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Choosing Access Methods (RelOps) (cont)

Rules for choosing σ access methods:
  • σA=c(R) and R has index on A   ⇒   indexSearch[A=c](R)
  • σA=c(R) and R is hashed on A   ⇒   hashSearch[A=c](R)
  • σA=c(R) and R is sorted on A   ⇒   binarySearch[A=c](R)
  • σA ≥ c(R) and R has clustered index on A
                                ⇒   indexSearch[A=c](R) then scan
  • σA ≥ c(R) and R is hashed on A
                                ⇒   linearSearch[A>=c](R)