array_lower() and array_upper() are returning NULL for a non-null input, the empty array, even though lower and upper bounds are known just as well as they are for any other sized array. They are behaving as if there's something unknown about the empty array that makes it hard to provide a lower bound or upper bound.
Sorry, but I still disagree. There *is* something unknown about the lower and upper bound of an empty array because there are no bounds.
I know it's possible to work around this special case, but I'm saying it's odd to have an irregularity in the interface. What justification is there for breaking the invariant length = upper-lower+1 ?
I don't see the spec defined CARDINALITY as a workaround. It defines length as the number of elements in the array. When the array is empty, that value is clearly 0. Nothing strange about it.
Yes I read the examples you gave, but you a) had to work around the nit with a
special case in your function and b) still have corner cases where one of the
invariants I named fails, namely:
test=# select array_upper(a||b, 1), array_upper(a,1)+array_length(b) from (select '{}'::int[] as a, array[1,2] as b) as x;
array_upper | ?column? -------------+----------
2 | (1 row)
OK, you got me with this corner case. But using what you described as the result int_aggregate would give you in this case (-1), you would get an even stranger answer (-1 + 2 = 1) that would still need to be worked around.
Joe
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