[Xapian-discuss] Can xapian do geo search/calculations?

[Richard Boulton]

Francis Irving wrote:
> Out of interest, can you write new value range processor and/or match
> decider subclasses in a binding language?
 >
> e.g. Phython or Ruby

Yes, you should be able to.  Not all the wrapper languages currently 
support language callbacks, but those two do.  (The language needs to 
have support in SWIG for "directors", but we do the appropriate things 
in the xapian SWIG header files.)

The language specific documentation has some details about doing this.

ValueRangeProcessors and MatchDeciders can definitely be subclassed in 
Python.  MatchDeciders can definitely be subclassed in Ruby.  The 
documentation and tests for ruby don't mention ValueRangeProcessor, so 
it's possible that doesn't currently work (it needed some special 
handling to implement it in Python, because the C++ API involves a 
string being passed by reference, or something like that, which Python 
doesn't have an equivalent to).

There's a bit of an overhead to calling back to these languages (quite a 
bit, actually), but in my experience it's not as bad as you might at 
first expect calling back to Python for every document in the result set 
to be.

-- 
Richard