Fastest way to check if a string matches a regexp in ruby?

ruby regex performance
gioele picture gioele · Aug 9, 2012 · Viewed 101.7k times · Source

What is the fastest way to check if a string matches a regular expression in Ruby?

My problem is that I have to "egrep" through a huge list of strings to find which are the ones that match a regexp that is given at runtime. I only care about whether the string matches the regexp, not where it matches, nor what the content of the matching groups is. I hope this assumption can be used to reduce the amount of time my code spend matching regexps.

I load the regexp with

pattern = Regexp.new(ptx).freeze

I have found that string =~ pattern is slightly faster than string.match(pattern).

Are there other tricks or shortcuts that can used to make this test even faster?

Answer

Wiktor Stribiżew picture Wiktor Stribiżew · Mar 16, 2017

Starting with Ruby 2.4.0, you may use RegExp#match?:

pattern.match?(string)

Regexp#match? is explicitly listed as a performance enhancement in the release notes for 2.4.0, as it avoids object allocations performed by other methods such as Regexp#match and =~:

Regexp#match?
Added Regexp#match?, which executes a regexp match without creating a back reference object and changing $~ to reduce object allocation.

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