Context-Sensitive Spelling Suggestions & Collations
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Key: SOLR-2585
URL: https://issues.apache.org/jira/browse/SOLR-2585
Project: Solr
Issue Type: Improvement
Components: spellchecker
Affects Versions: 4.0
Reporter: James Dyer
Priority: Minor
Solr currently cannot offer what I'm calling here a "context-sensitive"
spelling suggestion. That is, if a user enters one or more words that have
docFrequency > 0, but nevertheless are misspelled, then no suggestions are
offered. Currently, Solr will always consider a word "correctly spelled" if it
is in the index and/or dictionary, regardless of context. This issue & patch
add support for context-sensitive spelling suggestions.
See SpellCheckCollatorTest.testContextSensitiveCollate() for a the typical use
case for this functionality. This tests both using IndexBasedSepllChecker and
DirectSolrSpellChecker.
Two new Spelling Parameters were added:
- spellcheck.alternativeTermCount - The count of suggestions to return for
each query term existing in the index and/or dictionary. Presumably, users
will want fewer suggestions for words with docFrequency>0. Also setting this
value turns "on" context-sensitive spell suggestions.
- spellcheck.maxResultsForSuggest - The maximum number of hits the request
can return in order to both generate spelling suggestions and set the
"correctlySpelled" element to "false". For example, if this is set to 5 and
the user's query returns 5 or fewer results, the spellchecker will report
"correctlySpelled=false" and also offer suggestions (and collations if
requested). Setting this greater than zero is useful for creating
"did-you-mean" suggestions for queries that return a low number of hits.
I have also included a test using shards. See additions to
DistributedSpellCheckComponentTest.
In Lucene, SpellChecker.java can already support this functionality (by passing
a null IndexReader and field-name). The DirectSpellChecker, however, needs a
minor enhancement. This gives the option to allow DirectSpellChecker to return
suggestions for all query terms regardless of frequency.
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