224 lines
4.8 KiB
Plaintext
224 lines
4.8 KiB
Plaintext
[[regexp-syntax]]
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== Regular expression syntax
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A https://en.wikipedia.org/wiki/Regular_expression[regular expression] is a way to
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match patterns in data using placeholder characters, called operators.
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{es} supports regular expressions in the following queries:
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* <<query-dsl-regexp-query, `regexp`>>
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* <<query-dsl-query-string-query, `query_string`>>
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{es} uses https://lucene.apache.org/core/[Apache Lucene]'s regular expression
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engine to parse these queries.
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[float]
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[[regexp-reserved-characters]]
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=== Reserved characters
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Lucene's regular expression engine supports all Unicode characters. However, the
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following characters are reserved as operators:
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....
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. ? + * | { } [ ] ( ) " \
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....
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Depending on the <<regexp-optional-operators, optional operators>> enabled, the
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following characters may also be reserved:
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....
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# @ & < > ~
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....
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To use one of these characters literally, escape it with a preceding
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backslash or surround it with double quotes. For example:
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....
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\@ # renders as a literal '@'
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\\ # renders as a literal '\'
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"john@smith.com" # renders as 'john@smith.com'
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....
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[float]
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[[regexp-standard-operators]]
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=== Standard operators
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Lucene's regular expression engine does not use the
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https://en.wikipedia.org/wiki/Perl_Compatible_Regular_Expressions[Perl
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Compatible Regular Expressions (PCRE)] library, but it does support the
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following standard operators.
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`.`::
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+
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--
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Matches any character. For example:
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....
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ab. # matches 'aba', 'abb', 'abz', etc.
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....
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--
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`?`::
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+
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--
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Repeat the preceding character zero or one times. Often used to make the
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preceding character optional. For example:
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....
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abc? # matches 'ab' and 'abc'
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....
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--
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`+`::
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+
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--
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Repeat the preceding character one or more times. For example:
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....
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ab+ # matches 'abb', 'abbb', 'abbbb', etc.
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....
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--
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`*`::
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+
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--
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Repeat the preceding character zero or more times. For example:
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....
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ab* # matches 'ab', 'abb', 'abbb', 'abbbb', etc.
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....
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--
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`{}`::
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+
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--
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Minimum and maximum number of times the preceding character can repeat. For
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example:
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....
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a{2} # matches 'aa'
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a{2,4} # matches 'aa', 'aaa', and 'aaaa'
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a{2,} # matches 'a` repeated two or more times
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....
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--
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`|`::
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+
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--
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OR operator. The match will succeed if the longest pattern on either the left
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side OR the right side matches. For example:
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....
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abc|xyz # matches 'abc' and 'xyz'
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....
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--
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`( … )`::
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+
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--
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Forms a group. You can use a group to treat part of the expression as a single
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character. For example:
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....
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abc(def)? # matches 'abc' and 'abcdef' but not 'abcd'
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....
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--
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`[ … ]`::
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+
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--
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Match one of the characters in the brackets. For example:
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....
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[abc] # matches 'a', 'b', 'c'
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....
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Inside the brackets, `-` indicates a range unless `-` is the first character or
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escaped. For example:
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....
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[a-c] # matches 'a', 'b', or 'c'
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[-abc] # '-' is first character. Matches '-', 'a', 'b', or 'c'
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[abc\-] # Escapes '-'. Matches 'a', 'b', 'c', or '-'
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....
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A `^` before a character in the brackets negates the character or range. For
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example:
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....
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[^abc] # matches any character except 'a', 'b', or 'c'
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[^a-c] # matches any character except 'a', 'b', or 'c'
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[^-abc] # matches any character except '-', 'a', 'b', or 'c'
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[^abc\-] # matches any character except 'a', 'b', 'c', or '-'
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....
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--
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[float]
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[[regexp-optional-operators]]
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=== Optional operators
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You can use the `flags` parameter to enable more optional operators for
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Lucene's regular expression engine.
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To enable multiple operators, use a `|` separator. For example, a `flags` value
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of `COMPLEMENT|INTERVAL` enables the `COMPLEMENT` and `INTERVAL` operators.
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[float]
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==== Valid values
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`ALL` (Default)::
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Enables all optional operators.
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`COMPLEMENT`::
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+
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--
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Enables the `~` operator. You can use `~` to negate the shortest following
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pattern. For example:
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....
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a~bc # matches 'adc' and 'aec' but not 'abc'
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....
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--
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`INTERVAL`::
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+
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--
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Enables the `<>` operators. You can use `<>` to match a numeric range. For
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example:
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....
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foo<1-100> # matches 'foo1', 'foo2' ... 'foo99', 'foo100'
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foo<01-100> # matches 'foo01', 'foo02' ... 'foo99', 'foo100'
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....
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--
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`INTERSECTION`::
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+
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--
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Enables the `&` operator, which acts as an AND operator. The match will succeed
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if patterns on both the left side AND the right side matches. For example:
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....
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aaa.+&.+bbb # matches 'aaabbb'
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....
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--
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`ANYSTRING`::
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+
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--
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Enables the `@` operator. You can use `@` to match any entire
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string.
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You can combine the `@` operator with `&` and `~` operators to create an
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"everything except" logic. For example:
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....
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@&~(abc.+) # matches everything except terms beginning with 'abc'
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....
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--
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[float]
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[[regexp-unsupported-operators]]
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=== Unsupported operators
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Lucene's regular expression engine does not support anchor operators, such as
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`^` (beginning of line) or `$` (end of line). To match a term, the regular
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expression must match the entire string. |