[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Why not reinvent the wheel?
- From: Jonathan Robie <Jonathan.Robie@SoftwareAG-USA.com>
- To: Vasileios Papadimos <email@example.com>, Evan Lenz <firstname.lastname@example.org>
- Date: Thu, 01 Mar 2001 12:08:13 -0500
At 06:33 PM 2/26/2001 -0800, Vasileios Papadimos wrote:
>I am not sure about that (and this is true for XQuery too!)
>One way of enforcing implementation strategies is overspecifying.
>As an example, saying that joins respect the ordering of their inputs,
>pretty much forces us to exclude hash-based join algorithms.
>Do we really care about ordering in this case? For "human-readable" documents,
>certainly. For "data-oriented" documents we don't; specifying
>ordering forces us to use a, sometimes slower, nested-loops join
Would an operator that indicates that order is irrelevant satisfy your wish
here? Something like this:
FOR $a IN unordered(//author),
$e IN unordered(//editor)
WHERE $a/name = $e/name
I think this is a real issue. Let me check the issues list....yep, we've
got this covered in the issue "xquery-unordered-collections", which I
append. Does this cover what you want?
Issue 25 : Support for Unordered Collections (xquery-unordered-collections)
Originator: Algebra Editors
Does XQuery need features to add support for unordered collections? If so,
what features are required? In the current draft, "unordered" is a property
of a list. The user can create an ordered list from an unordered list by
using SORTBY. The distinct() function not only removes duplicates from a
list, it also renders the list unordered.
Do we need a function that merely removes the ordered property of a list?
How does the ordered/unordered property of a list affect the semantics of
operators applied to it?