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Don Burleson Blog 








PL/SQL forall operator speeds 30x faster for table inserts

Loading an Oracle table from a PL/SQL array involves expensive context switches, and the PL/SQL FORALL operator speed is amazing.

The best overall reference of hypercharging PL/SQL table insert performance with 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 forall over vanilla SQL inserts, and found that FORALL was 30x faster in his small test:

TYPE prod_tab IS TABLE OF products%ROWTYPE;
products_tab   prod_tab := prod_tab();
start_time  number;  end_time   number;
-- Populate a collection - 100000 rows
SELECT * BULK COLLECT INTO products_tab FROM products;
Start_time := DBMS_UTILITY.get_time;
FOR i in products_tab.first .. products_tab.last LOOP
 INSERT INTO products (product_id, product_name, effective_date)
   VALUES (products_tab(i).product_id, products_tab(i).product_name,
end_time := DBMS_UTILITY.get_time;
DBMS_OUTPUT.PUT_LINE(‘Conventional Insert: ’||to_char(end_time-start_time));
Start_time := DBMS_UTILITY.get_time;
FORALL i in products_tab.first .. products_tab.last
 INSERT INTO products VALUES products_tab(i);
end_time := DBMS_UTILITY.get_time;
DBMS_OUTPUT.PUT_LINE(‘Bulk Insert: ’||to_char(end_time-start_time));

Crotty notes a great speed improvement with very few code changes, from 622 seconds to only 22 seconds:

SQL> /
Conventional Insert: 686
Bulk Insert: 22

Here are my related notes on the PL/SQL FORALL operator speed:


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