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PL/SQL fetches data 8x faster than SQL

PL/SQL Bulk Collect speed is amazing and many companies need to justify the expense of changing their PL/SQL code.

The best overall reference of hypercharging PL/SQL with bulk collect and forall array collections is Dr. Tim Hall (Oracle ACE of the year 2006) and his landmark book "Oracle PL/SQL Tuning: Expert Secrets for High Performance Programming".

Kent Crotty, author of Easy Oracle Application Express (HTML-DB) conducted a study to prove the speed of the PL/SQL bulk collect over vanilla SQL with cursor fetches:

DECLARE
TYPE prod_tab IS TABLE OF products%ROWTYPE;
products_tab           prod_tab := prod_tab();
start_time             number;
end_time               number;
CURSOR products_data IS SELECT * FROM products;
BEGIN
start_time := DBMS_UTILITY.get_time;
OPEN products_data;
LOOP
               products_tab.extend;
          FETCH products_data INTO products_tab(products_tab.last);
               IF products_data%NOTFOUND THEN
        products_tab.delete(products_tab.last);
                  EXIT;
          END IF;
END LOOP;
CLOSE products_data;
end_time := DBMS_UTILITY.get_time;
DBMS_OUTPUT.PUT_LINE(‘Conventional (‘||products_tab.count||’): ’||to_char(end_time-start_time));
 
Start_time := DBMS_UTILITY.get_time;
OPEN products_data;
FETCH products_data BULK COLLECT INTO products_tab;
CLOSE products_data; 
end_time := DBMS_UTILITY.get_time;
DBMS_OUTPUT.PUT_LINE(‘Bulk Collect (‘||products_tab.count||’): ’||to_char(end_time-start_time));
END;

Crotty's test shows an amazing speed improvement when compared to standard PL/SQL, with the bulk collect running 8x faster:

SQL> /
Conventional (100000): 117
Bulk Collect (100000): 14

Here are some related notes on this great technology:

 

  
 
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Note: This Oracle documentation was created as a support and Oracle training reference for use by our DBA performance tuning consulting professionals.  Feel free to ask questions on our Oracle forum.

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