Subject: Driver Module

From: George Gelashvili <[email-masked]>
Date: Fri, 6 Jan 2017 14:07:57 -0500

Hi there,

We are working on connecting Greenplum to pgAdmin4. Currently we are
exploring how modules work in pgAdmin. In an earlier off-thread email it
was suggested we look at "the EDB PPAS" as an example of a driver class. We
are not entirely clear on what that means.

We found:
- the BaseDriver in web/pgadmin/utils/driver, documented:
https://www.pgadmin.org/docs4/1.x/code_snippets.html?highlight=driver#basedriver
- things that look EDB-related in
web/pgadmin/utils/driver/psycopg2/__init__.py

Is it a good idea to keep looking for EDB PPAS as an example of a driver?
Does anyone know exactly where it lives?

Thanks!
George & Rob

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From: Dave Page <[email-masked]>
Date: Sun, 8 Jan 2017 09:57:31 +0000

Hi

On Friday, January 6, 2017, George Gelashvili <[email-masked]>
wrote:

> - things that look EDB-related in web/pgadmin/utils/driver/
> psycopg2/__init__.py
>

I believe 99% of it is simply inherited from the base driver, and (some
of?) the rest of it is in web/pgadmin/browser/server_groups/servers/ppas.py.

Ashesh, can you help here? You know that code infinitely better than I do.

Thanks.

-- 
Dave Page
Blog: http://pgsnake.blogspot.com
Twitter: @pgsnake

EnterpriseDB UK: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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From: George Gelashvili <[email-masked]>
Date: Wed, 11 Jan 2017 11:54:15 -0500

Hi Dave,

Thanks for the pointer.
We realized that many of the changes we would need to make for supporting
Greenplum would need to go where there is pg version checking throughout
the code. This is because unlike PPAS which mostly adds additional
features, Greenplum is based on postgres 8.3.

It looks like much of the version checking logic is repeated at points
where the features are differentiated by postgres version.

It might make sense at this point to refactor the way that feature flagging
is done to be a little bit more unified between server types and postgres
versions so that we could for example have logic along the lines of:

feature_enablement = FeatureEnablement(postgres_flavor, postgres_version)

#...

if(feature_enablement.check_internal_triggers ):
  # feature call here

and then in a feature enablement class, reference the various versions and
flavors of postgres.

Any thoughts on this?

Thanks,
Tira and George

On Sun, Jan 8, 2017 at 4:57 AM, Dave Page <[email-masked]> wrote:

>> - things that look EDB-related in web/pgadmin/utils/driver/psyco
>> pg2/__init__.py
>>

---

From: Dave Page <[email-masked]>
Date: Thu, 12 Jan 2017 09:37:37 +0530

Hi

On Wed, Jan 11, 2017 at 10:24 PM, George Gelashvili
<[email-masked]> wrote:
> Greenplum would need to go where there is pg version checking throughout the
> code. This is because unlike PPAS which mostly adds additional features,
> Greenplum is based on postgres 8.3.

Isn't Heikki fixing that for your next release?

> It looks like much of the version checking logic is repeated at points where
> the features are differentiated by postgres version.
>

I worry that the list of features would end up being huge - we're not
just talking about basic things like whether DDL triggers are
supported, but the catalog schema (e.g. procpid vs. pid in
pg_stat_activity) and small things like whether a particular GUC can
be set on a tablespace.

Ultimately, you have to do a version check at some point though
(unless you're proposing to do something similar to probing the DOM in
a browser at runtime). Doesn't GP's version string contain additional
info beyond '8.3'? In pgAdmin 3 we had a EdbMinimumVersion(int major,
int minor) function in the connection class that basically did:

return isEdb && BackendMinimumVersion(x, y);

Something like that could check other elements of the GP version number.

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---

From: Robert Eckhardt <[email-masked]>
Date: Wed, 11 Jan 2017 20:24:44 -0800

On Wed, Jan 11, 2017 at 8:07 PM, Dave Page <[email-masked]> wrote:

> the

The current release is 8.2, we aren't trying to make that work with
pgAdmin4. Heikki did a yeomans work and the next release will be based on
8.3. Future releases should be more than one Postgres version at a time but
there was a lot of cleanup to do before we could start the Postgres
merging.

> where

Greenplum is about to start leveraging semantic versioning. The version
number for the next release will be 5.0.0.

---

From: George Gelashvili <[email-masked]>
Date: Thu, 12 Jan 2017 09:48:05 -0500

Hi Dave,

We looked through the places where there is existing version checking and
there isn't a ton of it. Our current plan for supporting Greenplum in
pgAdmin4 was not necessarily to support all the features of pgAdmin4, but
to at least get the core functionality working.
I'm not too concerned about there being a ton of switches, because I don't
think most features will need to be disabled. We will also likely make
changes to Greenplum to support certain features like query plans rather
than doing all the changes on the pgAdmin4 side.

What I would like to see though is version checking that happens in one
place and is not tied exclusively to either flavor or version, but to a
combination of the two. E.g. Greenplum 5.0 might support a feature that is
not supported in 8.3 postgres.

Tira & George

---

From: Dave Page <[email-masked]>
Date: Fri, 13 Jan 2017 11:18:42 +0530

Hi

On Thu, Jan 12, 2017 at 8:18 PM, George Gelashvili
<[email-masked]> wrote:
> there isn't a ton of it.

That's because we went to great lengths to minimise it in pgAdmin 4.
It's mostly confined to template selection for SQL now.

> Our current plan for supporting Greenplum in
> pgAdmin4 was not necessarily to support all the features of pgAdmin4, but to
> at least get the core functionality working.

OK. From my perspective though, I have to ensure that what we offer in
the community is a good experience. If it's not appropriate or
necessary to support a feature in GP, that's fine - but it needs to be
disabled to prevent users reporting bugs to us

> not supported in 8.3 postgres.

Can you do a rough assessment of how many 'features' we'd be likely to
need to have the PG driver advertise? That would give a better idea of
the extent of the work involved.

In principal I'm not against the idea of having a function in each
driver that allows us to check for the presence of a given feature,
including by-version as required. What I'm against is that becoming a
mess of spaghetti...