Re: ZSTD TOAST compression, and an extensible compression method encoding

On Mon, Sep 28, 2026 at 10:39:42PM -0700, Nikhil Kumar Veldanda wrote:
> v7 attached

I was just looking at v7-0001 that wants to add the ToastCompressionId
to toast_external_data, and this feels half-baked due to the
inconsistency this brings with extsize and VARATT_EXTINFO_GET_EXTSIZE.

Couldn't we do better here by normalizing more data from the existing
fields? Another could be the is_compressed state which is guessed
from a comparison between the raw size and the compressed size,
perhaps?

Regarding v7-0002 and v7-0003, I am doubting the wisdom of tackling
the last-compression-bit issue for this release. The OID8 code has
already changed a lot of code, and maybe we should be conservative in
terms of the amount of the changes we do in this area for a single
release. By that, I mean to catch up on the refactoring pieces on
this thread once some dust has settled on HEAD and tackle this issue
around the time v21 opens up (Aka I'm preparing myself for these
dozens of agents to complain about the shape of the code already
committed, we'll see how it goes).
--
Michael