7. indexes

7. Indexes

Section 7 # 1

Heap files allow record retrieval:by specifying the Record IDentifier, RID, orby scanning all records sequentially.

Sometimes, retrieval of records by specifying the values in one or more fields is needed (semantic search or value-based querying), e.g.,

Find all students in the CS dept; orFind students with gpa > 3;

Indexes are auxilliary files (separate from the data files they index) that enable answering these value-based queries efficiently.

An index contains a “search key attribute”, k, and “data entries”, k*, which lead us to the records containing the search key value.

the k*s can be actual records, or pointers to the records or pointers to pointers to the records (indirect pointers).

In these notes we will always assume the second alternative (pointer to the records).

Index Classification• Primary Indexes vs. Secondary Indexes:

– If the search key is, or at least contains, the clustered primary key, then the index is called a primary index, else it is called a secondary index.

• Clustered Indexes vs. Unclustered Indexes: – If closeness of key values implies closeness of the data records containing

those key values, the index is called a clustered index, else it is an unclustered index. (recall, since physical disk storage is not completely linear, "close" means

• 1st: close on one disk track• 2nd: on differnt tracks but on the same cylinder • 3rd: on the different cylinders but on close cylinders.

– A file can be clustered on at most 1 attribute (search key) but that attribute may be composite (made up of multiple attributes).

– The cost of retrieving data records through an index varies greatly based on whether index is clustered or not!

Section 7 # 2

Index Classification continued

• If there is at least one index entry per existing attribute value, then it is called dense, else sparse or non-dense.

Ashby

Cass

Smith

Sparse Indexon

Name

Anchor records of each page

• Every sparse index must be clustered! Sparse indexes are smaller.

• We show a sparse index on the Name attribute.

• The key values (name in this example) that do occur in a sparse index are called ANCHOR values (always the first key value that occurs on a page).

• In this example the anchor names are Ashby, Cass and Smith. Basu, Bristow, Daniels, Jones and Tracy are non-anchor names.

Ashby, 25, 3000

Smith, 44, 3000

22

25

30

40

44

44

50

Data File

Dense Indexon

Age

33

Bristow, 30, 2007

Basu, 33, 4003

Cass, 50, 5004

Tracy, 44, 5004

Daniels, 22, 6003

Jones, 40, 6003

Name, age, bonus

Section 7 # 3

key

Primary Index

Example: Assume the blocking factor (bfr) is 2, which means there is room for 2 records per page. STUDENT|S#|SNAME |LCODE ||17|BAID |NY2091||25|CLAY |NJ5101||32|THAISZ|NJ5102||38|GOOD |FL6321||57|BROWN |NY2092| |83|THOM |ND3450|

Primary Index on S# |S#|pg |17| 1 |32| 2 |57| 3

PRIMARY INDEX: I(k, k*) k ordered or clustered "key" field values from an ordered or clustered field of file

with the uniqueness property (individual value occurrences are "unique" i.e., each value can occur at most once.)

k* = pointer to page (sematic pointer - namely page number) containing the first record with key value, k.

Section 7 # 4

page 1

page 2

page 3

Clustering Index

ENROLL2 |S#|C#|GRADE|17|6 | 96 ||25|6 | 76 | |32|6 | 62 | |38|6 | 98 | |32|6 | 91 | |25|7 | 68 | |32|8 | 89 | |17|9 | 95 |

|C#|pg| Dense Clustering_Index on C# |6 | 1| |7 | 3| |8 | 4| |9 | 4|

|C#|pg| Non-dense Clustering_Index on C# |6 | 1| (indexing new anchor records only) |8 | 4|

There's no more search overhead with this 2nd type of non-dense clustering index, but

How can you know which page has C#=7? (search pages sequentially starting at page=1)

How can you know which page has C#=9? (search

pages sequentially starting at page=4)

is like a primary index except that the attribute need not be a key - but the file must be clustered on the attribute, k - and the pointer for any k is the 1st page with that k-value

