pgsql-sql@postgresql.org

I've a stored procedure I'd like to migrate from MS SqlServer
to Postgresql 7.2.1. How can I do ?
here is the stored procedure
CREATE PROCEDURE ws_doc_tree_new
@parent_node_id int,
@label varchar(50),
@publication varchar(32)
AS

DECLARE
@doc_exists int,
@new_node_id int,
@parent_doc_id int,
@parent_node_path varchar(250),
@parent_tree_level int

/* check if label does not already exists */
SELECT
@doc_exists = count(*)
FROM
ws_doc_tree
WHERE
ws_doc_tree.parent_node_id = @parent_node_id
AND ws_doc_tree.label = @label

IF (@doc_exists > 0)
BEGIN
RAISERROR ('Could not create child node, a folder with the same name
already exists',16,1)
RETURN 0
END

SELECT
@parent_node_path = ws_doc_tree.node_path + ws_doc_tree.label + '/',
@parent_tree_level = ws_doc_tree.tree_level
FROM
ws_doc_tree
WHERE
ws_doc_tree.node_id = @parent_node_id

BEGIN TRANSACTION
SELECT @new_node_id = max(ws_doc_tree.node_id) + 1 FROM ws_doc_tree

INSERT INTO ws_doc_tree
(node_id,
label,
node_path,
parent_node_id,
tree_level,
publication,
creation_dt)
VALUES
(@new_node_id,
@label,
@parent_node_path,
@parent_node_id,
@parent_tree_level +1,
@publication,
current_timestamp) COMMIT TRANSACTION

RETURN @new_node_id