Re: Extended Statistics set/restore/clear functions.

>
> So, I have done more work on all that, and extracted two more pieces,
> applying them:
> - The bits for dependencies in the restore function, .
> - The pg_dump bits for dependencies and n_distinct, as of
> c32fb29e979d. It was sad here that your posted patch did not use the
> keys of statistics_format.h. A comment was also missing in
> AdjustUpgrade.pm, where the code will be able to handle the "version"
> tag included in the dumps.
>

Hooray!

> Another thing that I strongly suspect is going to break in the
> buildfarm are the cross-version upgrades, because the format of
> the pg_dependencies and pg_ndistinct is not completely portable.
>

We had a similar rocky experience with pg_restore_relation_stats(), so your
concerns are warranted.

> This is a filter similar to the "version" field, except that we would
> replace all the contents of the pg_ndistinct and pg_dependencies
> values inside single quotes, protecting the dump comparisons for the
> new and old versions. Let's see first what the buildfarm says and if
> I need to pull this switch.
>

+1

> And it means that at this point we are feature-complete for these two
> stats kinds, so there will be at least something for this release even
> if MCV and expressions don't make it. Still, the other pieces should
> be slightly easier to integrate now that the core parts have been
> added.
> --
> Michael
>

And here's a rebased set

0001 - adds a test left out of dependencies
0002 - mcv (plus pgdump)
0003 - exprs (plus pgdump)
0004 - capstone set-difference test that could not have succeeded until all
stat kinds were implemented.