Re: A Modest Upgrade Proposal

On 07/07/2016 05:14 PM, Simon Riggs wrote:

> I would much rather see more brain power put into pg_upgrade or in
> place upgrades than logical replication (as a upgrade solution).
>
>
> Why is that?

First, let me state that I don't have a problem with logical replication
as an upgrade solution. I have used one form or another many times. I
have also used pg_upgrade and will use pg_upgrade every single time I
can over replication (even pg_logical which is reasonably simple) if I
can. *KISS* is the mantra.

I certainly think logical replication has an absolute place (especially
if upgrading from something like 9.2 -> 9.5). I just don't think it is
as useful (generally) as a solid pg_upgrade or in-place upgrade solution.

We have had logical replication as a solution for over a decade. First
there was slony then londiste and then others. They all suffered from
various issues and limitations.

* Horrible overhead
* Long running transaction
* Need for lots of extra space

It is true that something like pg_logical doesn't suffer from those
three things but it does suffer from others:

* No DDL - Agreed, not "required" but certainly a very nice feature.

* Lack of simplicity

Users, like simple. It is one of the key reasons there is a migration to
the cloud, simplicity. Everything from scaling, to pricing, to
provisioning etc...

If I take a step back and say to myself, "What would *really* rock in
terms of PostgreSQL upgrades?" The answer is pretty simple:

apt-get update; apt-get upgrade;
service postgresql upgrade;

Which would pass a flag to "insert technology here" that started
PostgreSQL in a mode that told it, "Hey, you are going to need to check
a few things and probably modify a few things before you enter "ready
for transactions"".

I am fully aware that what I am saying is not easy. There are a whole
ton of issues (what if we are replicating to a slave?).

Anyway, that's why. I am by far more a consultant than an engineer now
and I can only relay what I run into when I speak either at conferences
or clients.

Sincerely,

JD

--
Command Prompt, Inc. http://the.postgres.company/
+1-503-667-4564
PostgreSQL Centered full stack support, consulting and development.
Everyone appreciates your honesty, until you are honest with them.