Google Code Search: Difference between revisions

Revision as of 02:16, 21 September 2019

Revision as of 23:43, 19 December 2019

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== Regular expression engine ==

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 |access-date = 2012-01-26 |archive-url = https://web.archive.org/web/20120128183712/http://swtch.com/~rsc/regexp/regexp4.html |archive-date = 2012-01-28 |url-status = live }}</ref>

In March 2010, the code of [[RE2 (software)|RE2]], the regular expression engine used in Google Code Search, was made open source.<ref>{{cite web|url=https://opensource.googleblog.com/2010/03/re2-principled-approach-to-regular.html|title=RE2: a principled approach to regular expression matching|publisher=|access-date=2016-09-24|archive-url=https://web.archive.org/web/20160927023834/https://opensource.googleblog.com/2010/03/re2-principled-approach-to-regular.html|archive-date=2016-09-27|url-status=live}}</ref>

Google Code Search supported POSIX extended regular expression syntax, excluding back-references, collating elements, and collation classes.

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== Discontinuation ==

In October 2011, Google announced that Code Search was to be shut down along with the Code Search API.<ref>{{cite web |last = Horowitz |first = Bradley |url = http://googleblog.blogspot.com/2011/10/fall-sweep.html |title = Official Blog: A fall sweep |publisher = Googleblog.blogspot.com |date = 2011-10-14 |accessdate = 2013-07-09 |archive-url = https://web.archive.org/web/20111123221541/http://googleblog.blogspot.com/2011/10/fall-sweep.html |archive-date = 2011-11-23 |url-status = live }}</ref> The service remained online until March 2013,<ref>{{cite web|url=https://stackoverflow.com/questions/7778034/replacement-for-google-code-search|title=Replacement for Google Code Search?|website=Stack Overflow|access-date=2016-07-25|archive-url=https://web.archive.org/web/20171109120559/https://stackoverflow.com/questions/7778034/replacement-for-google-code-search|archive-date=2017-11-09|url-status=live}}</ref> and it now returns a [[HTTP 404|404]].

In January 2012, [[Russ Cox]] published an overview of history and the technical aspects of the tool, and open-sourced a basic implementation of a similar functionality as a set of standalone programs that can run fast indexed regular expression searches over local code.<ref>{{github|google/codesearch}}</ref>