How to extract the keys of a map ?

[Vincent Barat]

Hi !

I've a bag of map...

([k3#v13,k1#v11,k2#v12])
([k1#v12,k2#v22])
([k4#v31])

... and would like to extract all key names:

(k3)
(k1)
(k2)
(k1)
(k2)
(k4)

I cannot figure out how to do this (except by writting an UDF).

Any idea ?

Thanks a lot