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From Robert Muir <rcm...@gmail.com>
Subject Re: Superset Similarity?
Date Sat, 17 Nov 2012 07:20:47 GMT
On Fri, Nov 16, 2012 at 5:18 PM, Tom Burton-West <tburtonw@umich.edu> wrote:

> Hi Otis,
>
> I hope this is not off-topic,
>
> Apparently in Lucene similarity does not have to be set at index time:
>

Actually in the general case it does. IndexWriter calls the Similarity's
computeNorm method at index-time.
Its just that the models we added for that GSOC project all have the same
computeNorm implementation at the moment, so they are "compatible".

On the other hand if you want to use something like SweetSpotSimilarity
which has a different computeNorm, then you need to reindex with it.


>
> See http://lucene.apache.org/core/4_0_0/changes/Changes.html under Lucene
> 2959
> "All models default to the same index-time norm encoding as
> DefaultSimilarity, so you can easily try these out/switch back and
> forth/run experiments and comparisons without re-indexing."
>
> Does Solr expose this ability to change similarities without re-indexing?
>  i.e could you just change your schema?
>

yes thats right.

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