Re: Statistics Import and Export

Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com> writes:
> I read that discussion, and it may be ok for pg_upgrade/pg_dump usecase and
> maybe also for IMPORT foreign schema where the SQL is generated by
> PostgreSQL itself. But not for simulating statistics. In that case, if the
> function happily installs statistics cooked by the user and those aren't
> used anywhere, users may be misled by the plans that are generated
> subsequently. Thus negating the very purpose of simulating
> statistics.

I'm not sure what you think the "purpose of simulating statistics" is,
but it seems like you have an extremely narrow-minded view of it.
I think we should allow injecting any stats that won't actively crash
the backend. Such functionality could be useful for stress-testing
the planner, for example, or even just to see what it would do in
a situation that is not what you have.

Note that I don't think pg_dump or pg_upgrade need to support
injection of counterfactual statistics. But direct calls of the
stats insertion functions should be able to do so.

regards, tom lane