Section 7 # 5

page 1

page 2

page 3

page 4

Secondary Index

S#|C#|GRADE ENROLL (unclustered C#) 32|8 | 89 |25|6 | 76 |32|6 | 62 |25|8 | 86 |38|6 | 98 |32|7 | 91 |17|5 | 96 |25|7 | 68 |17|8 | 95 |

C#|pg Secondary_Index, Option1 on C# 5 | 46 | 16 | 26 | 37 | 37 | 48 | 18 | 28 | 4

Option2: Use repeating groups of pointers (requires a variable length page attribute)

|C#|page |5 | 4 |6 | 1,2,3 |7 | 3,4 |8 | 1,2,4

Option3: Use 1 index entry for each value, with1 pointer to a linked list of record pointers. (1 level of indirection)|S#|C#|GRADE ENROLL (unclustered C#)|32|8 | 89 ||25|6 | 76 ||32|6 | 62 ||25|8 | 86 ||38|6 | 98 ||32|7 | 91 ||17|5 | 96 ||25|7 | 68 ||17|8 | 95 |

|C#| page |5 | -->|4| |6 | -->|1|->|2|->|3| |7 | -->|3|->|4| |8 | -->|1|->|2|->|4|

These indexes are the same as Clustering Indexes except, - the file need not be clustered on k, - k* points to the page or record containing k - every record must be indexed (all secondary indexes are dense). Why?

Option1: If there are multiple occurences of k, use multiple index entries for that k.

Section 7 # 6

page 1

page 4

page 2

page 3

page 5

Multi-level Index (made up of an index on an index)

STUDENT|S#|SNAME |LCODE | |17|BAID |NY2091| |25|CLAY |NJ5101||32|THAISZ|NJ5102| |38|GOOD |FL6321| |57|BROWN |NY2092| |83|THOM |ND3450| |91|PARK |MN7334| |94|SIVA |OR1123|

|S#|pg| (of index file) S#-index (nondense, primary) |17| 1| |32| 2| |57| 3| |91| 4|

2nd_LEVEL (a second level, nondense index) |S#|pg| |17| 1| |57| 2|

For any index, since it is a file clustered on the key, k, it can have a primary or clustering index on it. (constituting the second level of the multilevel index).

Section 7 # 7

page 1 of STUDENT

page 4

page 1 of First Level Index

page 2

ISAM

This Index file may still be quite large, but we can apply the idea repeatedly!

K*0

K1 K*

1K 2 K*

2K m

K*m

index entry

Non-leaf (inode

Leaf

Leaf pages contain data entries, <k,k*>. Non-Leaf or Inodes contain k values only

Pages

Overflow page

Primary pages

1 index every record by <k, k*>.

Section 7 # 8

Tree-structured or Multilevel indexing techniques: ISAM: (a variation of multilevel Secondary indexing) static structure;B+ tree: dynamic structure which adjusts gracefully under insert and delete.

Example ISAM TreeBlocking factor is 2 (each node has 2 k

entries)In any internal node or inode (non-leaf) add a

ptr for key_values < first k-value

Section 7 # 9

10,10* 15,15* 20,20* 27,27* 33,33* 37,37* 40,40* 46,46* 51,51* 55,55* 63,63* 97,97*

20 33 51 63

40

Root

Insert k=23

OverflowPages

Leaf

IndexPages

Pages

Primary

23,23*48,48*

42,42*

10,10* 15,15* 20,20* 27,27* 33,33* 37,37* 40,40* 46,46* 51,51* 55,55* 63,63* 97,97*

20 33 51 63

40

Need overflow page

Insert k=48

41,41*

Need overflow page

Insert k=41Insert k=42

Need overflow page

Section 7 # 10

Deleting 42

Note that 51 appears in index levels, but not in leaf!

Deleting 51

Deleting 97

23,23*48,48*

42,42*

10,10* 15,15* 20,20* 27,27* 33,33* 37,37* 40,40* 46,46* 51,51* 55,55* 63,63* 97,97*

20 33 51 63

40

41,41*

Section 7 # 11

B+ Tree: The Most Widely Used Index

• keeps tree height-balanced. • Minimum 50% occupancy (except for root). Each

node contains m entries, where d m 2d.– d is called the degree or order of the index.

