Can someone suggest where to document IS OF, and either document it's
non-standard behavior or supply patch?
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Joe Conway wrote:
> Gavin Sherry wrote:
> >
> > 8.14 <type predicate> to be exact.
> >
>
> 8.18 in SQL200x. I don't think the current implementation quite meets
> the spec however:
>
> regression=# select f2 is null, f2 is of(int) from bar;
> ?column? | ?column?
> ----------+----------
> f | t
> t | t
> (2 rows)
>
> If I read the spec correctly, the null value should return null, not 't'
> in the above.
>
> General Rules
> 1) Let V be the result of evaluating the <row value predicand>.
> 2) Let ST be the set consisting of every type that is either some
> exclusively specified type, or a subtype of some inclusively
> specified type.
> 3) Let TPR be the result of evaluating the <type predicate>.
>
> Case:
> a) If V is the null value, then TPR is Unknown.
> b) If the most specific type of V is a member of ST, then TPR is True .
> c) Otherwise, TPR is False
>
> Probably best not to document it until someone gets around to fixing it
> -- I can do it, but not for the next few weeks at least.
>
> Joe
>
>
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