Fragment-and-Replicate Join ô€‚„ Partitioning not possible for some join conditions ô€ƒŒ e.g., non-equijoin conditions, such as r.A > s.B. ô€‚„ For joins were partitioning is not applicable, parallelization can be accomplished by fragment and replicate technique ô€ƒŒ Depicted on next slide ô€‚„ Special case – asymmetric fragment-and-replicate: ô€ƒŒ One of the relations, say r, is partitioned; any partitioning technique can be used. ô€ƒŒ The other relation, s, is replicated across all the processors. ô€ƒŒ Processor Pi then locally computes the join of ri with all of s using any join technique. ô€‚„ General case: reduces the sizes of the relations at each processor. ô€ƒŒ r is partitioned into n partitions,r0, r1, ..., r n-1;s is partitioned into m partitions, s0, s1, ..., sm-1. ô€ƒŒ Any partitioning technique may be used. ô€ƒŒ There must be at least m * n processors. ô€ƒŒ Label the processors as ô€ƒŒ P0,0, P0,1, ..., P0,m-1, P1,0, ..., Pn-1m-1. ô€ƒŒ Pi,j computes the join of ri with sj. In ...
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