• Supports equality and range-searches efficiently.

Index Entries

Data Entries("Sequence set")

(“Direct search set or index set”)

Section 7 # 12

Example B+ Tree (d=2)

Search begins at root, key comparisons direct it to a leaf (similar to ISAM except use comparisons to keys

and take left pointer iff < lowest key).

Root

17 24 30

2* 3* 5* 7* 14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

13

Search for 5

Search for 15

Search for all data entries 24

5*

15 is not in the file!

Leaves are doubly linked forfast sequential <, , , > search

Section 7 # 13

Example B+ Tree (contd.)

Root

17 24 30

2* 3* 5* 7* 14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

13

• Search for all data entries < 23• (note, this is the reason for the double linkage).

Section 7 # 14

Inserting a Data Entry into a B+ Tree• Find correct leaf L. • Put data entry in L.

– If L has enough space, done!– Else, must split L (into L and a new node L2)

• Redistribute entries, copy up (promote) middle key.• middle value which was promoted and is now the anchor key for L2).

• This can happen recursively (e.g., if there is no space for the promoted middle value in the inode to which it is promoted)

– To split inode, redistribute entries evenly, but push up (promote) middle key.

• So promote means Copy up at leaf; Move up at inode.

• Splits “grow” tree• only a root split increases height.

– Only tree growth possible: wider or 1 level taller at top.

Section 7 # 15

Inserting 8*

Observe how minimum occupancy is guaranteed in both leaf and index pg splits.

• Note difference between copy-up (leaf) and move-up (inode)

5 is promoted to parent node.(Note that 5 iscontinues to appear in the new leaf node, L2, as its anchor value.)

s copied up and

appears once in the index. Contrast

Entry to be inserted in parent node.(Note that 17 is moved up and only

this with a leaf split.)

2* 3* 5* 7* 14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

No room for 8, so split.

5* 7* 8*2* 3*

17 24 3013 2* 3* 5* 7*24 305 13

17

No room for 5, so split and move 17 up.5

Section 7 # 16

B+ Tree Before Inserting 8*

Note height_increase, balance and occupancy maintenance.

Root

17 24 30

2* 3* 5* 7* 14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

13

2* 3*

Root

17

24 30

14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

135

7*5* 8*

After Inserting 8*

Section 7 # 17

Deleting a Data Entry from a B+ Tree

• Start at root, find leaf L where entry belongs.

• Remove the entry.

– If L is at least half-full, done!

– If L has only d-1 entries,

• Try to re-distribute, borrowing from sibling (adjacent node with same parent as L).

• If re-distribution fails, merge L and a sibling.

• Merge could propagate to root, and therefore decreasing height.

Section 7 # 18

Example Tree After Inserting 8*

• Deleting 19* is easy.• Deleting 20* is done with re-distribution of 24* (and

revision of anchor value (from 24 to 27) in inode.

2* 3*

Root17

24 30

14* 16* 19* 20* 22* 24* 27* 29* 33* 34* 38* 39*

135

7*5* 8*

Root

2* 3*

17

30

14* 16* 33* 34* 38* 39*

135

7*5* 8* 22* 24*

27

27* 29*

Then Deleting 19*, 20*

Section 7 # 19

... And Then Deleting 24*

• Must merge.

2* 3*

17

30

14* 16* 33* 34* 38* 39*

135

7*5* 8* 22* 24*

27

27* 29*

• Observe `toss’ of index entry, 27, now that inode is below min occupancy so merge it with its sibling

2* 3* 7* 14* 16* 22* 27* 29* 33* 34* 38* 39*5* 8*

Root30135 17

• and index entry, 17 can be `pulled down’ (sibling merge, followed by pull-down)

2* 3*

17

30

14* 16* 33* 34* 38* 39*

135

7*5* 8* 22*

27

27* 29*

Section 7 # 20

Multidimensional IndexMultidimensional data almost always requires multidimensional indexing for effective access. One dimensional indexes assume a single search column, attribute (search key) which can be a

composite column or key.

