A distinctive transformation approach of NoSQL's SQL conditions based on Espresso

Recently, numerous NoSQL (Not Only SQL) data-store systems have been developed, which often involve Big Data processing. Importantly, there are no common standard APIs for accessing the different NoSQL systems. In order to solve the problem, many scholars have used different techniques to build SQL access layer for different NoSQL databases. Meanwhile another problem related to this topic needs to be studied, which is the SQL conditions (usually as where clause) transformation problem, and unfortunately, which is not specifically described in these literatures. As we all know, this is a very complicated and important problem, in some degree, which determines whether or not the SQL query capability is flexible and powerful, which also determines the practical value of the corresponding research results. This paper proposes an approach on NoSQL's SQL conditions transformation based on Espresso heuristic algorithm. The key algorithms were given in the form of pseudo program code. A typical case and its experimental results were demonstrated finally. It is essentially more efficient, can greatly reducing the amount of memory usage and computing time, which fills the gap ignored by relevant scholars in this field to make a little contribution to the further development of NoSQL technology.