Archive for August, 2009

New SPARQL Parser merged

Friday, August 14th, 2009

Up to now, Tracker has used Rasqal to parse SPARQL queries received from applications. We imported a copy of Rasqal into Tracker’s source tree as we use some SPARQL extensions that are not yet fully implemented in Rasqal upstream. For the last couple of weeks I’ve been writing a new SPARQL parser, a hand-written recursive descent parser.

The motivation was to speed up (large) queries and to fix a few corner cases with OPTIONAL graph patterns that Rasqal gets wrong. Rasqal does not perform very well for large queries as it always builds a full abstract syntax tree of the query, even if it’s a very simple but long INSERT statement. The hand-written parser processes queries on the fly, trying to keep only as much state around as necessary.

The new parser has now been merged into master and should improve our SPARQL support in both speed and conformance. We’ve tested it with test cases from DAWG and it appears to work at least as well as the old parser, but I’m sure we’ve missed some bugs, so let us know if you find any issues with SPARQL in Tracker master.