Data structures, that support queries into multidimensional data specifically, fall in two categories:

1. Hash-table-like (e.g., Grid files and Partitioned Hash Functions)

2. Tree-like, eg,multi-key indexes, kd-trees, quad-trees (for sets of points); R-trees (for sets of regions as well as sets of points) ), Predicate-trees (P-trees) for vertical compressed, representations of data

Section 7 # 21

Hash-like Structures for Multidimensional e.g., Data Grid Files

Partition the POINTS in the space into a grid. In each dimension "grid lines" partition space into stripes. Points that fall directly on a grid line belong to the stripe above or to the right of it. Example: 12 customer(age,salary) 2-dimensional data records.(age,salary): (24,60) (46,60) (50,80) (50,100) (50,120) (70,100) (84,140) (30,260) (26,400) (44,360) (50,280) (60,260)

If vertical grid lines are drawn at age=40, age=65, horizontal at SAL=90K, SAL=224KThe points are hashed by ranges: 40 56400K380K360K340K320K300K280K260K240K220K200K180K160K140K120K100K 80K 60K 40K 20K 0K 0 10 20 30 40 50 60 70 80 90 100 AGE

* * *** *

*

*

**

* *

Grid hash functionage sal

pointsrange range 0-39 0-89K (24,60) 40-55 0-89K (46,60) (50,80) 40-55 90-223K (50,100)

(50,120) 56-99 90-223K (70,100) (84,140) 0-39 224-400K (30,260) (26,400) 40-55 224-400K (44,360) (50,280) 56-99 224-400K (60,260)

Inserting into Grid files: If there is room, insert, else (two methods) 1. add overflow block and chain it to the primary block, or 2. reorganize the structure by adding or moving grid lines (similar to dynamic hashing)

A problem with Grid files is that the number of buckets grows exponentially with dimension and the grid may become sparse. Section 7 # 22

is a sequence of hash functions, h=(h1,...hn) such that hi produces the ith segment of bits in the hash key, that is, h(a) is the concatenation of bit subsequences, h1(a)h2(a)..hn(a).

Example: The data file is CUSTOMER(AGE,SAL) consisting again of (24,60) (46,60) (50,80) (50,100) (50,120) (70,100) (84,140) (30,260) (26,400) (44,360) (50,280) (60,260)

Use 2 hash functions and 3 bits, the 1st bit is for age with hash function, mod2(tens_digit of age) and the last 2 bits are for salary with hash function, mod4(hundreds_digit of sal)

The lookup table is: Partitioined hash functionkey points

0 0 0 (24,060) (46,060) (26,400) 0 0 1 (84,140) 0 1 0 (60,260)0 1 1 (44,360) 1 0 0 (50,080)1 0 1 (50,100) (50,120) (70,100) 1 1 0 (30,260) (50,280) 1 1 1

Hash-like Structures for Multidimensional e.g., Partitioned hash Files

Section 7 # 23

Assume several attributes representing "dimensions" of the data points (data cube tuples) - uses a multi-level index, e.g., suppose there are 2 attributes: Provides a second level of Indexes on 2nd attribute to all tuples with same 1st attribute value

Tree-like Structures for Multidimensional e.g., Multi-key Index

/|--> / |-->

Index on .--> < |--> 1st attr / \ |..

