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Unicode Oddity

Unicode Oddity. from a Unicode PeopleSoft Database. SELECT emplid, name, LENGTH(name), BLENGTH(name) FROM ps_personal_data WHERE emplid = '007’ ; EMPLID NAME LENGTH(NAME) BLENGTH(NAME) ------------- ---------- ------------ -------------

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Unicode Oddity

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  1. Unicode Oddity

  2. from a Unicode PeopleSoft Database SELECT emplid, name, LENGTH(name), BLENGTH(name) FROM ps_personal_data WHERE emplid = '007’ ; EMPLID NAME LENGTH(NAME) BLENGTH(NAME) ------------- ---------- ------------ ------------- 007 Cona¿ová,d 10 12

  3. 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

  4. 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.

  5. How does PeopleSoft create tables? CREATE TABLE fred (fred10 VARCHAR2(30) CHECK (LENGTH(fred10)<=10) ); Table created.

  6. So... • Length checking constraint on EVERY character column in the database! • >500,000 user constraints • What effect does this have on performance

  7. 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) ); Experiment 1

  8. 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; /

  9. Results of Experiment 1 • Insert 10000 rows • CPU time for recursive SQL • on my 500Mhz Laptop • No constraints: 11.08s • With constraints 13.23s

  10. 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; /

  11. Results of Experiment 2 • >99% parse time • Duration of parse CPU • Without Constraints: 41.05s • With Constraints: 156.93s

  12. 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.

  13. Unicode Oddity David Kurtz Go-Faster Consultancy Ltd. david.kurtz@go-faster.co.uk www.go-faster.co.uk

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