Query rewriting is one of the initial phases of query processing. After the original query is parsed and translated into an internal representation, query rewrite transforms it to an equivalent one by carrying out a number of optimizations that are independent of the physical state of the system. Typical transformations include un-nesting of subqueries, views expansions, elimination of redundant joins and predicates and various other simplifications.
Query rewriting is one of the phases of query processing. It refers to the application of a number of transformations to the original query in order to produce an equivalent optimized one. Such transformations do not depend on the physical state of the system (such as the size of the relations, the system workload, etc). They are usually based on well-defined rules that specify how to transform a query expression into a logically equivalent one.
The goal of query rewriting is threefold:...