Xapian discuss - Nov 2006 - Searching for document-groups

Hi everybody,

my name is Christoph Hack and I am new at xapian, but I am very
impressed. I want to write a xapian based search engine for a
bulletin board. I indexed each post as a document and I can 
actually search for single posts including a specified term - that
works fine.

And now I am wondering how i can reduce the search results to
entire threads and display posts with the same root-post just once.
Of course I could sort and filter the posts after searching manually,
but I am looking for a faster (xapian based) solution :)

If there are any questions left, please feel free to ask. Thanks in
advance.

Regards
Christoph Hack

On Tue, Nov 07, 2006 at 07:59:58PM +0100, Christoph Hack
wrote:
> And now I am wondering how i can reduce the search results to
> entire threads and display posts with the same root-post just once.
If you add a value to each document (using Xapian::Document::add_value())
containing some sort of unique id for the root-post of the thread that
the current article is in, you can collapse matches with the same
root-post leaving just the highest ranking one.  You do this using
Xapian::Enquire::set_collapse_key() with the value number that holds the
root post unique id.

So pick a non-negative value for the rootid.  If you aren't using values
yet, it might as well be 0:

#define VALUE_ROOTID 0

At index time:

doc.add_value(VALUE_ROOTID, rootid);

At search time:

enquire.set_collapse_key(VALUE_ROOTID);

Cheers,
    Olly