Comments on: New SPARQL Parser merged

By: sfaubel

sfaubel — Sat, 15 Aug 2009 08:32:11 +0000

Hi juergbi! Nice work, really. Do you plan to support query optimization sometime in the future?

By: mvo

mvo — Fri, 14 Aug 2009 22:37:23 +0000

Awesome! Right at the time where I get some crazy ideas about extending SparQL to allow ContextKit properties and GConf/GSettings values to parameterize Tracker queries. That would be used for a “Context Cron” daemon that would be excellent at life queries and running actions whenever the result changes.

This is probably best done outside of Tracker, and we would need a SparQL parser of our own for that. We would parse the queries, plug in the property and setting values and hand the result to Tracker.

So, do you think your parser can be easily used to transform one SparQL into another?

(This old Lisp head here considers all parsing related things to be accidental complexity actually and has to cry a bit everytime things go pear shaped because some language needs to be invented or some values need to be treated abstractly, but hey, this is the real world…

(Also, hand written recursive descent parsers are the way to go for any non-toy parser, so kudos for this choice!)

By: lariamat

lariamat — Fri, 14 Aug 2009 21:30:07 +0000

Did you write the parser in vala?

By: juergbi

juergbi — Fri, 14 Aug 2009 17:29:06 +0000

@Dave: I understand that building the AST was by design and it’s a perfectly valid design in general. However, for our purposes the AST is not necessary, and we want to avoid the memory and performance overhead as Tracker will be used on embedded devices with limited resources.

We did not contact you as the AST-less parser wouldn’t fit into Rasqal and code from the existing yacc parser couldn’t have been reused, as far as I can tell from my knowledge of the Rasqal codebase. I hope I haven’t missed an opportunity for collaboration.

By: Dave Beckett

Dave Beckett — Fri, 14 Aug 2009 17:07:46 +0000

I would have been happy to talk with you about this and performance. INSERT is a non-standard part of sparql and implemented in rasqal as experimental code and likely not optional for large queries as you describe. flex+yacc does not deal with that well, and the full abstract syntax tree was by design, appropriate for standard sparql without inserts.

The rasqal API and sparql work is under active development and the query algebra is a lot more compliant than before (test cases driven). You might not need all of that for your use cases.

By: pvanhoof

pvanhoof — Fri, 14 Aug 2009 16:05:17 +0000

Whoohoo!