Re: Statistics Import and Export

On Tue, 2024-09-17 at 05:02 -0400, Corey Huinker wrote:
>
> I've taken most of Jeff's work, reincorporated it into roughly the
> same patch structure as before, and am posting it now.

I have committed the import side of this patch series; that is, the
function calls that can load stats into an existing cluster without the
need to ANALYZE.

The pg_restore_*_stats() functions are designed such that pg_dump can
emit the calls. Some design choices of the functions worth noting:

(a) a variadic signature of name/value pairs rather than ordinary SQL
arguments, which makes it easier for future versions to interpret what
has been output from a previous version; and
(b) many kinds of errors are demoted to WARNINGs, to allow some
statistics to be set for an attribute even if other statistics are
malformed (also a future-proofing design); and
(c) we are considering whether to use an in-place heap update for the
relation stats, so that a large restore doesn't bloat pg_class -- I'd
like feedback on this idea

The pg_set_*_stats() functions are designed for interactive use, such
as tweaking statistics for planner testing, experimentation, or
reproducing a plan outside of a production system. The aforementioned
design choices don't make a lot of sense in this context, so that's why
the pg_set_*_stats() functions are separate from the
pg_restore_*_stats() functions. But there's a lot of overlap, so it may
be worth discussing again whether we should only have one set of
functions.

Regards,
Jeff Davis