Paramveer(dot)Singh(at)trilogy(dot)com writes:
> Can someone tell me why postgres does not support deferring unique
> constraints?
Because no one's implemented it. The existing unique-check code is
associated with insertion of a new index entry, and it's nontrivial
to refactor it into a deferrable operation. There is a TODO item
for this, but don't hold your breath ...
regards, tom lane