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From "Robert Muir (JIRA)" <>
Subject [jira] Commented: (SOLR-1321) Support for efficient leading wildcards search
Date Fri, 31 Jul 2009 16:47:14 GMT


Robert Muir commented on SOLR-1321:

andrej, i really like this feature.

one question though, the way you have overridden getWildcardQuery() i am not certain how I
can have both this feature and say, override getWildCardQuery to produce an AutomatonWildcardQuery:
what I want is both :) , because AutomatonWildCardQuery cannot help at all with leading *,
(it can with leading ? for example).

but don't let this really get in your way, just a side note.

> Support for efficient leading wildcards search
> ----------------------------------------------
>                 Key: SOLR-1321
>                 URL:
>             Project: Solr
>          Issue Type: Improvement
>          Components: Analysis
>    Affects Versions: 1.4
>            Reporter: Andrzej Bialecki 
>             Fix For: 1.4
>         Attachments: 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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