[Xapian-devel] FLAG_PARTIAL and subset words

[Olly Betts]

On Mon, May 16, 2011 at 09:34:39AM +0200, Greg wrote:
> I'll try and create a new database containing only 2 items "volvo v90"
> and "volvo s60" as far as I understand searching for "volvo v" should
> return one result and "volvo" two.

The "v" would expand to "v90 SYNONYM volvo", so "volvo v" would return 2
results.  SYNONYM is OR, but with a different weighting, so ignoring the
weights, "volvo v" is "volvo AND (v90 OR volvo)" which (again ignoring
weights) is the same as just "volvo".

The only difference you might see between "volvo v" and "volvo" is in
the order in which the documents are returned.

If the "v" expands to a lot of terms with a high combined frequency,
then the synonym operator will tend to result in "v" contributing rather
less weight than "volvo" does, so "volvo" will tend to dominate the
ordering.

Cheers,
    Olly