Re: Statistics Import and Export

On Thu, 2024-04-04 at 00:30 -0400, Corey Huinker wrote:
>
> v17
>
> 0001
> - array_in now repackages cast errors as warnings and skips the stat,
> test added
> - version parameter added, though it's mostly for future
> compatibility, tests modified
> - both functions delay object/attribute locking until absolutely
> necessary
> - general cleanup
>
> 0002
> - added version parameter to dumps
> - --schema-only will not dump stats unless in binary upgrade mode
> - stats are dumped SECTION_NONE
> - general cleanup
>
> I think that covers the outstanding issues. 

Thank you, this has improved a lot and the fundamentals are very close.

I think it could benefit from a bit more time to settle on a few
issues:

1. SECTION_NONE. Conceptually, stats are more like data, and so
intuitively I would expect this in the SECTION_DATA or
SECTION_POST_DATA. However, the two most important use cases (in my
opinion) don't involve dumping the data: pg_upgrade (data doesn't come
from the dump) and planner simulations/repros. Perhaps the section we
place it in is not a critical decision, but we will need to stick with
it for a long time, and I'm not sure that we have consensus on that
point.

2. We changed the stats import function API to be VARIADIC very
recently. After we have a bit of time to think on it, I'm not 100% sure
we will want to stick with that new API. It's not easy to document,
which is something I always like to consider.

3. The error handling also changed recently to change soft errors (i.e.
type input errors) to warnings. I like this change but I'd need a bit
more time to get comfortable with how this is done, there is not a lot
of precedent for doing this kind of thing. This is connected to the
return value, as well as the machine-readability concern that Magnus
raised.

Additionally, a lot of people are simply very busy around this time,
and may not have had a chance to opine on all the recent changes yet.

Regards,
Jeff Davis