Pipelining, in the processors technology, is the ability to execute an instruction
while fetching the next; in this context, we mean passing an output stream to the
next stage without intermediate steps (involving useless write and read operations)
and without waiting for the completion of any stage. This is another complementary
way to save time and better utilize processing power.
Infrastructure-Based.ETL
There are two main approaches to ETL: to resolve it implementing a set of scripts
and ad-hoc programs or to buy a commercial ETL tool that simplifies the job of
proposing a methodology, a graphical interface, and a language to solve specific
problems. In the market, many of these tools exist, with different levels in terms of
8 Adzic, Fiore, & Sisto
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performance (some of them are interpreted engines, some compiled and parallel),
completeness, usability, and, of course, different costs.
In our experience, we have analyzed these products and some of them almost seemed
to be quite adequate for our needs. Quite but not completely, some specific aspects
were not covered, tool methodology imposed some workaround, or the tool was too
complex/expensive for application, and so forth. The problem is that ETL scenarios
are so heterogeneous, so case-by-case specific, without any general rule, that it is not
possible to comprise them into one well-defined scheme.
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