Inter-operation parallelism is two types:
1) pipelined Parallelism: It is an important source of economy of computation for database query processing. In pipelining output tuples of one operation A are consumed by a second operation B. Here the operation B starts even before the first operation has produced the entire set of tuples in its output.
In pipelined parallelism, the output tuples of one operation, A, acts as input to a second operation, B, even before the first operation has produced the entire set of tuples in its output.
Thus it is possible to run operations A and B simultaneously on different CPU's, so that the tuples produced by A is taken by B as input in parallel.
Advantages of Pipelined Parallelism
i) Pipelined operations are carried out in a sequence without writing any of the intermediate results to disk.
ii) Pipelined parallelism is useful with a small number of processors.
Disadvantages of Pipelined Parallelism
i) It does not scaleup well.
ii) Pipeline chain generally does not attain sufficient length to provide high degree of parallelism.
iii) Pipelining cannot use with some relational operation which produce cannot output until all inputs have been accessed. For example, set difference operation.
