Regular Expression Functions

Regular expression functions use RE2 as the regex engine. RE2 is fast, but supports only a subset of PCRE syntax and in particular does not support backtracking and associated features (e.g. back references). See https://github.com/google/re2/wiki/Syntax for more information.

Compiling regular expressions is CPU intensive. Hence, each function is limited to 20 different expressions per instance and thread of execution.

like(string, pattern) boolean
like(string, pattern, escape) boolean

Evaluates if the string matches the pattern. Patterns can contain regular characters as well as wildcards. Wildcard characters can be escaped using the single character specified for the escape parameter. Matching is case sensitive.

Note: The wildcard ‘%’ represents 0, 1 or multiple characters and the wildcard ‘_’ represents exactly one character.

Note: Each function instance allow for a maximum of 20 regular expressions to be compiled per thread of execution. Not all patterns require compilation of regular expressions. Patterns ‘aaa’, ‘aaa%’, ‘%aaa’, where ‘aaa’ contains only regular characters and ‘_’ wildcards are evaluated without using regular expressions. Only those patterns that require the compilation of regular expressions are counted towards the limit.

SELECT like(‘abc’, ‘%b%’); – true SELECT like(‘a_c’, ‘%#_%’, ‘#’); – true

regexp_extract(string, pattern) varchar

Returns the first substring matched by the regular expression pattern in string:

SELECT regexp_extract('1a 2b 14m', '\d+'); -- 1
regexp_extract(string, pattern, group) varchar

Finds the first occurrence of the regular expression pattern in string and returns the capturing group number group:

SELECT regexp_extract('1a 2b 14m', '(\d+)([a-z]+)', 2); -- 'a'
regexp_extract_all(string, pattern) array(varchar):

Returns the substring(s) matched by the regular expression pattern in string:

SELECT regexp_extract_all('1a 2b 14m', '\d+'); -- [1, 2, 14]
regexp_extract_all(string, pattern, group) array(varchar):

Finds all occurrences of the regular expression pattern in string and returns the capturing group number group:

SELECT regexp_extract_all('1a 2b 14m', '(\d+)([a-z]+)', 2); -- ['a', 'b', 'm']
regexp_like(string, pattern) boolean

Evaluates the regular expression pattern and determines if it is contained within string.

This function is similar to the LIKE operator, except that the pattern only needs to be contained within string, rather than needing to match all of string. In other words, this performs a contains operation rather than a match operation. You can match the entire string by anchoring the pattern using ^ and $:

SELECT regexp_like('1a 2b 14m', '\d+b'); -- true
regexp_replace(string, pattern) varchar

Removes every instance of the substring matched by the regular expression pattern from string:

SELECT regexp_replace('1a 2b 14m', '\d+[ab] '); -- '14m'
regexp_replace(string, pattern, replacement) varchar

Replaces every instance of the substring matched by the regular expression pattern in string with replacement. Capturing groups can be referenced in replacement using $g for a numbered group or ${name} for a named group. A dollar sign ($) may be included in the replacement by escaping it with a backslash (\$):

SELECT regexp_replace('1a 2b 14m', '(\d+)([ab]) ', '3c$2 '); -- '3ca 3cb 14m'