Re: Uber migrated from Postgres to MySQL

[Marc Fournier <marc.fournier@xxxxxxxxxxxxxxx>]

On Jul 27, 2016, at 00:15, Condor <condor@xxxxxxxxxx> wrote:

On 26-07-2016 21:04, Dorian Hoxha wrote:

Many comments: https://news.ycombinator.com/item?id=12166585
https://www.reddit.com/r/programming/comments/4uph84/why_uber_engineering_switched_from_postgres_to/
On Tue, Jul 26, 2016 at 7:39 PM, Guyren Howe <guyren@xxxxxxxxx> wrote:

Honestly, I've never heard of anyone doing that. But it sounds like
they had good reasons.
https://eng.uber.com/mysql-migration/
Thoughts?
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They are right for upgrades.
It's a hard to shutdown 1 TB database and wait couple of days pg_upgrade to finish upgrade and meanwhile database is offline.
In some distros after upgrade of PG version you don't have old binary and library, need to do full dump and restore that take time and disk space.

Not having tried to use pg_upgrade on a 1TB database, this might not apply, but pg_upgrade has a —link option that should greatly minimize the time required to upgrade, since it eliminates the duplication of files … apparently even works on Windows:

“—link … use hard links instead of copying files to the new cluster (use junction points on Windows)"

In fact, the —link option should also mean removing the requirement for ‘double the disk space’ to do the upgrade …

I don’t have a 1TB database to try it on, mind you, so your ‘wait couple of days’ might be *with* the —link option?

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Marc G Fournier                                               http://www.2ndQuadrant.com
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