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From "Mark Harwood (JIRA)" <>
Subject [jira] Commented: (LUCENE-1910) Extension to MoreLikeThis to use tag information
Date Mon, 21 Sep 2009 15:31:00 GMT


Mark Harwood commented on LUCENE-1910:

Hi Thomas,
Following your request for feedback, some initial thoughts from a very quick look.

* The "Information Gain" algo could use a little more explanation e.g. using variable names
other than "num1" and "num2" and could perhaps be extracted into a utility class

* Is this scalable? It looks like in initialize it is loading this:
      * All terms in the index
	protected HashSet docTerms=new HashSet();
..that seems a little scary!
It's also doing a seperate BooleanQuery for all items in this list ( and repeated for >1
tag?). Thats look like a lot of searches.

I need to spend a little more time looking at it before I understand it in more detail.
Before then - have you tested this on a big (millions of docs/terms) index? Some performance
figures would be useful to accompany this.


> Extension to MoreLikeThis to use tag information
> ------------------------------------------------
>                 Key: LUCENE-1910
>                 URL:
>             Project: Lucene - Java
>          Issue Type: New Feature
>          Components: contrib/*
>            Reporter: Thomas D'Silva
>            Priority: Minor
>         Attachments: LUCENE-1910.patch
> I would like to contribute a class based on the MoreLikeThis class in
> contrib/queries that generates a query based on the tags associated
> with a document. The class assumes that documents are tagged with a
> set of tags (which are stored in the index in a seperate Field). The
> class determines the top document terms associated with a given tag
> using the information gain metric.
> While generating a MoreLikeThis query for a document the tags
> associated with document are used to determine the terms in the query.
> This class is useful for finding similar documents to a document that
> does not have many relevant terms but was tagged.

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