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From "Andrzej Bialecki (JIRA)" <>
Subject [jira] Commented: (SOLR-1321) Support for efficient leading wildcards search
Date Wed, 12 Aug 2009 21:03:14 GMT


Andrzej Bialecki  commented on SOLR-1321:

bq. FWIW, it also seemed like the reverse code in ReverseStringFilter was faster than the
patch, but I didn't compare quantitatively.

It better be - it can reverse in-place, while we have to allocate a new buffer because of
the marker char in front. That's what I meant by messy code - we would need both the in-place
and the out-of-place method depending on an option.

> 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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