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From "Hoss Man (JIRA)" <>
Subject [jira] Commented: (LUCENE-588) Escaped wildcard character in wildcard term not handled correctly
Date Fri, 30 Nov 2007 02:31:43 GMT


Hoss Man commented on LUCENE-588:

you're refering to the documentation for the querysyntax, used by the QueryParser ... which
is in fact true: you can \ escape both * and ? as far as the QueryParser goes -- but the WildcardQuery
class doesn't support (nor does it's documentation advertise) any escape characters.

In a nut shell: you can escape the characters so QueryParser doesn't consider them wildcards
-- which will influence whether or not QP builds a WIldcardQuery or a TermQuery, but WildcardQuery
doesn't know or care about escape characters.

Consider these examples, and assume a whitespace analyzer....
parse("lucene") -> new TermQuery("lucene")
parse("lu?ene") -> new WIldcardQuery("lu?ene")
parse("lu\?ene") -> new TermQuery("lu?ene")
parse("lu\?e?e") -> new WIldcardQuery("lu?e?e")
parse("lu\?e\?e") -> new TermQuery("lu?e?e")
that's why it works the way it does.

as for how to improve it: It seems reasonable for WildcardQuery to have a boolean constructor
arg indicating whether or not it should respect "standard" backslash escape sequences ...
and then QueryParser could have an option to pass the "raw" string (with escapes) to this
new constructor.

> Escaped wildcard character in wildcard term not handled correctly
> -----------------------------------------------------------------
>                 Key: LUCENE-588
>                 URL:
>             Project: Lucene - Java
>          Issue Type: Bug
>          Components: QueryParser
>    Affects Versions: 2.0.0
>         Environment: Windows XP SP2
>            Reporter: Sunil Kamath
> If an escaped wildcard character is specified in a wildcard query, it is treated as a
wildcard instead of a literal.
> e.g., t\??t is converted by the QueryParser to t??t - the escape character is discarded.

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