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