Wildcards

All words entered in Recoll search fields will be processed for wildcard expansion before the request is finally executed.

The wildcard characters are:

  • * which matches 0 or more characters.

  • ? which matches a single character.

  • [] which allow defining sets of characters to be matched (ex: [abc] matches a single character which may be 'a' or 'b' or 'c', [0-9] matches any number.

You should be aware of a few things when using wildcards.

  • Using a wildcard character at the beginning of a word can make for a slow search because Recoll will have to scan the whole index term list to find the matches. However, this is much less a problem for field searches, and queries like author:*@domain.com can sometimes be very useful.

  • For Recoll version 18 only, when working with a raw index (preserving character case and diacritics), the literal part of a wildcard expression will be matched exactly for case and diacritics. This is not true any more for versions 19 and later.

  • Using a * at the end of a word can produce more matches than you would think, and strange search results. You can use the term explorer tool to check what completions exist for a given term. You can also see exactly what search was performed by clicking on the link at the top of the result list. In general, for natural language terms, stem expansion will produce better results than an ending * (stem expansion is turned off when any wildcard character appears in the term).

Wildcards and path filtering

Due to the way that Recoll processes wildcards inside dir path filtering clauses, they will have a multiplicative effect on the query size. A clause containing wildcards in several paths elements, like, for example, dir:/home/me/*/*/docdir, will almost certainly fail if your indexed tree is of any realistic size.

Depending on the case, you may be able to work around the issue by specifying the paths elements more narrowly, with a constant prefix, or by using 2 separate dir: clauses instead of multiple wildcards, as in dir:/home/me dir:docdir. The latter query is not equivalent to the initial one because it does not specify a number of directory levels, but that's the best we can do (and it may be actually more useful in some cases).

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