH RECURSIVE) patch

On 2 Oct 2008, at 05:44 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

> "Hitoshi Harada" <umi.tanuki@gmail.com> writes:
>
>> Hmm, I've looked over the patch. Logically window functions can  
>> access
>> arbitrary rows that have been stored in a frame. Thus I had thought
>> tuplestore should hold all the positions and allow arbitrary random
>> access indicated by integer. Maybe those functionalities can be
>> abstracted by the window function API itself. For this matter it  
>> seems
>> that you'd better to look at my future patch.
>
> Well, the problem with defining it as "arbitrary" random access is  
> that
> there's no way for the tuplestore to throw away old data.

And that there's no way to make it work if the tuplestore has spilled  
to disk.