Improvements to SpellCheckComponent Collate functionality
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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
Priority: Minor
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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