The
future
of
large
database
systems
lies
into
the
realm
of
distributed
computing.
The
main
reason
for
this
is
that
distributed
computing
can
be
constructed
at
low
cost
without
the
need
for
any
specialized
technology,
using
existing
sequential
computer
and
relatively
cheap
computer
networks.
The
great
commercial
success
of
database
systems
is
partly
due
to
the
development
of
sophisticated
query
optimization
technologies,
where
users
pose
queries
in
a
declarative
way
using
SQL
or
OQL
and
the
optimizer
of
the
database
system
finds
a
good
way
(i.e.,
plan)
to
execute
these
queries.
The
optimizer,
for
example,
determines
which
indices
should
be
used
to
execute
a
query
and
in
which
order
the
operations
of
a
query
(e.g.,
joins,
selects,
and
projects)
should
be
executed.
To
this
end,
the
optimizer
enumerates
alternative
plans,
estimates
the
cost
of
every
plan
using
a
cost
model,
and
chooses
the
plan
with
lowest
cost.
Selecting
the
optimal
execution
strategy
for
a
query
is
NP-hard
in
the
number
of
relations.
For
complex
queries
with
many
relations,
this
incurs
a
prohibitive
optimization
cost.
Therefore,
the
actual
objective
of
the
optimizer
is
to
find
a
strategy
close
to
optimal
and
to
avoid
bad
strategies.
The
selection
of
the
optimal
strategy
generally
requires
the
prediction
of
execution
cost
of
the
alternative
candidate
ordering
prior
to
actually
executing
the
query.
The
execution
cost
is
expressed
as
a
weighted
combination
of
I/O,
CPU,
and
communication
costs.
In
this
talk,
we
will
discuss
some
of
the
ways
in
which
queries
can
be
optimized
for
distributed
environments.
First,
the
problem
of
query
processing
and
optimization
is
briefly
discussed.
Different
kinds
of
search
spaces
and
search
strategies
are
evaluated
showing
the
advantages
and
disadvantages
of
each
strategy.
Second,
cost
models
are
discussed.
Finally,
the
talk
concludes
with
results
and
highlights
some
future
directions.
Speaker
Biography
Emad
Abuelrub
is
an
associate
professor
and
the
dean
of
the
Faculty
of
Science
and
Information
Technology
at
Zarqa
Private
University,
Jordan.
He
received
his
Bachelor
degrees
in
computer
engineering
and
computer
science
from
Oklahoma
State
University,
USA,
in
1984
and
1985,
respectively.
He
then
joined
the
Alabama
A&M
University,
USA,
where
he
obtained
his
MSc
degree
in
computer
science
in
1987.
He
completed
his
PhD
degree
in
computer
science
from
Louisiana
State
University,
USA,
in
1993.
His
areas
of
interest
include
parallel
and
distributed
systems,
interconnection
networks,
fault-tolerance
computing,
parallel
algorithms,
and
parallel
architectures.
He
is
a
member
of
the
IEEE,
ACM,
and
JEA.
|