DB2 LUW V10 introduces Index Jump Scans as a new, more efficient, index
access ... leave the session well equipped to make optimal index design choices.
Index Jump Scans and Updated Rules for Optimal DB2 LUW Index Design Scott Hayes DBI Software Minneapolis, Milwaukee, & Chicago DB2 User Groups | Platform: IBM DB2 for LUW
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Abstract Submitted to IDUG • DB2 LUW V10 introduces Index Jump Scans as a new, more efficient, index access method. This session will do a deep dive analysis of Index Jump Scans and related performance benefits. Science projects and case studies will be explored and updated index design guidelines will be offered. Consideration will be given to Index Compression benefits as well. Attendees will leave the session well equipped to make optimal index design choices. • Submitted Bullet Points are offered in the slide notes.
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Agenda • How Indexes Work • How Index Jump Scans (are supposed to) Work • Case studies on Index Design using 12M Row Table and 11 Business Queries • Monitoring Index Activity, db2batch, & Explain
• Compression Results for Storage Size and Performance • The “New Rules” of for Index Design • Summary
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B-Tree Index Structure LR
NLEVELS =3
LR LR
ROOT page Intermediate (non-leaf) pages Leaf Pages
LR PR
NLEAF = 5
Data Pages
CREATE UNIQUE INDEX EMPNOIX on EMPLOYEE (EMPNO); SELECT * FROM EMPLOYEE WHERE EMPNO = ‘000210’; LR + LR + LR to IX + (LR to Data + PR to Data) = ¼ or 25% miss ratio, or 100 – 25% = 75% Hit Ratio for the query (assumes IX pages in BP)
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B-Tree Index Structure J-LR
NLEVELS =3
ROOT page Intermediate (non-leaf) pages
Jo-LR
Jone-LR
LR PR
LR LRPR
Jones-LR
LR PR
LR PR
Leaf Pages
LR PR
NLEAF = 20
Data Pages
CREATE INDEX LASTFIRSTIX on EMPLOYEE (LASTNAME, FIRSTNME); SELECT * FROM EMPLOYEE WHERE LASTNAME = ‘Jones’ and FIRSTNME LIKE ‘B%’ order by LASTNAME, FIRSTNME; 4X LR to IX + 6X LR to Data + 5X PR to Data, 5 Phys/10 Logical = 50% Miss Ratio, or 100 – 50% Miss Ratio = 50% Hit Ratio with 1 Sort
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B-Tree Index Structure NLEVELS =3
J-LR
ROOT page Intermediate (non-leaf) pages
Jo-LR
Jone-LR
LR LR PR LR
Jones-LR
LR PR LR LR
Leaf Pages
NLEAF = 20
Data Pages
CREATE INDEX LASTFIRSTIX on EMPLOYEE (LASTNAME, FIRSTNME) CLUSTER; SELECT * FROM EMPLOYEE WHERE LASTNAME = ‘Jones’ and FIRSTNME LIKE ‘B%’ order by LASTNAME, FIRSTNME; 4X LR to IX + 6X LR to Data + 2X PR to Data, 2 Phys/10 Logical = 20% Miss Ratio, or 100 – 20% Miss Ratio = 80% Hit Ratio with 0 Sorts
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B-Tree Index Structure NLEVELS =3
ROOT page Intermediate (non-leaf) pages Leaf Pages
NLEAF = 20
LEAF PAGE SCANS ARE EXPENSIVE!!! LR PR
LR LRPR LR
LR PR LR LR
LR PR
Data Pages
CREATE INDEX LASTFIRSTIX on EMPLOYEE (LASTNAME, FIRSTNME) CLUSTER; SELECT * FROM EMPLOYEE WHERE FIRSTNME LIKE ‘B%’; (20X LR to IX + 16X PR to IX) + (8X LR to Data + 4X PR to Data), 20 Phys/28 Logical = 71% Miss Ratio, or 100 – 71% Miss Ratio = 29% Hit Ratio
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High Cost of Leaf Page Scans Illustrated…
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INDEX JUMP SCANS NLEVELS =3
ROOT page Intermediate (non-leaf) pages Leaf Pages
NLEAF = 20
JUMP SCANS SKIP OVER PAGES LR PR
LR LRPR LR
LR PR LR LR
LR PR
Data Pages
CREATE INDEX FULLNAME on EMPLOYEE (LASTNAME, MIDINIT, FIRSTNME) SELECT * FROM EMPLOYEE WHERE LASTNAME = ‘BECK’ and FIRSTNME = ‘BETTY’ (No predicate on MIDINIT)
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I love science projects!
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Performance Science Project Table Statistics IDUG.WEBSITE_DATA_TB
6+ Years of Website Hit Data
ROWS / CARD
11,848,746
NPAGES (4K)
786,971 V9.7 / 788,604 V10
SIZE (MB)
3,074 (~3GB) V9.7 / 3,080 V10
LOCKSIZE
Row
COMPRESSION
No (will try YES later)
AVGROWSIZE
260
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Performance Science Project Column Statistics WEBSITE_DATA_TB COLUMN
COLCARD
% TB CARD
AVG #RIDS Per Value
AVG COL LEN
NUM NULLS
ACTIONVERB
36
0
329,131
8
0
AUTHID
752
0
15,756
7
0
BYTESXFERD
188,417
1
62
9
2,956
CLIENTTYPE
4,481
0
2,644
98
2,077
DOMAINNAME
192,512
1
61
29
0
HITTIMESTAMP
7,066,789
59
1
10
0
IPADDR
16,000
0
740
11
0
PROTOCOL
57
0
207,872
13
5
REFERURL
17,665
0
670
28
5
TARGETFILE
143,865
1
82
31
0
WEBSTATUS
633
0
18,718
6
5
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Interesting Values (High and Low Cards) TargetFile DomainName • /blog/rss/db2_performa nce_rss2.xml 1,129,163 hits, 9% • /blog/rss/db2nightshow _rss2.xml 446,984 hits, 3% • /db2nightshow/200910 22DB2Night04.wmv 6,743 hits,
