On 12/14/06, Derek Watson <[EMAIL PROTECTED]> wrote:
I have been developing a new search application based on Solr (Very
nice!) using dismax. We are using query-time boosts to provide better
search results for user queries and index-time boosts to promote
certain documents over others.
My question is about the latter: We have a "position" field available
at index time that is an integer value, 0 being the 1st position, 1
being the 2nd position, 99 being the hundredth, etc. How do I get
Solr to return documents in that same order?
If you want documents returned in the same order as a field, it's
easy... you sort!
If you want the value of a field to influence a score, not determine
the exact sort order, you can use FunctionQuery (currently hacked into
the query parser as _val_:myfield)
Is it possible to apply a
negative boost?
<doc boost="-0.0">...</doc>
<doc boost="-0.1">...</doc>
<doc boost="-0.2">...</doc>
I notice in the documentation for parseFieldBoosts that the routine
"Doesn't care if boost info is negative, you're on your own.", but
what does that mean?
AFAIK, negative scores and boosts at query time aren't really
prohibited in Lucene, but neither are they really supported. I would
avoid them.
Negative boosts would be mapped to zero boosts during indexing... this
is due to the way norms are represented in the Lucene index:
http://svn.apache.org/viewvc/lucene/java/trunk/src/java/org/apache/lucene/util/SmallFloat.java?view=markup
Note that there are only 3 mantissa bits in the 8 bit float, so small
distinctions at index time are effectively discarded.
-Yonik
