Need some suggestions in writing package..

Question

Hi everyone,
I am just asking this question to know a better way than what i am doing.
I have a patient with 2 million rows in it.Is it possible to extract 2 million rows in a text file using UTL_FILE?.I need to extract each patient related data which comes from differnt tables (bigger than patient table) in a comma deleted file.For each patient id i have to query other tables and get the data related to that patient(according to the requirement).For that i need to call different functions against different tables.
Some think like this..
Create or replace procedure XXXX
cursor -----> to get the patient id's
variables ------> declare any other variables
begin
file handler for utl file to write into a file
open cursor
using bulk collect to fetch limited no of rows
For each patient id loop
data1 := function1
data2 := function2
data3 := function3
string : = data1|| data2 || data3|| ....
UTL_FILE.put_line
reset the string
end loop;
end;
My questions are:
Is it OK to call differnt functions for each patient id (2 million patients) are there? is there any better way to do this.
Please give me some suggestions if i need to change any steps that i am following to get better performance.
Thanks
Phani

Answer 1

Hello,
It would be strongly advisable to minimise your function calls here.
What I would suggest is: writing one piece of SQL to be looped through with BULK COLLECT, so these:
data1 := function1
data2 := function2
data3 := function3Will be taken care of in the main SQL. Otherwise things will be very, very slow.
Therefore, something like this:
BEGIN
DECLARE CURSOR c_all_data IS
                    SELECT -- put all your data to be retrieved in this SELECT, that will easily be the quickest and most efficient
                                 FROM tab1
                                 JOIN tab2 ON (...
v1,v2,...
BEGIN
   OPEN c_all_data;
   LOOP
       FETCH c_all_data BULK COLLECT INTO v1, v2, ....... LIMIT 1000;
       FOR i IN 1 .. v1.COUNT
       LOOP
            --write to your file
            UTL_FILE...
       END LOOP;
       EXIT WHEN c_all_data%NOTFOUND;
   END LOOP;
   CLOSE c_all_data;
END;