Is this a reasonable way to boost?

[Michael Tracey <mt...@biblio.com>]

I'm trying to boost results slightly on a price (not currency) field that are closer to a certain value.  I want results that are not too expensive or too inexpensive to be favored.  Here is what we currently are trying:

bf=sub(1,abs(sub(15,price)))^0.2

where 15 is that "median" I want to boost towards.  Is this a good way?  I understand in older solr's it was common to use recip(ord()) for this but you shouldn't do so now.

Thanks for any comments or advice on improving this.

M.

Re: Is this a reasonable way to boost?

[Chris Hostetter <ho...@fucit.org>]

: > I'm trying to boost results slightly on a price (not currency) field that
: > are closer to a certain value.  I want results that are not too expensive
: > or too inexpensive to be favored.  Here is what we currently are trying:
: > 
: > bf=sub(1,abs(sub(15,price)))^0.2

Hmm... using sub() for your outher most function doesn't make sense to me 
... i think (based on the description of your goal) that you really want 
to be using div() there.

I would also suggest that in general, using "bf" (which gives an additive 
boost) probably isn't a good idea in 90% of the cases where you want to 
boost something ... a multiplicitive boost using the "boost" param of 
edismax, or wrapping your whole query in a {!boost} parser, is going to 
make a lot more sense.

: What I would say though, is that if you have a lot of documents in your
: index, consider pre-computing that field at index time, and boost on the
: pre-computed value, as that will give you better performance.

This, in general, is great advice: anything you can pre-compute at index 
time will save you processing/time at request time. But the caveat i would 
like to point out is that with the query time function approach, the 
"constant" (in this case 15) can actually be varried on a per user basis 
-- ie: you can boost things differnetly for differnet people based on what 
you know about them, either by explicitly asking them, or by analytics of 
their past behavior.


I tried to cover all of these ideas here...

https://people.apache.org/~hossman/ac2012eu/
http://vimeopro.com/user11514798/apache-lucene-eurocon-2012/video/55822630





-Hoss

Re: Is this a reasonable way to boost?

[Upayavira <uv...@odoko.co.uk>]

On Thu, Nov 7, 2013, at 10:51 PM, Michael Tracey wrote:
> I'm trying to boost results slightly on a price (not currency) field that
> are closer to a certain value.  I want results that are not too expensive
> or too inexpensive to be favored.  Here is what we currently are trying:
> 
> bf=sub(1,abs(sub(15,price)))^0.2
> 
> where 15 is that "median" I want to boost towards.  Is this a good way? 
> I understand in older solr's it was common to use recip(ord()) for this
> but you shouldn't do so now.
> 
> Thanks for any comments or advice on improving this.

I think this is a case of "if it works". If it works for you, then
great.

What I would say though, is that if you have a lot of documents in your
index, consider pre-computing that field at index time, and boost on the
pre-computed value, as that will give you better performance.

Upayavira