Re: postgres_fdw: using TABLESAMPLE to collect remote sample

On 12/31/22 05:42, Tom Lane wrote:
> Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com> writes:
>> After thinking about it a bit more I decided to rip out the 10% sampling
>> rate inflation.
>
> +1. I'm not sure if there's anything more we need to do there, but
> that didn't seem like that was it.
>
> I notice that the committed patch still has a reference to that hack
> though:
>
> + * Ensure the sampling rate is between 0.0 and 1.0, even after the
> + * 10% adjustment above. (Clamping to 0.0 is just paranoia.)
>
> Clamping still seems like a wise idea, but the comment is just
> confusing now.
>

Yeah, I missed that reference. Will fix.

> Also, I wonder if there is any possibility of ANALYZE failing
> with
>
> ERROR: TABLESAMPLE clause can only be applied to tables and materialized views
>
> I think the patch avoids that, but only accidentally, because
> reltuples will be 0 or -1 for a view. Maybe it'd be a good
> idea to pull back relkind along with reltuples, and check
> that too?

Not sure. I guess we can rely on reltuples being 0 or -1 in such cases,
but maybe it'd be good to at least mention that in a comment? We're not
going to use other reltuples values for views etc.

regards

--
Tomas Vondra
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