Re: Uber migrated from Postgres to MySQL

On Wed, Jul 27, 2016 at 10:54:25AM -0700, Marc Fournier wrote:
> http://dev.mysql.com/doc/refman/5.7/en/downgrading.html#downgrade-paths
>
> ==
>
> Unless otherwise documented, the following downgrade paths are
> supported:
>
> • Downgrading from a release series version to an older release series
> version is supported using all downgrade methods. For example, downgrading
> from 5.7.10 to 5.7.9 is supported. Skipping release series versions is also
> supported. For example, downgrading from 5.7.11 to 5.7.9 is supported.
>
> • Downgrading one release level is supported using the logical downgrade
> method. For example, downgrading from 5.7 to 5.6 is supported.
>
> • Downgrading more than one release level is supported using the logical
> downgrade method, but only if you downgrade one release level at a time.
> For example, you can downgrade from 5.7 to 5.6, and then to 5.5.
>
> ==
>
> So, downgrade minor releases can be done by just changing the binaries …
> downgrading an older ‘major release’ requires a dump/reload …
>
> Unless I’m missing something, whether on PostgreSQL or MySQL, if you want to go
> back a major release, you would need to dump./ reload that 1TB database …

What they wanted, and I think was mentioned in the document, was that
they wanted to upgrade the slaves independently, then the master. I
think MySQL supports that, Postgres doesn't.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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