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https://issues.apache.org/jira/browse/SOLR-2010?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12916533#action_12916533
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James Dyer commented on SOLR-2010:
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Grant,
It wouldn't be difficult to create an uber-patch that allows users to pick
which way to go. If that's the route you want to go then I'd be happy to do
that. However, I think it would be best to stick with the "recombine" approach
because although you'll get throw-away collations, it will always be done
internally within the shard. The performance penalty in most cases will be
slight. On the other hand, if using the "Search Handler" approach, it has to
query over the network for each *try*, which could be significant. I wouldn't
say that you would never benefit from the "Search Handler" option, but I wonder
if it warrants extra lines of code and making changes to the SearchHandler
class, etc.
Unfortunately I haven't done any performance testing with these. We only are in
early development here with SOLR and I don't have access to multiple servers
with which I can easily deploy such a test. On a non-distributed setup this
patch only adds a little bit of overhead, and I wouldn't expect the "recombine"
option to be much worse than that.
Note that with either approach I'd imagine you'd frequently run into the case
where some/many shards simply do not have the documents the user is looking for
and they will have to query up to "collationMaxTries" to come up empty. In
which case the shard(s) that get the results may need to wait for the shards
that are busy querying away in vain...
Let me know if you want an "uber-patch". I might have a little time later today
if you let me know.
> Improvements to SpellCheckComponent Collate functionality
> ---------------------------------------------------------
>
> Key: SOLR-2010
> URL: https://issues.apache.org/jira/browse/SOLR-2010
> Project: Solr
> Issue Type: New Feature
> Components: clients - java, spellchecker
> Affects Versions: 1.4.1
> Environment: Tested against trunk revision 966633
> Reporter: James Dyer
> Assignee: Grant Ingersoll
> Priority: Minor
> Attachments: SOLR-2010.patch, SOLR-2010.patch, SOLR-2010.patch,
> SOLR-2010.patch, SOLR-2010.txt, SOLR-2010_141.patch,
> SOLR-2010_shardRecombineCollations_993538.patch,
> SOLR-2010_shardRecombineCollations_999521.patch,
> SOLR-2010_shardSearchHandler_993538.patch,
> SOLR-2010_shardSearchHandler_999521.patch
>
>
> Improvements to SpellCheckComponent Collate functionality
> Our project requires a better Spell Check Collator. I'm contributing this as
> a patch to get suggestions for improvements and in case there is a broader
> need for these features.
> 1. Only return collations that are guaranteed to result in hits if re-queried
> (applying original fq params also). This is especially helpful when there is
> more than one correction per query. The 1.4 behavior does not verify that a
> particular combination will actually return hits.
> 2. Provide the option to get multiple collation suggestions
> 3. Provide extended collation results including the # of hits re-querying
> will return and a breakdown of each misspelled word and its correction.
> This patch is similar to what is described in SOLR-507 item #1. Also, this
> patch provides a viable workaround for the problem discussed in SOLR-1074. A
> dictionary could be created that combines the terms from the multiple fields.
> The collator then would prune out any spurious suggestions this would cause.
> This patch adds the following spellcheck parameters:
> 1. spellcheck.maxCollationTries - maximum # of collation possibilities to try
> before giving up. Lower values ensure better performance. Higher values may
> be necessary to find a collation that can return results. Default is 0,
> which maintains backwards-compatible behavior (do not check collations).
> 2. spellcheck.maxCollations - maximum # of collations to return. Default is
> 1, which maintains backwards-compatible behavior.
> 3. spellcheck.collateExtendedResult - if true, returns an expanded response
> format detailing collations found. default is false, which maintains
> backwards-compatible behavior. When true, output is like this (in context):
> <lst name="spellcheck">
> <lst name="suggestions">
> <lst name="hopq">
> <int name="numFound">94</int>
> <int name="startOffset">7</int>
> <int name="endOffset">11</int>
> <arr name="suggestion">
> <str>hope</str>
> <str>how</str>
> <str>hope</str>
> <str>chops</str>
> <str>hoped</str>
> etc
> </arr>
> <lst name="faill">
> <int name="numFound">100</int>
> <int name="startOffset">16</int>
> <int name="endOffset">21</int>
> <arr name="suggestion">
> <str>fall</str>
> <str>fails</str>
> <str>fail</str>
> <str>fill</str>
> <str>faith</str>
> <str>all</str>
> etc
> </arr>
> </lst>
> <lst name="collation">
> <str name="collationQuery">Title:(how AND fails)</str>
> <int name="hits">2</int>
> <lst name="misspellingsAndCorrections">
> <str name="hopq">how</str>
> <str name="faill">fails</str>
> </lst>
> </lst>
> <lst name="collation">
> <str name="collationQuery">Title:(hope AND faith)</str>
> <int name="hits">2</int>
> <lst name="misspellingsAndCorrections">
> <str name="hopq">hope</str>
> <str name="faill">faith</str>
> </lst>
> </lst>
> <lst name="collation">
> <str name="collationQuery">Title:(chops AND all)</str>
> <int name="hits">1</int>
> <lst name="misspellingsAndCorrections">
> <str name="hopq">chops</str>
> <str name="faill">all</str>
> </lst>
> </lst>
> </lst>
> </lst>
> In addition, SOLRJ is updated to include
> SpellCheckResponse.getCollatedResults(), which will return the expanded
> Collation format. getCollatedResult(), which returns a single String, is
> retained for backwards-compatibility. Other APIs were not changed but will
> still work provided that spellcheck.collateExtendedResult is false.
> This likely will not return valid results if using Shards. Rather, a more
> robust interaction with the index would be necessary than what exists in
> SpellCheckCollator.collate().
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