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From "Chuck Williams" <ch...@manawiz.com>
Subject RE: How to efficiently get # of search results, per attribute
Date Sat, 13 Nov 2004 23:36:11 GMT
My Lucene application includes multi-faceted navigation that does a more
complex version of the below.  I've got 5 different taxonomies into
which every indexed item is classified.  The largest of the taxonomies
has over 15,000 entries while the other 4 are much smaller. For every
search query, I determine the best small set of nodes from each taxonomy
to present to the user as drill down options, and provide the counts
regarding how many results fall under each of these nodes.  At present I
only have about 25,000 indexed objects and usually no more than 1,000
results from the initial query.  To determine the drill-down options and
counts, I scan up to 1,000 results computing the counts for all nodes
into which these results classify.  Then for each taxonomy I pick the
best drill-down options available (orthogonal set with reasonable
branching factor that covers all results) and present them with their
counts.  If there are more than 1,000 results, I extrapolate the
computed counts to estimate the actual counts on the entire set of
results.  This is all done with a single index and a single search.

The total time required for performing this computation for the one
large taxonomy is under 10ms, running in full debug mode in my ide.  The
query response time overall is subjectively instantaneous at the UI
(Google-speed or better).  So, unless some dimension of the problem is
much bigger than mine, I doubt performance will be an issue.

Chuck

  > -----Original Message-----
  > From: Nader Henein [mailto:nsh@bayt.net]
  > Sent: Saturday, November 13, 2004 2:29 AM
  > To: Lucene Users List
  > Subject: Re: How to efficiently get # of search results, per
attribute
  > 
  > It depends on how many results they're looking through, here are two
  > scenarios I see:
  > 
  > 1] If you don't have that many records you can fetch all the results
and
  > then do a post parsing step the determine totals
  > 
  > 2] If you have a lot of entries in each category and you're worried
  > about fetching thousands of records every time, you can just have
  > seperate indecies per category and search them in in parallel (not
  > Lucene Parallel Search) and you can get up to 100 hits for each one
  > (efficiency) but you'll also have the total from the search to
display.
  > 
  > Either way you can boost up speed using RamDirectory if you need
more
  > speed from the search, but whichever approach you choose I would
  > recommend that you sit down and do some number crunching to figure
out
  > which way to go.
  > 
  > 
  > Hope this helps
  > 
  > Nader Henein
  > 
  > 
  > 
  > Chris Lamprecht wrote:
  > 
  > >I'd like to implement a search across several types of "entities",
  > >let's say, classes, professors, and departments.  I want the user
to
  > >be able to enter a simple, single query and not have to specify
what
  > >they're looking for.  Then I want the search results to be
something
  > >like this:
  > >
  > >Search results for: "philosophy boyer"
  > >
  > >Found: 121 classes - 5 professors - 2 departments
  > >
  > ><search results here...>
  > >
  > >
  > >I know I could iterate through every hit returned and count them up
  > >myself, but that seems inefficient if there are lots of results.
Is
  > >there some other way to get this kind of information from the
search
  > >result set?  My other ideas are: doing a separate search each
result
  > >type, or storing different types in different indexes.  Any
  > >suggestions?  Thanks for your help!
  > >
  > >-Chris
  > >
  >
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  > 
  >
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