Xapian::QueryParser Syntax

This document describes the query syntax supported by the Xapian::QueryParser class. The syntax is designed to be similar to other web based search engines, so that users familiar with them don't have to learn a whole new syntax.

Operators

AND

expression AND expression matches documents which are matched by both of the subexpressions.

OR

expression OR expression matches documents which are matched by either of the subexpressions.

NOT

expression NOT expression matches documents which are matched by only the first subexpression.

XOR

expression XOR expression matches documents which are matched by one or other of the subexpressions, but not both. XOR is probably a bit esoteric.

Bracketed expressions

You can control the precedence of the boolean operators using brackets. In the query one OR two AND three the AND takes precedence, so this is the same as one OR (two AND three). You can override the precedence using (one OR two) AND three.

+ and -

A group of terms with some marked with + and - will match documents containing all of the + terms, but none of the - terms. Terms not marked with + or - contribute towards the document rankings. You can also use + and - on phrases and on bracketed expressions.

NEAR

one NEAR two NEAR three matches documents containing those words within 10 words of each other.

Phrase searches

A phrase surrounded with double quotes ("") matches documents containing that exact phrase. Hyphenated words are also treated as phrases, as are cases such as filenames and email addresses (e.g. /etc/passwd or president@whitehouse.gov).

Searching within a probabilistic field

If the database has been indexed with prefixes on probabilistic terms from certain fields, you can set up a prefix map so that the user can search within those fields. For example author:dickens title:shop might find documents by dickens with shop in the title. You can also specify a prefix on a quoted phrase or on a bracketed expression.

Searching for proper names

If the databases has been indexed with capitalised words producing R-prefixed terms from the unstemmed words, then searching for a capitalised word will match the unstemmed form.

Searching for already stemmed forms

A term which ends with a dot is assumed to be already stemmed. This isn't useful for users, but omega uses it sometimes for terms added from topterms.

Wildcards

The QueryParser supports using a trailing '*' wildcard, which matches any number of trailing characters, so wildc* would match wildcard, wildcarded, wildcards, wildcat, wildcats, etc. This feature is disabled by default - pass Xapian::QueryParser::FLAG_WILDCARD in the flags argument to Xapian::QueryParser::parse_query() to enable it.