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https://issues.apache.org/jira/browse/LUCENE-6459?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Areek Zillur updated LUCENE-6459:
---------------------------------
    Attachment: LUCENE-6459.patch

Updated patch:
 - added test querying empty contexts with boosts
 - add context to FSTPath.toString

> [suggest] Query Interface for suggest API
> -----------------------------------------
>
>                 Key: LUCENE-6459
>                 URL: https://issues.apache.org/jira/browse/LUCENE-6459
>             Project: Lucene - Core
>          Issue Type: New Feature
>          Components: core/search
>    Affects Versions: 5.1
>            Reporter: Areek Zillur
>            Assignee: Areek Zillur
>             Fix For: Trunk, 5.x, 5.1
>
>         Attachments: LUCENE-6459.patch, LUCENE-6459.patch, LUCENE-6459.patch, 
> LUCENE-6459.patch
>
>
> This patch factors out common indexing/search API used by the recently 
> introduced [NRTSuggester|https://issues.apache.org/jira/browse/LUCENE-6339]. 
> The motivation is to provide a query interface for FST-based fields 
> (*SuggestField* and *ContextSuggestField*) for enabling suggestion scoring 
> and more powerful automaton queries. 
> Previously, only prefix ‘queries’ with index-time weights were supported but 
> we can also support:
> * Prefix queries expressed as regular expressions:  get suggestions that 
> match multiple prefixes
>       ** Example: _star\[wa\|tr\]_ matches _starwars_ and _startrek_
> * Fuzzy Prefix queries supporting scoring: get typo tolerant suggestions 
> scored by how close they are to the query prefix
>     ** Example: querying for _seper_ will score _separate_ higher then 
> _superstitious_
> * Context Queries: get suggestions boosted and/or filtered based on their 
> indexed contexts (meta data)
>     ** Example: get typo tolerant suggestions on song names with prefix _like 
> a roling_ boosting songs with genre _rock_ and _indie_
>     ** Example: get suggestion on all file names starting with _finan_ only 
> for _user1_ and _user2_
> h3. Suggest API
> {code}
> SuggestIndexSearcher searcher = new SuggestIndexSearcher(reader);
> CompletionQuery query = ...
> TopSuggestDocs suggest = searcher.suggest(query, num);
> {code}
> h3. CompletionQuery
> *CompletionQuery* is used to query *SuggestField* and *ContextSuggestField*. 
> A *CompletionQuery* produces a *CompletionWeight*, which allows 
> *CompletionQuery* implementations to pass in an automaton that will be 
> intersected with a FST and allows boosting and meta data extraction from the 
> intersected partial paths. A *CompletionWeight* produces a 
> *CompletionScorer*. A *CompletionScorer* executes a Top N search against the 
> FST with the provided automaton, scoring and filtering all matched paths. 
> h4. PrefixCompletionQuery
> Return documents with values that match the prefix of an analyzed term text 
> Documents are sorted according to their suggest field weight. 
> {code}
> PrefixCompletionQuery(Analyzer analyzer, Term term)
> {code}
> h4. RegexCompletionQuery
> Return documents with values that match the prefix of a regular expression
> Documents are sorted according to their suggest field weight.
> {code}
> RegexCompletionQuery(Term term)
> {code}
> h4. FuzzyCompletionQuery
> Return documents with values that has prefixes within a specified edit 
> distance of an analyzed term text.
> Documents are ‘boosted’ by the number of matching prefix letters of the 
> suggestion with respect to the original term text.
> {code}
> FuzzyCompletionQuery(Analyzer analyzer, Term term)
> {code}
> h5. Scoring
> {{suggestion_weight + (global_maximum_weight * boost)}}
> where {{suggestion_weight}}, {{global_maximum_weight}} and {{boost}} are all 
> integers. 
> {{boost = # of prefix characters matched}}
> h4. ContextQuery
> Return documents that match a {{CompletionQuery}} filtered and/or boosted by 
> provided context(s). 
> {code}
> ContextQuery(CompletionQuery query)
> contextQuery.addContext(CharSequence context, int boost, boolean exact)
> {code}
> *NOTE:* {{ContextQuery}} should be used with {{ContextSuggestField}} to query 
> suggestions boosted and/or filtered by contexts
> h5. Scoring
> {{suggestion_weight + (global_maximum_weight * context_boost)}}
> where {{suggestion_weight}}, {{global_maximum_weight}} and {{context_boost}} 
> are all integers
> When used with {{FuzzyCompletionQuery}},
> {{suggestion_weight + (global_maximum_weight * (context_boost + 
> fuzzy_boost))}}
> h3. Context Suggest Field
> To use {{ContextQuery}}, use {{ContextSuggestField}} instead of 
> {{SuggestField}}. Any {{CompletionQuery}} can be used with 
> {{ContextSuggestField}}, the default behaviour is to return suggestions from 
> *all* contexts. {{Context}} for every completion hit can be accessed through 
> {{SuggestScoreDoc#context}}.
> {code}
> ContextSuggestField(String name, Collection<CharSequence> contexts, String 
> value, int weight) 
> {code}



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