- A logical relation can be
decomposted
into
mulitple physical relations
in
2 ways:
- Horizontal decomposition:
(sharding)
- The tuples of the logical relations are stored over multiple locations
Graphically:
- Vertical decomposition:
- The logical relation is decomposed into multiple relations (reconstructed using join operations)
Graphically:
Note:
- You need to use join operations to obtain the logical relation....
- Horizontal decomposition:
(sharding)
- Important reminder:
- Tuple storage (= partitioning) in
distributed datbases is
determined by the
site of creation
- Typically, a site will store tuples that were created locally
- In a distributed database system:
- Data distribution
is not based
on hashing
!!!
- Hashing (and range) based distribution is used in parallel data processing systems
- Data distribution
is not based
on hashing
!!!
- Tuple storage (= partitioning) in
distributed datbases is
determined by the
site of creation