/|/ \|--> / | / | /|--> / | / |--> --> < |----> < |--> \ | \ |.. \ |\ \|--> \ | \ \| \ /|--> \ \ / |--> \ `>< |--> \ \ |.. \ \|--> \ `-> . . . indexes on

2nd attr

Take the (age, salary) points again (24,60) (24,260) (24,400) (50,80) (50,100) (50,120) (50,280) (60,100) (60,260) (84,140)

. - - - - - - - - - - -> (24,060)

/ .- - - - - - -> (24,060)

/ / .- - - -> (24,400)

___/_________/______/ .--> |_60_|_260_|_400_____| / .- - - - - - -- - - - - -> (50,080)age / ____/________________24----' .-> |_80_|_100|_120_|_280_|- - - --> (50,280)50-------' \ `- - - - - - - --> (50,120)60. _______ `- - - - - - - - - - -> (50,100)84 `-->|100|260|- - - - - - - - - - - - - --> (60,260) \ `- - - - - - - - - - - - - - - - --> (60,100) \ _____ `- >|_140_|- - - - - - - - - - - - - - --> (84,140)

Section 7 # 24

Interior nodes have (Attribute, Value, LowPointer, HighPontr) - Value is a value which splits data points - The example below will show (a, V, down, up) with pointers going down for LowPointer and up for HighPointer. (goes up on greater or equal actually). - Attributes used for different levels are different and ROTATE among the dimensions (round robin). - The leaves are blocks of records (assume data blocks hold 2 records, i.e., the blocking factor, bfr, is 2). - to search: decide along the tree until you reach a leaf (going up on greater or equal) - to insert: decide along the tree until you reach the proper leaf if there is room there, insert; else split the block and divide its contents according to the appropriate attribute (next one in the rotation). Example: (insert into kd-tree in this order using age first then salart, sal): age,sal (50,80) (84,140) (30,260) (44,360) (50,120) (70,100) (24,60) (26,400) (50,280) (46,60) (60,260) (50,100)insert the first 2 pairs (no tree yet, since just 1 leaf block): 50, 80 84, 140

Tree-like Structures for Multidimensional e.g., k dimensional (kd tree) Index

age sal 30, 260 (leaf is full so split it and divide the contents by sal=150)

30,260 sal /

{ ,150} < \ 50,80 84,140 Section 7 # 25

30,260 sal /

{ ,150} < \ 50,80 84,140

Tree-like Structures for Multidimensional e.g., k dimensional (kd tree) Index continued

age sal 44,360 (leaf is not full so insert)

30,260 44,360

sal / { ,150} <

\ 50,80 84,140

age sal 50,120 (leaf is full so split, divide contents by age=55) 30,260

44,360 sal /

{ ,150} < \ 84,140 \age / { 55, } <

\ 50,80

50,120 Section 7 # 26

Tree-like Structures for Multidimensional e.g., k dimensional (kd tree) Index continued age sal

50,120 30,260 44,360

sal / { ,150} <

\ 84,140 \age / { 55, } <

\ 50,80

50,120

age sal 70,100 (leaf is not full so insert) 30,260

44,360 sal /

{ ,150} < 84,140\ 70,100 \age / { 55, } <

\ 50,80

50,120

age sal 24,060 (leaf is full so split, divide by sal=75) 30,260

44,360 sal /

{ ,150} < 84,140\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060

Section 7 # 27

Tree-like Structures for Multidimensional e.g., k dimensional (kd tree) Index continued 30,260

44,360 sal /

{ ,150} < 84,140\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060

age sal 26,400 (leaf full split, div by age=28)

30,260 44,360 age / { 28, }< / \ / 26,400 /

sal / { ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060

age sal 50,280 (leaf full split, div by sal=300)

44,360 sal /

(300, }< age / \ { 28, }< 30,260 / \ 50,280 / 26,400 /

sal / { ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060

Section 7 # 28


sal / (300, }< age / \ { 28, }< 30,260 / \ 50,280 / 26,400 /

sal / { ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060

age sal 46,060 (leaf not full so insert)

44,360 sal /

(300, }< age / \ { 28, }< 30,260 / \ 50,280 / 26,400 /

sal / { ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060 46,060

Section 7 # 29


sal / (300, }< age / \ { 28, }< 30,260 / \ 50,280 / 26,400 /

sal / { ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060 46,060

age sal 60,260 (leaf full split by age=40)

