proposal - enhancing plpgsql's FOREACH statement for support json type

[Pavel Stehule]

Hi

now we have lot of nice json related functions and I think so can be nice
if plpgsql's statement FOREACH can directly support json type. It can save
some CPY cycles by reducing some transformations.

My idea is following -

new syntax

FOREACH targetvar IN JSON ARRAY json array expr
LOOP
  ...

and

FOREACH targetvar, keyvar IN JSON OBJECT json record expr
LOOP
  ...


What do you think about this proposal? Comments, notes?

Regards

Pavel