[Xapian-discuss] Search::Xapian add_database'd search results are odd?

[Olly Betts]

On Tue, Dec 21, 2004 at 01:32:13PM -0800, Eric Parusel wrote:
> Anyways, I've been testing out using $db->add_database() when searching, 
> and it seems like the docids I'm getting out of it are incorrect, almost 
> as though they're "double" what they should be (numerically)...
> 
> the docids that exist should be around 950,000 and 1000000 not around 
> 1900000, etc...

If you search over more than one database, the docids in the underlying
databases are mapped to avoid collisions.

The mapping is (at least currently):

    did_merged = (did_raw - 1) * number_of_databases + offset

where offset ranges from 1 to number_of_databases.

You can generally just treat did_merged as an opaque value and use it
with the combined database to retrieve the appropriate document.

Cheers,
    Olly