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.

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.

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.

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