Join Summary
No single join algorithm is superior in some overall sense.
Which algorithm is best for a given query depends on:
- sizes of relations being joined, size of buffer pool
- any indexing on relations, whether relations are sorted
- which attributes and operations are used in the query
- number of tuples in S matching each tuple in R
- distribution of data values (uniform, skew, ...)
Choosing the "best" join algorithm is critical because the
cost difference between best and worst case can be very large.
E.g. Join[id=stude](Student,Enrolled): 3,000 ... 2,000,000
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