# Basis Data Tersebar

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```					                                                           Materi VII: Distributed Query Processing

   Query Processing:

High level user query

Query
Processor

low level data manipulation
commands

   Komponen-komponen query processing:
 Query language
 Metodologi eksekusi query
 Optimasi query

   Proses seleksi alternatif:
Contoh:
SELECT ENAME
FROM EMP,ASG
WHERE EMP.ENO = ASG.ENO
AND DUR >37

Strategy 1:
 ENAME (  DUR 37  EMP. ENO  AS . ENO (EMP×ASG))
Strategy 2:                                                          Mana yang lebih baik ?

Π ENAME (EMP          ENO   (  DUR37 (ASG)))

   Masalahnya?

Strategy 2: plan 1                   Strategy 2: plan 2

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

   Pertimbangan biaya (cost)
Asumsi:
 size(EMP) = 400 dan jumlah rekordnya 20, size(ASG) = 1000 dan jumlah rekordnya 20
 tuple access cost = 1 unit; tuple transfer cost = 10 units
Strategi 2 plan 1:
 produce ASG': (10+10).tuple access cost 20
 transfer ASG' to the sites of EMP: (10+10).tuple transfer cost 200
 produce EMP': (10+10) .tuple access cost 2 40
 transfer EMP' to result site: (10+10) .tuple transfer cost 200
 Total cost 460
Strategi 2 plan 2:
 transfer EMP to site 5:400 tuple transfer cost 4,000
 transfer ASG to site 5 :1000 tuple transfer cost 10,000
 produce ASG':1000 tuple access cost 1,000
 join EMP and ASG':400 20 tuple access cost 8,000
 Total cost 23,000

   Distributed Query Processing Methodology

   Step 1: Query Decomposition
 Analisa
Contoh 1:
SELECT ENAME,RESP
FROM EMP, ASG, PROJ
WHERE EMP.ENO = ASG.ENO
AND ASG.PNO = PROJ.PNO
AND PNAME = "CAD/CAM"
AND DUR = 36
AND TITLE = "Programmer"

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

Contoh 2:
SELECT ENAME,RESP
FROM EMP, ASG, PROJ
WHERE EMP.ENO = ASG.ENO
AND PNAME = "CAD/CAM"
AND DUR = 36
AND TITLE = "Programmer"

 Penyederhanaan
SELECT TITLE
FROM EMP
WHERE EMP.ENAME = “J. Doe”
OR (EMP.TITLE = “Programmer”)
AND NOT (EMP.TITLE = “Programmer”
OR EMP.TITLE = “Elect. Eng.”)
AND NOT (EMP.TITLE = “Elect. Eng.”))

SELECT TITLE
FROM EMP
WHERE EMP.ENAME = “J. Doe”

 Restrukturisasi
Transformation Rules:

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

Contoh Restrukturisasi:
Find the names of employees other than J. Doe who worked on the CAD/CAM
project for either one or two years.
SELECT ENAME
FROM PROJ, ASG, EMP
WHERE ASG.ENO=EMP.ENO
AND ASG.PNO=PROJ.PNO
AND ENAME ≠ “J. Doe”
AND (DUR=12 OR DUR=24)

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

Hasil Restrukturisasi:

   Step 2: Data localization (fragment mana yang terlibat dan optimasi)

   Eliminasi pekerjaan yang tidak perlu : Reduksi untuk PHF

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

   Eliminasi pekerjaan yang tidak perlu : Reduksi untuk VF

   Eliminasi pekerjaan yang tidak perlu : Reduksi untuk DHF

Modul Basis Data Tersebar
Materi VII: Distributed Query Processing

   Eliminasi pekerjaan yang tidak perlu : Reduksi untuk HF

Modul Basis Data Tersebar

```
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