Re: [xml] [Patch] Optimizing '//' in XPath expressions

[Liam R E Quin <liam holoweb net>]

On Fri, 2012-08-24 at 12:21 +0800, Daniel Veillard wrote:
[...]
> I suspect it's just the top of the iceberg, there is a number of other
> post-compilation optimization which can certainly be made, but with
> less drastic improvements.

Mike Kay has spoken at I think XML Prague and/or Balisage about the
optimizations in Saxon; from my imperfect memory :) they include
building an element index during parsing, expression rewriting, and
using a bytecode interpreter.

There have been papers on XPath optimization in the context of XQuery,
some of which may also apply (e.g. at VLDB).

I think a lot of stylesheet writers have learned to avoid //x even in
implementations where it's basically O(1) these days. But it's still
worth speeding up :-)

Liam

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Co-author: 5th edition of "Beginning XML" - Wrox, July 2012

-- 
Liam Quin - XML Activity Lead, W3C, http://www.w3.org/People/Quin/
Pictures from old books: http://fromoldbooks.org/
Ankh: irc.sorcery.net irc.gnome.org freenode/#xml