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- Attribute value skew
- Tuple placement skew
- Redistribution skew (caused by bad partitioning)
- Execution skew (causes uneven bad work distribution)
Selectivity skew (in which all tuples are from P0 and none from P1)
- Join Product skew
* Some join attributes are more common in both relations
eg. For an Equi-join on attribute A in R and S
if there are 10 a's in R.A and 10 a's in S.A then
the equijoin has 10*10 a's
- Equal distribution of tuples may not be enough
DBMS
1999-03-11