Thanks again Harald!
I'm busy for a couple days, but I'll look at it as soon as I can. At
the very least, I'll be able to look at it on the weekend again.
I did notice what you said about the test cases and I was curious what
you would do about the cases where there's no direct equivalent in
Linq to Objects.
Patrick Earl
On Tue, Apr 5, 2011 at 3:27 PM, Harald Mueller <[email protected]> wrote:
> Hi Patrick, all,
>
> here is a version of the "pure outer join semantics" with inner join
> optimization.
> Some remarks:
>
> * I am not at all certain the "inner join intelligence" is correct. I'm very
> inclined to write a formal proof of the algorithm ... So I post this only to
> give an idea of the complexity of the code (it might increase a little, as
> right now I only check for a few special expression structures; it might also
> shrink, as one can see quite a lot of "structural code duplication" -
> however, I did not see an obvious way to reduce the code size).
>
> * I had to change the test automation (that was also one of my "psychological
> roadblocks" which took me a day to overcome): I'm quite sure that it is not
> possible to write Linq2Objects queries that are exactly equivalent to the
> "outer join semantics" also in exceptional cases. Therefore, my original
> testing strategy did no longer work. I therefore restricted the testing only
> to those cases where the query interpreted by Linq2Objects does not throw an
> exception; in such cases, the results must be identical [this is not true for
> == with nulls on both sides, as Patrick explained in his last email; there is
> no test case currently that uses this deviating semantics].
> One might argue that this is the right way to test a Linq SQL provider anyway
> - the results for "exceptional cases" should be open to a simple
> *implementation*, as Patrick more or less requested (and not a simple
> *semantics*, as I put forward).
>
> * The 342 NHib.Linq test cases are green. 74 of the 75 new test cases are
> also green; the "projection anomaly test case" has now of course been
> "ignored", as the outer join semantics does have this anomaly.
>
> * In our discussion, the ! operator (for Patrick) and equivalence rewriting
> of queries (for me) were, as I see it, an important topic. I hope to add a
> number of test cases (at least around 20) that show the behavior in such
> cases.
>
> I hope this code gives you a base to decide whether to proceed along this way.
>
> Regards
> Harald
>
>
> --
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