Most approaches I have seen to this involve caching results and/or
duplicating the facet information in an alternate data store.
The best resource I have seen using caching results. It permits
you to
drill down into multiple facets and get the no. of documents per
facet
updated easily without going back to the Lucene engine multiple
queries.
http://www.devatwork.nl/index.php/articles/lucenenet/faceted-search-and-drill-down-lucenenet/
1) at initialisation (and/or at set points) step through all the
potential
facet values and store the matching results in some kind of cached
dictionary of bit arrays
2) the user drills down into whatever facets
3) you AND together the bit arrays representing each facet the
user is in
4) You count the number of positive bits in the resulting bit
array to get
the number of articles matched.
At 3) you could clearly AND this together with any other Lucene
result set
to get accurate counts when you are integrating facets and non-
faceted
search results.
The approach works best the higher the ratio of queries to updates
- it
will work poorly for applications with any or all of
a) very frequent updating
b) the need for facets to be 100% accurate in real time
c) a large number of potential facet values (initialisation could
be very
slow)
With a little extra work on the indexing end you could conquer a)
and b)
and hopefully get round the need to reinitialise from scratch.
I'm not sure how well it would work with very large datasets either,
particularly where the number of matches in some facet is very
large - I've
never had to work with bit arrays of millions of bits!
I like this approach because it is a 100% lucene solution and it is
(relatively) fast compared to your approach so far and other similar
approaches.
Faceting is such a common meme for search, I can foresee someone
porting
faceting functionality into the back end if indeed it is not already
happening?
Yours,
Moray
-------------------------------------
Moray McConnachie
Director of IT +44 1865 261 600
Oxford Analytica http://www.oxan.com
-----Original Message-----
From: André Maldonado [mailto:andre.maldon...@gmail.com]
Sent: 09 November 2009 12:44
To: lucene-net-user@incubator.apache.org
Subject: Category count.
Hy all. I have a problem that is exactly like this (that was wrote
from
another developer)
"I am trying to use Lucene Java 2.3.2 to implement search on a
catalog of
products. Apart from the regular fields for a product, there is
field called
'Category'. A product can fall in multiple categories. Currently,
I use
FilteredQuery to search for the same search term with every
Category to get
the number of results per category.
This results in 20-30 internal search calls per query to display the
results. This is slowing down the search considerably. Is there a
faster way
of achieving the same result using Lucene?"
But in the thread that I found this question, I didn't found any
good
solution.
Can you help me?
Thank's
"Então aproximaram-se os que estavam no barco, e adoraram-no,
dizendo: És
verdadeiramente o Filho de Deus." (Mateus 14:33)
