On 05/10/13 08:45, Andrea Dessi wrote:
Hi,
I've got jena-text working to do Lucene indexing, and I'd like to know the
technical differences between text:query and filter regex.
Thanks for any help,
Andrea
Hi Andrea,
I'm not sure what aspect you mean but
text:query is a property function - it looks like part of the basic
graph pattern and it can generate answers, binding variables. A filter
can not do that - all it can do is take a stream of possibilities and
accept or reject them. Optimizers may do magic things in certain cases
but, in general, it is a case of generating all possibilities which may
may be a huge amount of work, and reducing it to a few results. That's
why FILTER regex can be very expensive.
The lucene (or Solr) index used by text:query only generate the possible
matches because, being an index, the Lucene engine looks up the query
string (or some part of) to find a moderate number of possibilites.
There is no "get everything and reduce" effect.
Andy
