Substitute for this oracle query in postGre

Hi Friends,
Does anybody know the substitute of the oracle function 'connect by
prior' in postgre sql.
The query is basically being used to get a tree structure of records. The
query in oracle is :-

select pkmsgid
from mstmessage
connect by prior pkmsgid = msgparentid
start with msgparentid = 1

Kindly suggest.

regards
Kamal

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