Re: Multi-tenancy in Postgres

Emrul Islam wrote:
> I've just read through a paper
> here: http://www.edbt.org/Proceedings/2011-Uppsala/papers/edbt/a12-schiller.pdf
> about multi-tenancy.
>
> They used Postgres for their work and while it is academic and would
> need further work I'm just wondering if anyone in the Postgres team is
> looking at implementing some of the functionality described?

They seem fuzzy about what actual businesses who implement multi-tenant
environments, such as hosting companies, actually want and find missing
in PostgreSQL right now. They've tried to solve a problem I never would
have considered interesting in the first place.

On the "Shared Machine" side of things, we find complaints like how
individual PostgreSQL instances use too much power. See "Latch
implementation that wakes on postmaster death", currently under
development aimed at 9.2, aimed right at kicking that one around.

This "Shared Table" approach they spend so much time worrying about and
improving? No one cares about that except companies hosting a single
application on their giant box. This idea that there are large number
of tenants running the same application, but whom need to be isolated
from one another in some way, is not the normal state of things. Yes,
it happens on the big servers at Salesforce.com who all run the same
application; that is not a common situation however.

What the hosting companies actually want from PostgreSQL is a good
implementation of "Shared Process". One database install, every tenant
gets their own schema, tables and are expected to use some resources.
You can do this right now; I believe the infrastructure at Heroku is
built that way for example. How do the ideas in this paper actually
solve the problems they're seeing with that approach? I don't know for
sure, but I don't see anything exciting there.

I makes me kind of sad when people put a lot of work into doing a good
job on a problem that doesn't really matter very much in the real world,
and that's the overwhelming feel I get from reading this paper.
Advanced schema inheritance stuff? Don't care. Providing query cost
constraint limits for individual tenants? Now that's a useful problem
to talk about, one that people deploying multi-tenant databases are
actually being killed by. And discussing aspects of that problem does
flare up among the PostgreSQL developers regularly.

--
Greg Smith 2ndQuadrant US greg(at)2ndQuadrant(dot)com Baltimore, MD
Comprehensive and Customized PostgreSQL Training Classes:
http://www.2ndquadrant.us/postgresql-training/