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

[Richard Boulton]

On Tue, 2004-12-21 at 18:31 -0800, Eric Parusel wrote:
> I suppose given that the two db's don't have conflicting id's, that 
> executing the query twice on the two db's separately to collect the 
> docids I need might actually be simpler/quicker than combining them and 
> then doing an equation to get each true docid?

Unless you're doing a pure boolean query (ie, unweighted), you'll get
differently ordered results by doing this: when a search is performed
against multiple databases, the database statistics are merged before
calculating the weight of each result.  For example, if a term is
frequent in one database and infrequent in another, a search using that
term would assign a different importance to the term in each database if
searching individually, but would assign the same importance when
searching across databases if searching the combined database.

In any case, the overhead of evaluating the equations Olly suggested is
likely to be a negligible part of the cost of running a search.

-- 
Richard Boulton <richard at tartarus.org>