Re: Statistics Import and Export

>
>
> Comments on 0003:
>
> * If we commit 0003, is it a useful feature by itself or does it
> require that we commit some or all of 0004-0014? Which of these need to
> be in v18?
>

Useful by itself.

0004 seems needed to me, unless we're fine with ~50% bloat in pg_class on a
new-upgraded system, or we think inplace update are on their way out.

0005 is basically theoretical, it is only needed if we change the default
relpages on partitioned tables.

0006-0011 are the vacuumdb things being debated now. I've reached out to
some of the people I spoke to at PgConf.eu to get them to chime in.

0012 is now moot as a similar patch was committed Friday.

0013 is a cleanup/optimization.

0014 is the --no-data flag, which has no meaning without 0004, but 0004 in
no way requires it.

>
> * Why does binary upgrade cause statistics to be dumped? Can you just
> make pg_upgrade specify the appropriate set of flags?
>

That decision goes back a ways, I tried to dig in the archives last night
but I was getting a Server Error on postgresql.org.

Today I'm coming up with
https://www.postgresql.org/message-id/267624.1711756062%40sss.pgh.pa.us
which is actually more about whether stats import should be the default
(consensus: yesyesyes), and the binary_upgrade test may have been because
binary_upgrade shuts off data section stuff, but table stats are in the
data section. Happy to review the decision.

> * It looks like appendNamedArgument() is never called with
> positional=true?
>

That is currently the case. Currently all params are called with name/value
pairs, but in the past we had leading positionals followed by the stat-y
parameters in name-value pairs. I'll be refactoring it to remove the
positonal=T/F argument, which leaves just a list of name-type pairs, and
thus probably reduces the urge to make it an array of structs.

> * It's pretty awkward to use an array of arrays of strings when an
> array of structs might make more sense.

That pattern was introduced here:
https://www.postgresql.org/message-id/4afa70edab849ff16238d1100b6652404e9a4d9d.camel%40j-davis.com
:)

I'll be rebasing (that's done) and refactoring 0003 to get rid of the
positional column, and moving 0014 next to 0003 because they touch the same
files.