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https://issues.apache.org/jira/browse/SOLR-4381?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nolan Lawson updated SOLR-4381:
-------------------------------
Attachment: SOLR-4381-2.patch
Thanks for the guidance, Steve. The attached SOLR-4381-2.patch should work for
Solr 4.1.0.
> Query-time multi-word synonym expansion
> ---------------------------------------
>
> Key: SOLR-4381
> URL: https://issues.apache.org/jira/browse/SOLR-4381
> Project: Solr
> Issue Type: Improvement
> Components: query parsers
> Reporter: Nolan Lawson
> Priority: Minor
> Labels: multi-word, queryparser, synonyms
> Fix For: 4.2, 5.0
>
> Attachments: SOLR-4381-2.patch, SOLR-4381.patch
>
>
> This is an issue that seems to come up perennially.
> The [Solr
> docs|http://wiki.apache.org/solr/AnalyzersTokenizersTokenFilters#solr.SynonymFilterFactory]
> caution that index-time synonym expansion should be preferred to query-time
> synonym expansion, due to the way multi-word synonyms are treated and how IDF
> values can be boosted artificially. But query-time expansion should have huge
> benefits, given that changes to the synonyms don't require re-indexing, the
> index size stays the same, and the IDF values for the documents don't get
> permanently altered.
> The proposed solution is to move the synonym expansion logic from the
> analysis chain (either query- or index-type) and into a new QueryParser. See
> the attached patch for an implementation.
> The core Lucene functionality is untouched. Instead, the EDismaxQParser is
> extended, and synonym expansion is done on-the-fly. Queries are parsed into
> a lattice (i.e. all possible synonym combinations), while individual
> components of the query are still handled by the EDismaxQParser itself.
> It's not an ideal solution by any stretch. But it's nice and self-contained,
> so it invites experimentation and improvement. And I think it fits in well
> with the merry band of misfit query parsers, like {{func}} and {{frange}}.
> More details about this solution can be found in [this blog
> post|http://nolanlawson.com/2012/10/31/better-synonym-handling-in-solr/] and
> [the Github page for the
> code|https://github.com/healthonnet/hon-lucene-synonyms].
> At the risk of tooting my own horn, I also think this patch sufficiently
> fixes SOLR-3390 (highlighting problems with multi-word synonyms) and
> LUCENE-4499 (better support for multi-word synonyms).
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