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_levelint
 
 /* 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_levelFROM       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