On 2/27/17 10:37 AM, Tom Lane wrote:
2. Implicit user defined type casts are not applied for COALESCE operator:
That has nothing to do with whether the cast is user-defined. It has to
do with not wanting to automatically unify types across type-category
boundaries (in this case, numeric vs. composite categories). That's per
step 4 here:
https://www.postgresql.org/docs/devel/static/typeconv-union-case.html
and it's not an easy thing to get rid of because if you're considering
more than one type category then the heuristic about preferring "preferred
types" breaks down --- how do you know which category's preferred type to
prefer?
FWIW, while working on a variant type I wished there was a way to
preempt built-in type resolution when dealing with a particular type. I
was specifically interested in function calls, which IIRC is handled by
a single function and a helper. Exporting those two and providing a hook
would have done the trick in my case.
--
Jim Nasby, Data Architect, Blue Treble Consulting, Austin TX
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