On 17/11/11 17:11, Juergen Umbrich wrote:
Hi all,
i am wondering if there is any code examples or documentation of how
to learn about query optimization in ARQ? Especially if i want to
assign weights to triple patterns and restrict myself to BGP
queries. In addition, is there any possibility to get a list of all
possible query plans?
Juergen,
Paolo pointed to:
http://jena.staging.apache.org/jena/documentation/query/arq-query-eval.html
Optimization happens in two places: Optimize (which is the high-level
algebra->algebra rewrites) and at the point a BGP is executed.
TDB does the low-level reordering within a BGP (the engine for this is
in ARQ ...sparql.engine.optimize.reorder. ReorderLib has the collection of
http://jena.staging.apache.org/jena/documentation/tdb/optimizer.html
TDB does not work by enumerating plans and searching amongst them. It's
more fixed than that.
There are lots of ways to improve optimization.
Also "explain" for running with details of what it's doing.
http://openjena.org/wiki/ARQ/Logging
(seem to be still on the old wiki)
Andy
