Unicode Oddity

from a Unicode PeopleSoft Database

SELECT emplid, name, LENGTH(name), BLENGTH(name)FROM ps_personal_dataWHERE emplid = '007’;

EMPLID NAME LENGTH(NAME) BLENGTH(NAME)------------- ---------- ------------ -------------007 Cona¿ová,d 10 12

Insert 10 characters in 11 bytes

CREATE TABLE fred (fred10 VARCHAR2(11));Table created.

INSERT INTO fred SELECT name FROM ps_personal_data WHERE emplid = '007';

ERROR at line 1:ORA-01401: inserted value too large for column

Insert 10 characters in 12 bytes

CREATE TABLE fred (fred10 VARCHAR2(12));Table created.

INSERT INTO fred SELECT name FROM ps_personal_data WHERE emplid = '007';

1 row created.

How does PeopleSoft create tables?

CREATE TABLE fred (fred10 VARCHAR2(30) CHECK (LENGTH(fred10)<=10));Table created.

So...

• Length checking constraint on EVERY character column in the database!

• >500,000 user constraints

• What effect does this have on performance

Experiment 1

create table test_nocons(id number,field_01 varchar2(30)…,field_20 varchar2(30));

create table test_cons(id number,field_01 varchar2(30)

CHECK(LENGTH(field_01)<=30)

…,field_20 varchar2(30)

CHECK(LENGTH(field_01)<=30)

);

Populate tables, trace enabled

alter session set sql_trace = true;BEGIN FOR i IN 1..10000 LOOP INSERT INTO test_nocons VALUES

(i,RPAD(TO_CHAR(i),11,'.')

…,RPAD(TO_CHAR(i),30,'.'));

COMMIT; END LOOP;END;/

Results of Experiment 1

• Insert 10000 rows

• CPU time for recursive SQL • on my 500Mhz Laptop

– No constraints: 11.08s– With constraints 13.23s

Experiment 2

• Now deliberately generate different SQL statements, forcing parse every time.

BEGIN FOR i IN 1..1000 LOOP EXECUTE IMMEDIATE 'INSERT INTO test_nocons VALUES ('||

i||',RPAD(TO_CHAR('||i||'),11,''.''))'; END LOOP; COMMIT;END;/

Results of Experiment 2

• >99% parse time

• Duration of parse CPU– Without Constraints: 41.05s– With Constraints: 156.93s

Conclusion

• Execution of constraints adds overhead. – On my PC 15%-20% increase in CPU

consumption.

• If you have much SQL parsing this will aggravate the problem. In my case 4 times worse.

Unicode OddityDavid Kurtz

Go-Faster Consultancy Ltd.

david.kurtz@go-faster.co.uk

www.go-faster.co.uk