Re: Pluggable toaster

Hi Nikita,

> Using Table AM Routine and routing AM methods calls via it is a topic for further discussion,
> if Pluggable TOAST will be committed. [...] And even then it would be an open issue.

From personal experience with the project I have serious doubts this
is going to happen. Before such invasive changes are going to be
accepted there should be a clear understanding of how exactly TOASTers
are supposed to be used. This should be part of the documentation in
the patchset. Additionally there should be an open-soruce or
source-available extension that actually demonstrates the benefits of
TOASTers with reproducible benchmarks (we didn't even get to that part
yet).

> TOAST implementation is not necessary for Table AM.

What other use cases for TOAST do you have in mind?

>> > Have I answered your question? Please don't hesitate to point to any unclear
>> > parts, I'd be glad to explain that.
>>
>> No. To be honest, it looks like you are merely discarding most/any
>> feedback the community provided so far.
>>
>> I really think that pluggable TOASTers would be a great feature.
>> However if the goal is to get it into the core I doubt that we are
>> going to make much progress with the current approach.

To clarify, the concern about "N TOASTers vs M TableAM" was expressed
by Robert Haas back in Jan 2022:

> I agree ... but I'm also worried about what happens when we have
> multiple table AMs. One can imagine a new table AM that is
> specifically optimized for TOAST which can be used with an existing
> heap table. One can imagine a new table AM for the main table that
> wants to use something different for TOAST. So, I don't think it's
> right to imagine that the choice of TOASTer depends solely on the
> column data type. I'm not really sure how this should work exactly ...
> but it needs careful thought.

This is the most important open question so far to my knowledge. It
was never addressed, it doesn't seem like there is a plan of doing so,
the suggested alternative approach was ignored, nor are there any
strong arguments that would defend this design choice and/or criticize
the alternative one (other than general words "don't worry we know
what we are doing").

This what I mean by the community feedback being discarded.

--
Best regards,
Aleksander Alekseev