Re: Catching unique_violation exception on specific column/index

On Mon, Jun 11, 2018 at 01:26:16PM +0200, Thomas Kellerer wrote:
> If that functionality is an important part of your code, you should
> consider upgrading to 10 (or 9.6 if your are really conservative)
> rather sooner than later.

Oh well, fair enough. As much as I'd love to stick to the lowest
supported (and sometimes even unsupported) versions, ON CONFLICT is
indeed very handy, esp. since I have a few UPSERT's implemented the
old way already (via catching the "unique_violation" exception).

Shall I update to 9.6/10, I have a bit off-topic (to the original
subject) question: right now, when I need to get the length of an
array (never multidimensional), I do this:

coalesce(array_length(foo, 1), 0);

In 9.4+, I can call cardinality(). I'm a bit hesitant: is doing so
semantically correct, or should I still do coalesce(..., 0) in this
case? This is not about the outcome, it's whether cardinality() is
semantically correct to obtain the number of the array items, or it
was introduced for other means?

./danfe