Re: RFI: Extending the TOAST Pointer

Hi,

> I see your point, but I do think we should also think about why we do
> the change.

Personally at the moment I care only about implementing compression
dictionaries on top of this, as is discussed in the corresponding
thread [1]. I'm going to need new fields in the TOAST pointer's
including (but not necessarily limited to) dictionary id.

As I understand, Nikita is interested in implementing 64-bit TOAST
pointers [2]. I must admit I didn't follow that thread too closely but
I can imagine the needs are similar.

Last but not least I remember somebody on the mailing list suggested
adding ZSTD compression support for TOAST, besides LZ4. Assuming I
didn't dream it, the proposal was rejected due to the limited amount
of free bits in ToastCompressionId. It was argued that two possible
combinations that are left should be treated with care and ZSTD will
not bring enough value to the users compared to LZ4.

These are 3 recent cases I could recall. This being said I think our
solution should be generic enough to cover possible future cases
and/or cases unknown to us yet.

[1]: https://postgr.es/m/CAJ7c6TM7%2BsTvwREeL74Y5U91%2B5ymNobRbOmnDRfdTonq9trZyQ%40mail.gmail.com
[2]: https://commitfest.postgresql.org/43/4296/

--
Best regards,
Aleksander Alekseev