Re: [HACKERS] user-defined numeric data types triggering ERROR:unsupported type

On 03/05/2018 08:34 PM, Tom Lane wrote:
> Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>> On 03/04/2018 09:46 PM, Tom Lane wrote:
>>> Well, I think the existing bytea bug is a counterexample to that.  If
>>> someone were to repeat that mistake with, say, UUID, these tests would not
>>> catch it, because none of them would exercise UUID-vs-something-else.
>>> For that matter, your statement is false on its face, because even if
>>> somebody tried to add say uuid-versus-int8, these tests would not catch
>>> lack of support for that in convert_to_scalar unless the specific case of
>>> uuid-versus-int8 were added to the tests.
> 
>> I suspect we're simply having different expectations what the tests
>> could/should protect against - my intention was to make sure someone
>> does not break convert_to_scalar for the currently handled types.
> 
> I concur that we could use better test coverage for the existing
> code --- the coverage report is pretty bleak there.  But I think we
> could improve that just by testing with the existing operators.  I do
> not see much use in checking that unsupported cross-type cases fail
> cleanly, because there isn't a practical way to have full coverage
> for such a concern.
> 

Hmmm, OK. I'm sure we could improve the coverage of the file in general
by using existing operators, no argument here.

Obviously, that does not work for failure cases in convert_to_scalar(),
because no existing operator can exercise those. I wouldn't call those
cases 'unsupported' - they are pretty obviously supported, just meant to
handle unknown user-defined data types. Admittedly, the operators in the
tests were rather silly but I find them rather practical.

In any case, thanks for the discussion! I now understand the reasoning
why you did not commit the tests, at least.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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