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Elastic Docs ›Painless Scripting Language [8.15] ›Painless Language Specification

Regexes

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Regexes

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Regular expression constants are directly supported. To ensure fast performance, this is the only mechanism for creating patterns. Regular expressions are always constants and compiled efficiently a single time.

Pattern p = /[aeiou]/

A poorly written regular expression can significantly slow performance. If possible, avoid using regular expressions, particularly in frequently run scripts.

Pattern flags

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You can define flags on patterns in Painless by adding characters after the trailing / like /foo/i or /foo \w #comment/iUx. Painless exposes all of the flags from Java’s Pattern class using these characters:

Character Java Constant Example

c

CANON_EQ

'å' ==~ /å/c (open in hex editor to see)

i

CASE_INSENSITIVE

'A' ==~ /a/i

l

LITERAL

'[a]' ==~ /[a]/l

m

MULTILINE

'a\nb\nc' =~ /^b$/m

s

DOTALL (aka single line)

'a\nb\nc' =~ /.b./s

U

UNICODE_CHARACTER_CLASS

'Ɛ' ==~ /\\w/U

u

UNICODE_CASE

'Ɛ' ==~ /ɛ/iu

x

COMMENTS (aka extended)

'a' ==~ /a #comment/x
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