Re: Uber migrated from Postgres to MySQL

On Wed, Jul 27, 2016 at 9:48 PM, John R Pierce <pierce(at)hogranch(dot)com> wrote:
> On 7/27/2016 9:39 PM, Jeff Janes wrote:
>>
>> That depends on how how many objects there are consuming that 1 TB.
>> With millions of small objects, you will have problems. Not as many
>> in 9.5 as there were in 9.1, but still it does not scale linearly in
>> the number of objects. If you only have thousands of objects, then as
>> far as I know -k works like a charm.
>
>
> millions of tables?

Well, it was a problem at much smaller values, until we fixed many of
them. But the perversity is, if you are stuck on a version before the
fixes, the problems prevent you from getting to a version on which it
is not a problem any more.

> thats akin to having millions of classes in an object
> oriented program, seems a bit excessive.

It is not outside the bounds of reason, in a multi-tenancy situation.
Maybe you have a hundred tables and each table has two sequences and
7 indexes, on average. Or 300 tables and fewer indices apiece. But
then you have 1000 schemas each with the same, ah, schema. I've
pursued these optimizations as an intellectual exercise, but I know
others have had more concrete motivations.

Cheers,

Jeff