Re: Pluggable storage

On Mon, Jun 26, 2017 at 10:55 PM, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com
> wrote:

> On 06/26/2017 05:18 PM, Alexander Korotkov wrote:
>
>> I see that design question for PostgreSQL pluggable storages is very hard.
>>
>
> IMHO it's mostly expected to be hard.
>
> Firstly, PostgreSQL is a mature product with many advanced features, and
> reworking a low-level feature without breaking something on top of it is
> hard by definition.
>
> Secondly, project policies and code quality requirements set the bar very
> high too, I think.

Sure.

> BTW, I think it worth analyzing existing use-cases of pluggable
>
>> storages. I think that the most famous DBMS with pluggable storage API
>> is MySQL. This why I decided to start with it. I've added
>> MySQL/MariaDB section on wiki page.
>> https://wiki.postgresql.org/wiki/Future_of_storage#MySQL.2FMariaDB
>> It appears that significant part of MySQL storage engines are misuses.
>> MySQL lacks of various features like FDWs or writable views and so on.
>> This is why developers created a lot of pluggable storages for that
>> purposes. We definitely don't want something like this in PostgreSQL now.
>> I created special resume column where I expressed whether it
>> would be nice to have something like this table engine in PostgreSQL.
>>
>
> I don't want to discourage you, but I'm not sure how valuable this is.
>
> I agree it's valuable to have a an over-view of use cases for pluggable
> storage, but I don't think we'll get that from looking at MySQL. As you
> noticed, most of the storage engines are misuses, so it's difficult to
> learn anything valuable from them. You can argue that using FDWs to
> implement alternative storage engines is a misuse too, but at least that
> gives us a valid use case (columnar storage implemented using FDW).
>
> If anything, the MySQL storage engines should serve as a cautionary tale
> how not to do things - there's also a plenty of references in the MySQL
> "Restrictions and Limitations" section of the manual:
>
> https://downloads.mysql.com/docs/mysql-reslimits-excerpt-5.7-en.pdf

Just to clarify the thing. I don't propose any adoption of MySQL pluggable
storage API to PostgreSQL or something like this. I just wrote this table
for completeness of vision. It may appear that somebody will make some
valuable notes out of it, it may appear that not. "Yes" in third column
means only that there is positive user visible effects which are *nice to
have* in PostgreSQL.

Also, I remember there was a table with comparison of different designs of
pluggable storages and their use-cases at PGCon 2017 unconference. Could
somebody reproduce it?

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company