zen and the art of SQL optimization

zen and the art of SQL optimization Karen Morton

Simplicity

“ Make everything as simple as possible but no simpler. ”
Albert Einstein

“ Normally, we do not so much look at things as overlook them.”
Alan Watts

simple vs simple-minded

Oracle 9.2.0.6 SELECT to_char( to_date(:B1,‘DD-MON-YYYY’)+1, ‘DD-MON-YYYY’ ) FROM dual;

What about its effect?

32.9% % of total R

1,087,770 # of executions

3,263,033 # of LIOs

v_date_str := to_char( to_date( :B1,‘DD-MON-YYYY’ ) + 1, ‘ DD-MON-YYYY’ ) ;

ETCIBMVIPNASAFBI

ETC IBM VIP NASA FBI

SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = 552888 ; VARCHAR2(15) SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = 552888 ; datatype mismatch causes FULL SCAN SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no =‘552888’;

SELECT rowid, load_no, load_status, manifest_no, manifest_date FROM cs_loads WHERE load_no = :B1 ;

Keys to Optimizing SQL

Tune the question, not the query.

What output should the query provide?

What special conditions need to be handled?

“ If you don’t know where you are going, you’ll end up somewhere else.”
Yogi Berra

Reduce. Reuse.

Decrease row source sizes quickly

Access objects once and reuse the result set

“ Not enough gets said about the importance of abandoning crap.” - Ira Glass

Practice.

Never stop learning

Stay connected

Think in sets

Test Test Test (then test again)

“ Practice, practice, practice. Until it becomes your practice.”
Unknown

Going Zen

SELECT invoice_id, distribution_line_number
FROM ap.ap_invoice_distributions_all ap2
WHERE ap2.project_id > 0
AND ap2.pa_addition_flag = 'T'
MINUS
FROM ap.ap_invoice_distributions_all ap,
pa.pa_cost_distribution_lines_all pa
WHERE ap.project_id > 0
AND ap.pa_addition_flag = 'T'
AND pa.system_reference2 IS NOT NULL
AND TO_NUMBER(pa.system_reference2) = ap.invoice_id
AND TO_NUMBER(pa.system_reference3) = ap.distribution_line_number
ORDER BY invoice_id;
Elapsed Time LIO Blocks PIO Blocks Total Rows
------------ ---------- ---------- ----------
00:00:20.09 60,941 57,116 6

FROM (SELECT invoice_id, distribution_line_number,
system_reference2, system_reference3
FROM ap.ap_invoice_distributions_all ap,
(SELECT TO_NUMBER(system_reference2) system_reference2,
TO_NUMBER(system_reference3) system_reference3
FROM pa.pa_cost_distribution_lines_all
WHERE system_reference2 IS NOT NULL)
WHERE system_reference2 (+) = ap.invoice_id
AND system_reference3 (+) = ap.distribution_line_number
AND ap.project_id > 0 AND ap.pa_addition_flag = 'T' )
WHERE system_reference2 IS NULL AND system_reference3 IS NULL
ORDER BY invoice_id;
------------ ---------- ---------- ----------
00:00:03.09 1,824 453 6

SELECT t.*
FROM RMS.tasks t, RMS.status s
WHERE t.status_id = s.id
AND (EXISTS ( SELECT null FROM RMS.tasks ta, RMS.resources r
WHERE t.id = ta.parent_task_id AND ta.project_code = :p
AND ta.task_type_code = 'A' AND ta.resource_id = r.id
AND r.reporting_id = :r )
OR (t.project_code = :p AND t.task_type_code = 'T') );
------------ ---------- ---------- ----------
00:00:09.50 287,330 992 3

SELECT t.* FROM RMS.tasks t, RMS.status s
WHERE t.status_id = s.id AND EXISTS
(SELECT null FROM RMS.tasks ta,RMS.resources r
AND r.reporting_id = :r )
UNION
SELECT t.* FROM RMS.tasks t, RMS.status s
WHERE t.status_id = s.id AND t.id IN
(SELECT t.parent_task_id FROM RMS.tasks t, RMS.status s
WHERE t.status_id = s.id AND
EXISTS (SELECT null FROM RMS.tasks ta, RMS.resources r
AND r.reporting_id = :r );
------------ ---------- ---------- ----------
00:00:00.01 128 0 3

SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq
FROM PS_JOB J
WHERE J.effdt = (SELECT MAX(effdt) FROM PS_JOB
WHERE emplid = J.emplid
AND empl_rcd = J.empl_rcd
AND effdt <= SYSDATE )
AND J. effseq = (SELECT MAX(effseq) FROM PS_JOB
WHERE emplid = J.emplid
AND empl_rcd = J.empl_rcd
AND effdt = J.effdt ) ;
------------ ---------- ---------- ----------
00:00:08.04 337,908 0 30,107

SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq
FROM
(SELECT J.emplid, J.empl_rcd, J.effdt, J.effseq, MAX(J.effdt)
OVER (PARTITION BY J.emplid, J.empl_rcd ) max_effdt,
LAST_VALUE(J.effseq) OVER (PARTITION BY J.emplid, J.empl_rcd
ORDER BY J.efdt, J.effseq ROWS BETWEEN CURRENT ROW AND
UNBOUNDED FOLLOWING ) max_effseq
FROM PS_JOB J
WHERE J.effdt <= SYSDATE ) J
WHERE J.effdt = J.max_effdt
AND J.effseq = J.max_effseq;
------------ ---------- ---------- ----------
00:00:00.44 1,009 0 30,107

SELECT utrsotp_desc
FROM utrsotp, ucbsvco
WHERE ucbsvco_sotp_code = utrsotp_code
AND ucbsvco_dispatch_date =
(SELECT MAX(ucbsvco_dispatch_date)
FROM ucbsvco
WHERE ucbsvco_cust_code = 1320908
AND ucbsvco_prem_code = '507601'
AND ucbsvco_stus_code = 'C'
AND ucbsvco_dispatch_ind IS NOT NULL)
AND ucbsvco_dispatch_ind IS NOT NULL
------------ ---------- ---------- ----------
00:00:20.16 106,693 0 1

SELECT utrsotp_desc
FROM utrsotp,
(SELECT ucbsvco_sotp_code, ucbsvco_dispatch_date,
MAX(ucbsvco_dispatch_date) OVER(PARTITION BY
ucbsvco_cust_code, ucbsvco_prem_code) max_dispatch_dt
FROM ucbsvco
WHERE ucbsvco_cust_code = 1320908
AND ucbsvco_prem_code = '507601'
AND ucbsvco_dispatch_ind IS NOT NULL) svco
WHERE svco.ucbsvco_dispatch_date = svco.max_dispatch_dt
AND svco.ucbsvco_sotp_code = utrsotp_code
------------ ---------- ---------- ----------
00:00:00.18 15 0 1

Simplicity is powerful…

… but it is neither simple nor easy to achieve.

It is obtained through the careful reduction of the nonessential.

While simplicity is the goal…

… it is possible to be “too simple.”

Your job is to find the balance most appropriate to your situation.

Thank You

http://www.method-r.com http://karenmorton.blogspot.com [email_address]

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zen and the art of SQL optimization

by Karen Morton

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