lhm

Online MySQL schema migrations

Data & Databases

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Online MySQL schema migrations

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Nov 8–Nov 15 UTC · Direct repository links and separately labeled related project stories. Indexed through 11/15/2026, 8:01:28 AM UTC.

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HN mentions by year13 dated mentions

Observed mentions: 2011-05-05 18:33:56 UTC to 2020-03-26 22:24:24 UTC.

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Period	Start (UTC)	End (exclusive, UTC)	Mentions	Submissions	Comments
2011	2011-01-01 00:00:00 UTC	2012-01-01 00:00:00 UTC	1	1	0
2012	2012-01-01 00:00:00 UTC	2013-01-01 00:00:00 UTC	3	0	3
2013	2013-01-01 00:00:00 UTC	2014-01-01 00:00:00 UTC	2	0	2
2014	2014-01-01 00:00:00 UTC	2015-01-01 00:00:00 UTC	2	1	1
2015	2015-01-01 00:00:00 UTC	2016-01-01 00:00:00 UTC	0	0	0
2016	2016-01-01 00:00:00 UTC	2017-01-01 00:00:00 UTC	3	0	3
2017	2017-01-01 00:00:00 UTC	2018-01-01 00:00:00 UTC	1	0	1
2018	2018-01-01 00:00:00 UTC	2019-01-01 00:00:00 UTC	0	0	0
2019	2019-01-01 00:00:00 UTC	2020-01-01 00:00:00 UTC	0	0	0
2020	2020-01-01 00:00:00 UTC	2021-01-01 00:00:00 UTC	1	0	1

What Hacker News says

3 sources

33degrees·Aug 2, 2016

Apparently gh-ost won't work, but there are other tools that work fine on RDS: I've been using https://github.com/soundcloud/lhm On some fairly large tables (30 million + rows) without any problems

In Gh-ost: GitHub's online schema migration tool for MySQL

maximegarcia·Jul 26, 2016

https://github.com/soundcloud/lhm Saved my life a few time :)

In Why Uber Engineering Switched from Postgres to MySQL

holman·Mar 1, 2016

Yeah; I tried to stay away from really low-level aspects (just because they're hard to generalize across languages), and also just because the damn thing was so long already, ha. :) As far as database migrations are concerned, GitHub (and others, of course) takes the perspective of migrating before the code that uses those migrations go out. In other words, as @herge says in a sibling comment, the code that gets pushed needs to support two branches of code and two branches of data simultaneously. It's certainly some extra work (and can be pretty gnarly depending on the scope of the migration), but once you get to a certain point it's kind of the only way to do no-downtime migrations. There's many possibilities to help with the actual migration process, depending on what database you're using. With MySQL, for example, you can do something

Read the rest

like the process in lhm: https://github.com/soundcloud/lhm Zero-downtime deploys aren't super difficult in Rubyland anymore (many have written how they achieve it in Unicorn, for example), although I'm not as familiar with how other folk do it across other languages and platforms these days.

In How to Deploy Software