
Distributed Query Processing
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11.3.2 Query Fragmentation
In query fragmentation phase a relational algebraic query on global relations is converted into an
algebraic query expressed on physical fragments, called a fragment query, considering data distribu-
tion in the distributed database. A global relation can be reconstructed from its fragments using the
reconstruction rules of fragmentation [as described in Chapter 5, Section 5.3.2]. For horizontal frag-
mentation, the reconstruction rule is the union operation of relational algebra, and for vertical frag-
mentation the reconstruction rule is the join operation of relational algebra. Thus, ...