44,360 sal /

(300, }< age / \ 30,260 { 28, }< \ age / / \ { 40, }< / 26,400 \ / 50,280

sal / 60,260{ ,150} < 84,140

\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060 46,060

Section 7 # 30

Tree-like Structures for Multidime.g., k dim (kd tree) Index continued 44,360

sal / (300, }< age / \

30,260 { 28, }< \ age / / \ { 40, }< / 26,400 \ /

50,280sal / 60,260

{ ,150} < 84,140\ 70,100 \age / { 55, } <

\ 50,080 \ 50,120

\ sal / { ,75)<

\ 24,060 46,060

age sal 50,100 (full split age=50 full again split sal=90)

44,360 sal /

(300, }< age / \ 30,260 { 28, }< \ age / / \ { 40, }< / 26,400 \ / 50,280

sal / 60,260{ ,150} < 84,140 50,120

\ 70,100 50,100

\age / sal / { 55, } < { , 90 }<

\ age / \ \ { 50, }< 50,080

\ sal / \ { ,75)<

\ 24,060 46,060 Section 7 # 31

Tree-like Structures for Multidimensional datasets e.g., Quad tree indexes - Interior nodes (Inodes) correspond to rectangulars in 2-D (more generally, they can be constructed to represent

hypercubes higher dimensional space)

- If the number of points in the rectangle fits in a block, it's a leaf, else the rectangle is treated as interior node with children corresponding to its 4 quadrants.

- to insert into the quad treee index: search to find the proper leaf; if there's room, insert; else split node into 4 quadrants, divide contents appropriately.

Example: Build the Quad-tree index as it would develop, assuming (age,sal) arrive in this order: age,sal (24,60) (46,60) (50,80) (50,100) (50,120) (70,100) (84,140) (30,260) (26,400) (44,360) (50,280) (60,260)

Insert (24,60) (46,60)

400K380K360K340K320K300K280K260K240K220K200K180K160K140K120K100K 80K 60K 40K 20K 0K 0 10 20 30 40 50 60 70 80 90 100 AGE

* *

The only leaf node is:age sal 24,06046,060

Section 7 # 32

Tree-like Structures for Multidim datasets e.g., Quad tree indexes


* * *

24,06046,060

insertage sal 50, 080 (leaf full split (e.g., at age=50 and sal=200) divide contents by quadrant

.-NW /

/---NE age,sal /{50,200} <

\ \---SW 24,060 \ 46,060 \ `SE 50,080

Section 7 # 33

Tree-like Structures for Multidim datasets e.g., Quad tree indexes


* * *

insert 50, 100 (not full insert

.-NW /

/---NE age,sal /{50,200} <

\ \---SW 24,060 \ 46,060 \ `SE 50,080 50,100

.-NW /

/---NE age,sal /{50,200} <

\ \---SW 24,060 \ 46,060 \ `SE 50,080

insert 50, 120 full split SE at 75,100

.-NW /

/---NE age,sal /{50,200} <

\ \---SW 24,060 \ 46,060 \ `SE(75,100)<

.-NW 50,100 / 50,120 /---NE / < \ \---SW 50,080 \ \ `SE

**

ETC.

Section 7 # 34

Tree-like Structures for Multidim datasets: Region tree (Rtree) indexes - inodes of an R-tree correspond to interior regions, (which can be overlapping) (usually regions are

rectangles, tho, not necessarily)

- R-tree regions have subregions that represent the contents of their children

- And the subregions need not cover the region they subdivide (but all data must be within a subregion) Example, Consider the spatial image:

Example: Consider the spatial image:

100________________________________________________________ | | | | | | | | | .---------. | | | | | | | school | | | |_________| | | | | | |---------------------------. | | road1 | .-------. | |---------------------------| |house2 | | | |r | |_______| | | .------.________ |o_|_____________________________| | |house1|________ |a_|________pipeline_____________| | |______| |d | | | |2 | | | | | | | | | | 0 `-------------------------------------------------------' 0 100

Assume a leaf can hold 6 regions (bfr=6)

and that the 6 regions or objects above are together on 1 leaf block, whose region is shown as the outer red rectangle

Thus the R-tree has a root and 1 leaf:

( (0,0), (100,90) ) (corners of outer

red region)

road1 road2 house1 school house2 pipeline

(a full leaf with 6 objects)

Section 7 # 35

Rtree indexes cont.

