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Data Distribution (cont)

Consider table R horizontally partitioned into R1, R2, ..., Rn

Fragmentation can be done in multiple ways, but need to ensure ...

Completeness

  • decompostion is complete iff each t∈R is in some Ri
Reconstruction
  • original R can be produced by some relational operation
Disjoint
  • if item t ∈ Ri, then t ∉ Rk, k ≠ i   (assuming no replication)