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Waldyrious (talk | contribs) Disambiguated: RE2 → RE2 (software) |
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The site allowed the use of [[regular expression]]s in queries, which at the time was not offered by any other search engine for code.{{Citation needed|date=October 2009}} This makes it resemble [[grep]], but over the world's public code. The methodology employed combines a [[trigram]] [[Search engine indexing|index]] with a custom-built, [[ReDoS|denial-of-service]] resistant [[regular expression]] engine.<ref>{{cite web |url = http://swtch.com/~rsc/regexp/regexp4.html |title = Regular Expression Matching with a Trigram Index (or: How Google Code Search Worked) |author = Russ Cox |date = January 2012 }}</ref>
In March 2010, the code of [[RE2 (software)|RE2]], the regular expression engine used in Google Code Search, was made open source.<ref>[https://opensource.googleblog.com/2010/03/re2-principled-approach-to-regular.html Google Open Source Blog: RE2: a principled approach to regular expression matching]</ref>
Google Code Search supported POSIX extended regular expression syntax, excluding back-references, collating elements, and collation classes.
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