Re: Statistics Import and Export

>
>
> function attribute_statsitics_update() is significantly shorter. (Thank
> you for a good set of tests, by the way, which sped up the refactoring
> process.)
>

yw

> * Remind me why the new stats completely replace the new row, rather
> than updating only the statistic kinds that are specified?
>

because:
- complexity
- we would then need a mechanism to then tell it to *delete* a stakind
- we'd have to figure out how to reorder the remaining stakinds, or spend
effort finding a matching stakind in the existing row to know to replace it
- "do what analyze does" was an initial goal and as a result many test
cases directly compared pg_statistic rows from an original table to an
empty clone table to see if the "copy" had fidelity.

> * I'm not sure what the type_is_scalar() function was doing before,
> but I just removed it. If it can't find the element type, then it skips
> over the kinds that require it.
>

that may be sufficient,

> * I introduced some hard errors. These happen when it can't find the
> table, or the attribute, or doesn't have permissions. I don't see any
> reason to demote those to a WARNING. Even for the restore case,
> analagous errors happen for COPY, etc.
>

I can accept that reasoning.

> * I'm still sorting through some of the type info derivations. I
> think we need better explanations about why it's doing exactly the
> things it's doing, e.g. for tsvector and multiranges.

I don't have the specifics of each, but any such cases were derived from
similar behaviors in the custom typanalyze functions, and the lack of a
custom typanalyze function for a given type was taken as evidence that the
type was adequately handled by the default rules. I can see that this is an
argument for having a second stats-specific custom typanalyze function for
datatypes that need them, but I wasn't ready to go that far myself.