Concepts, Languages and Architecturesdbbook.dia.uniroma3.it/Chap09.pdfVSR Taxonomy of the classes of schedule accepted by the methods VSR, CSR, 2PL and TS. Database Systems Chapter

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Database SystemsConcepts, Languages and Architectures

Paolo Atzeni • Stefano Ceri • Stefano Paraboschi • Riccardo Torlone© McGraw-Hill 1999

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Chapter 9

Technologyof a databaseserver

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Database SystemsChapter 9: Technology of a database server

© McGraw-Hill 1999

Architecture of the concurrency control system

Scheduler

read(X) write(Y) read(Z)

Database

XY

Z

YZ

X Z,X

Y Main memorybuffer


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S10 w0(x) r1(x) r1(z)w0(z) r2(x) r3(z) w3(z) w1(x)

S11 w0(x) w0(z) r1(x)r2(x) r1(z) w1(x) r3(z) w3(z)

t0

t2t1

t3

A schedule S10

conflict-equivalent to a serialschedule S

11


© McGraw-Hill 1999

t

Resourcerequested growing phase

shrinking phase

Representation of allocated resources for 2PL


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CSR

2PLTS

VSR

Taxonomy of the classes of schedule accepted bythe methods VSR, CSR, 2PL and TS


© McGraw-Hill 1999

t1 t2

t5

t3 t4

Conflict graph for a schedule


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DB

Tab 1 Tab 2 Tab n

Fragment 1 Fragment 2 Fragment n

Tuple 1 Tuple 2 Tuple n

Field 1 Field 2 Field n

The hierarchy of resources


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flush

Scheduler

BufferManager

File System

create, deleteextend

open, close

read,read_seq

Database Management System

write,write_seq

Database

YZ

X

Mainmemorybuffer

YX Z

fix use unfix force

Architecture of the buffer manager


© McGraw-Hill 1999

unfix

fix use unfix begin commit abort

BufferManager

flush

Database Management System

write,write_seq

read,read_seqY

Z

X

Database

Log

X ZY

fix use force (for db and log)

Mainmemorybuffer

Reliabilitycontrol system

Restartprocedure

Warmrestart

Coldrestart

Architecture of the reliability control system


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DumpCheckpointCheckpoint

t

Transaction record t1

Top ofthe log

B U U C

Description of a log


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W(X) W(Y)

W(Y)W(Y)

W(Y)

W(X)

t

t

t

(c)

(a)

(b)

Write in log

Write in database

W(X)

B(T) U(T,X,BS,AS) U(T,Y,BS,AS) C



Protocols for the joint writing of log and database


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Fail

Stop

Fail

Boot

Recovery

Normalfunctionality

End ofrecovery

Fail-stop model of the functioning of a DBMS


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fix

Buffer Manager

Recovery Manager

...........

DBMS

Query plans

Scanmgr

B+treemgr

Sortmgr

Hashmgr

use unfix

Access methods manager

Architecture of the access manager


© McGraw-Hill 1999

stack stack

tuple tuple tuple

page dictionary useful part of the pagechecksum

access method control information

file system control information

t3 t2 t1*t3*t2*t1

Organization of tuples within pages


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Sub-tree that containskeys K < K1

P0 K1 P1 PjKj KF PF. . . . . . . . . .

Sub-tree that containskeys Kj ≤ K< Kj+1

Sub-tree that containskeys K ≥ KF

Information contained in a node (page) of a B+ tree


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b. delete k2: merge

a. insert k3: split

initial situation

k1 k6

k1 k2 k4 k5

k1 k3 k6

k1 k2 k3 k4 k5

k1 k6

k3 k4 k5k1

Split and merge operations on a B+ tree structure


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Second level

Root node

First level

Pointers to data (arbitrarily organized)

Peter

Mavis Rick

Mavis Peter Rick TracyBabs David

Example of B+ tree


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k1 k6 k10

k2 k3 k4 k5 k7 k8 k9

t(k2) t(k3) t(k4) t(k5) t(k1) t(k6) t(k10) t(k7) t(k8) t(k9)

Example of a B tree


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Query

Dependencies

CatalogueLexical, syntactic and

semantic analysis

Algebraicoptimization

Cost-basedoptimization Profiles

Queryplan

Compilation of a query


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JA JA

a

a ---------------

---------------- a ---------------

a ---------------

Internal tableExternal tableexternalscan

internal scanor indexedaccess

Join technique with nested-loop


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J

deac

jj

emaa

jz

Left table Right table

J

J

hash(a) hash(a)

a

A A

Join technique with hashing


© McGraw-Hill 1999

(S T) R

R S T

(R S(R T

1 1 1 1

2 2 2 2

1 2T)

21

21S)

1 2

nested-loopR internal

nested-loopR external

merge-scan hash-join

nested-loopT internal

nested-loopT external

merge-scan hash-join

strategy 1 strategy 2 strategy 3 strategy 4

Execution options in a conjunctive query

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Concepts, Languages and Architecturesdbbook.dia.uniroma3.it/Chap09.pdfVSR Taxonomy of the classes of schedule accepted by the methods VSR, CSR, 2PL and TS. Database Systems Chapter