Ferret talk - Oct 2006 - Setting the boost field after indexing

I was wondering about the potential impact of setting the boost field for an
index after the index has been created and optimized.

I know that some field_info settings can''t really be modified, such as
:store or :tokenize, as they really apply when you are indexing, but is
boost?  If boost is only used for searching, can it be modified dynamically
when searching?

Thanks for any thoughts.

On 10/17/06, peter <peter at ioffer.com> wrote:
> I was wondering about the potential impact of setting the boost field for
an
> index after the index has been created and optimized.
>
> I know that some field_info settings can''t really be modified,
such as
> :store or :tokenize, as they really apply when you are indexing, but is
> boost?  If boost is only used for searching, can it be modified dynamically
> when searching?
>
> Thanks for any thoughts.
Hi Peter,

If you want to set boosts at search time you can set the boost on the
query. For example:

    +title:ferret^20.0 +content:ruby content:rails^0.1

Does that solve your problem? Otherwise, changing the boost on fields
is just as problematic as changing the :store or :tokenized values. At
indexing time the the global field boost, the local field boost, the
document boost and the field length normalization factor are all
multiplied together to get a single normalization factor for that
field. This value is then encoded as a single byte and stored in the
norm file (which you can omit to save space by setting :index =>
:untokenized_omit_norms). This saves a lot of work at search time but
it also makes it impossible to change the global field boost value at
search time.

Anyway, I hope this clears things up and the query boosting does what
you need it to.

Cheers,
Dave