Re: Cause of intermittent rangetypes regression test failures

On Sun, 2011-11-13 at 15:38 -0500, Tom Lane wrote:
> If the table has been analyzed, then the
> most_common_values array for column ir will consist of 
>         {empty}
> which is entirely correct since that value accounts for 16% of the
> table.  And then, when mcv_selectivity tries to estimate the selectivity
> of the << condition, it applies range_before to the empty range along
> with the int4range(100,500) value, and range_before spits up.
> 
> I think this demonstrates that the current definition of range_before is
> broken.  It is not reasonable for it to throw an error on a perfectly
> valid input ... at least, not unless you'd like to mark it VOLATILE so
> that the planner will not risk calling it.
> 
> What shall we have it do instead?

We could have it return NULL, I suppose. I was worried that that would
lead to confusion between NULL and the empty range, but it might be
better than marking it VOLATILE.

Thoughts, other ideas?

Regards,Jeff Davis