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From "Grant Ingersoll (JIRA)" <>
Subject [jira] Commented: (SOLR-1321) Support for efficient leading wildcards search
Date Wed, 12 Aug 2009 16:23:14 GMT


Grant Ingersoll commented on SOLR-1321:

Also no need to do the string round trip in the reverse method, right?  See the ReverseStringFilter
in Lucene contrib/analysis.  Perhaps we should just patch that and add some config options
to it?  Then all Solr would need is the QP change and the FilterFactory change, no?

> Support for efficient leading wildcards search
> ----------------------------------------------
>                 Key: SOLR-1321
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>          Components: Analysis
>    Affects Versions: 1.4
>            Reporter: Andrzej Bialecki 
>            Assignee: Grant Ingersoll
>             Fix For: 1.4
>         Attachments: wildcards-2.patch, wildcards.patch
> This patch is an implementation of the "reversed tokens" strategy for efficient leading
wildcards queries.
> ReversedWildcardsTokenFilter reverses tokens and returns both the original token (optional)
and the reversed token (with positionIncrement == 0). Reversed tokens are prepended with a
marker character to avoid collisions between legitimate tokens and the reversed tokens - e.g.
"DNA" would become "and", thus colliding with the regular term "and", but with the marker
character it becomes "\u0001and".
> This TokenFilter can be added to the analyzer chain that it used during indexing.
> SolrQueryParser has been modified to detect the presence of such fields in the current
schema, and treat them in a special way. First, SolrQueryParser examines the schema and collects
a map of fields where these reversed tokens are indexed. If there is at least one such field,
it also sets QueryParser.setAllowLeadingWildcards(true). When building a wildcard query (in
getWildcardQuery) the term text may be optionally reversed to put wildcards further along
the term text. This happens when the field uses the reversing filter during indexing (as detected
above), AND if the wildcard characters are either at 0-th or 1-st position in the term. Otherwise
the term text is processed as before, i.e. turned into a regular wildcard query.
> Unit tests are provided to test the TokenFilter and the query parsing.

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