Pavel Stehule <stehule(at)kix(dot)fsv(dot)cvut(dot)cz> writes:
> I expect v1 = [1,2], but v1 is null.
> What is wrong?
Postgres arrays don't work that way; you're assuming the semantics are
like C which they aren't.
You could get an approximation to what you want with array slicing, viz
v2[1:1][1:2]
but note that this doesn't decrease the dimensionality of the result.
regards, tom lane