100________________________________________________________ | | | | | | | | | .---------. | | | | | | | school | | | |_________| | | | | |

|---------------------------. | | road1 | .-------. | |---------------------------| |house2 | | | |r | |_______| | | .------.________ |o_|_____________________________| | |house1|________ |a_|________pipeline_____________| | |______| |d | | | |2 | | | | | | | | | | 0 `-------------------------------------------------------' 0 100

(0,0), (100,90)

road1 | road2 | house1

Now suppose a local cellular phone company adds a POP as shown.

POP

Split the full leaf putting 4 objects in 1 new leaf and 3 in the other

(minimize overlap and split ~evenly)

school | house2 | pipeline (0,0), (60,50) (20,20), (100,80)

POP

Section 7 # 36

Rtree indexes cont.

100________________________________________________________ | | | | | | | | | .---------. | | | | | | | school | | | |_________| | | | | |

|---------------------------. | | road1 | .-------. | |---------------------------| |house2 | | | |r | |_______| | | .------.________ |o_|_____________________________| | |house1|________ |a_|________pipeline_____________| | |______| |d | | | |2 | | | | | | | | | | 0 `-------------------------------------------------------' 0 100

(0,0), (100,90)

road1 | road2 | house1

POP

school | house2 | pipeline

(0,0), (60,50) (20,20), (100,80)

POP

Now suppose we insert house3

house3

Since house3 is not in either region (and both have room) we must decide to expand one of them.

If we pick the green, expanding it to (0,20), (100,80) we add 1600 units2

If we pick the purple, expanding it to ((0,0), (80,50) we add 1000 units2

so to minimize we pick the purple.

(80,50)

house2 house3

Note that house2 is in both regions.

Section 7 # 37

Similar to B-tree, except - only the common parts of key values are embedded in inodes - a single bit is used to make the navigation direction decision at each level (0 for up

and 1 for down). (zero-based bit positions are used) Example: (in this example, the tree structure is being built left-to-right) Starting with an empty structure,

Binary Radix Tree Index (AKA a trie) an additional index structure (e.g., used in IBM AS/400 systems)

INSERT JAY | LA | 25 | STAR (assigned RRN=1 to it)

INSERT JON | LA | 45 | HOOD (assigned RRN=2 1st letters are teh same (J) so the common pat is embedded in the root 2nd letters: A and O, bit 3 (zero-based count) is 1st difference (and makes the decision)

0123 4567 bit positionsDBCDIC for A=1100 0001EBCDIC for O=1101 0110

1 | JAY | LA | 25 | STAR

CUSTOMER FILERRN nam loc age job

2 | JON | LA | 45 | HOODJAY 1

nam_trie_INDEX

namepart RRN

b3 J<

ON 2

Section 7 # 38

Binary Radix Tree Index (AKA a trie) cont.

INSERT JAN | RO | 93 | DOC (assigned RRN=3

0123 4567 bit positionsDBCDIC for N=1101 0101EBCDIC for Y=1110 0000

1 | JAY | LA | 25 | STAR


2 | JON | LA | 45 | HOOD

nam_trie_INDEX

JAY 1b3 J<

ON 2

N 3b2 A<

Y 1

b3

J<

ON 2

3 | JAN | RO | 93 | DOC

Section 7 # 39

Binary Radix Tree Index (AKA a trie) cont.

INSERT SUE | RO | 16 | PROG (assigned RRN=4

0123 4567 bit positionsDBCDIC for J= 1101 0001EBCDIC for Y= 1110 0010

1 | JAY | LA | 25 | STAR


2 | JON | LA | 45 | HOOD

nam_trie_INDEX

N 3b2 A<

Y 1

b3

J<

ON 2

b2

<

SUE 2

3 | JAN | RO | 93 | DOC4 | SUE | RO | 16 | PROG

Section 7 # 40

Thank you.

Section 7

7. indexes

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