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https://issues.apache.org/jira/browse/LUCENE-1812?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Doron Cohen updated LUCENE-1812:
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Attachment: pruning.patch
The pruning framework is pretty cool - it is quite easy to add a new pruning
policy!
Initially I planned to focus on CarmelPruningPolicy plus add the more
sophisticated algorithm (tpoK) described in the paper, but eventually found
myself doing more changes - Andrzej, I hope you like the changes - like some
methods I renamed - otherwise please feel free to rename them back.
+Patch Details+
* Documentation changes - mainly moved things to where I thought they belong,
like moving from CarmelPruning to TFPruning the general discussion that applies
to any Term pruning implementation.
* Renamed some of TermPruningPolicy methods for better readability - well, to
me :\) -- hope you agree with the new names, othewise please feel free to
change back.
* Renamed CarmelTermPruningPolicy to CarmelTermPruningUniformPolicy. - quite a
long name... but descriptive, as this an enhanced form of the "uniform" case
from the paper. Modified documentation accordingly.
* Added CarmelTermPruningTopKPolicy - this is the more sophisticated/strong
form of pruning described in the paper. (Test case added.)
* Fixed some compiler warnings (1.5, Lucene.Version..)
* Bug (\?) in CarmelTermPruningPolicy in initTermPositions() - it sorts by
docid before selecting the top subset, but in fact this seems dead code? Added
a "TODO deadcode" there, maybe I am missing something.
* Enabled topK pruning through the PruningTool program (untested)
* Simplified the if statements in PruningRedaer.PruningTermEnum.next() -
hopefully not missing something t here...
There's more to do though not sure when I'll have the cycles..:
* Quality/performance test for the topK pruning algorithm - using LAtimes or
some other judged collection.
Or perhaps Robert can try it on that Persian test collection.
* Add also the "Delta Pruning" policy as described in the paper
* Junit for CarmelTermPruningUniformPolicy
Doron
> Static index pruning by in-document term frequency (Carmel pruning)
> -------------------------------------------------------------------
>
> Key: LUCENE-1812
> URL: https://issues.apache.org/jira/browse/LUCENE-1812
> Project: Lucene - Java
> Issue Type: New Feature
> Components: contrib/*
> Affects Versions: 2.9, 3.1
> Reporter: Andrzej Bialecki
> Attachments: pruning.patch, pruning.patch, pruning.patch,
> pruning.patch
>
>
> This module provides tools to produce a subset of input indexes by removing
> postings data for those terms where their in-document frequency is below a
> specified threshold. The net effect of this processing is a much smaller
> index that for common types of queries returns nearly identical top-N results
> as compared with the original index, but with increased performance.
> Optionally, stored values and term vectors can also be removed. This
> functionality is largely independent, so it can be used without term pruning
> (when term freq. threshold is set to 1).
> As the threshold value increases, the total size of the index decreases,
> search performance increases, and recall decreases (i.e. search quality
> deteriorates). NOTE: especially phrase recall deteriorates significantly at
> higher threshold values.
> Primary purpose of this class is to produce small first-tier indexes that fit
> completely in RAM, and store these indexes using
> IndexWriter.addIndexes(IndexReader[]). Usually the performance of this class
> will not be sufficient to use the resulting index view for on-the-fly pruning
> and searching.
> NOTE: If the input index is optimized (i.e. doesn't contain deletions) then
> the index produced via IndexWriter.addIndexes(IndexReader[]) will preserve
> internal document id-s so that they are in sync with the original index. This
> means that all other auxiliary information not necessary for first-tier
> processing, such as some stored fields, can also be removed, to be quickly
> retrieved on-demand from the original index using the same internal document
> id.
> Threshold values can be specified globally (for terms in all fields) using
> defaultThreshold parameter, and can be overriden using per-field or per-term
> values supplied in a thresholds map. Keys in this map are either field names,
> or terms in field:text format. The precedence of these values is the
> following: first a per-term threshold is used if present, then per-field
> threshold if present, and finally the default threshold.
> A command-line tool (PruningTool) is provided for convenience. At this moment
> it doesn't support all functionality available through API.
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