Database Reference
In-Depth Information
T
pLabel
= σ
(Prop=pLabel)
T
T
prodFeature
= σ
(Prop=prodFeature)
T
T
pProp
= σ
(Prop=pProp)
T
MR1:
(
T
pLabel
T
pProp
T
prodFeature
)
(Join
SJ
1)
Sub
Prop
Obj
Sub
Prop
Obj
Sub
Prop
Obj
Prod1
pLabel
Prod1
Prod1
pProp
Prod1
prodFeature
propX
PF1
M
Read
MR1
Prod2
pLabel
Prod2
Prod2
pProp
Prod1
prodFeature
propY
PF2
…
…
…
…
…
…
…
…
…
Map
MR1
M
Write
+
MR
Sort
+
MR
TR
Out
MR1
= (
T
pLabel
T
pProp
T
prodFeature
)
R
Write
Red
MR1
Sub1
Prop1
Obj1
Prop2
bj2
Prop3
bj3
pProp
propX
Prod1
pLabel
Prod1
prodFeature
PF1
pProp
propX
Prod1
pLabel
Prod1
prodFeature
PF2
MR2:
(
T
price
… T
product
)
(Join
SJ
2)
Prod1
pLabel
Prod1
pProp
propX
prodFeature
PF3
…
…
…
…
…
M
Read
…
MR2
Redundancy of non-MV components
Multivalued
Map
MR2
M
Write
+
MR
Sort
+
MR
TR
Out
MR2
= (
T
price
… T
product
)
R
Write
Red
MR2
Sub'1
Prop'1
…
Pro'p4
Obj'4
…
price
Offer1
product
Prod1
…
Offer2
price
product
Prod2
…
…
…
…
MR3:
SJ
1
SJ
2
(Join
J
1')
Out
MR3
= (
Out
MR2
Out
MR1
)
M
Read
MR3
Prop'1
…
…
Sub'1
Prop'4
Obj'4
Prop1
bj1
Prop4
bj4
…
…
price
product
Prod1
pLabel
Prod1
Map
MR3
Offer1
prodFeature
PF1
M
Write
+
MR
Sort
+
MR
TR
…
…
price
product
Prod1
pLabel
Prod1
Offer1
prodFeature
PF2
…
…
R
Write
Red
MR3
Offer1
price
product
Prod1
pLabel
Prod1
prodFeature
PF3
…
…
…
…
…
…
…
…
…
Redundancy of non-MV components
Multivalued
FIGURE 6.16
Star-join results
Out
MR
1
containing a multivalued attribute prodFeature and repeated values for the non-multivalued attributes, and a
ripple effect of the redundancy factor in the subsequent join result
Out
MR
3
.
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