Research Of Query Processing In Embedded Database

Presently, a variety of mobile and smart devices have large scale of application; correspondingly, the demand of embedded database is making a significant growth. However, as an industry-standard query language of database:Structure Query Language (SQL) makes the vast number of obstacles for Chinese database users because of its unnatural and non-Chinese characteristics. Therefore, there is an urgent need to design and implement an embedded database which should be full-featured, easy to use and support the Chinese query language for Chinese database users’demand. The core technology is database query processing techniques, therefore, the research of Chinese query language processing technology in embedded database has a great theoretical and practical value.This article focuses on query language compiler, query optimization and query execution in query processing techniques of embedded database. At first, it introduces domestic and international development status of embedded database and query processing techniques, and a brief introduction to an embedded database:CeDB which is developed by our project team. It analysis and compares common Chinese word segmentation methods and algorithms; then, describes the working principle and related technologies of lexical analyzer generator tool:Flex and the parser generator tool:Bison in our embedded database query processing. The paper purpose and implement an embedded database query language:CeSQL which can support both Chinese and English query, and elaborates its architecture, design and realization of the lexical analysis module, the syntax analysis module, as well as the semantic analysis module, and the query language conversion module based on an improved Chinese segmentation algorithm. Based on depth study on the database query optimization and execution technology, we implemented query optimization module and query execution module in CeDB, elaborate on the query optimization module in the algebraic optimization, logic optimization and physical optimization technologies, and describe the final query execution process.Finally, we design two sets of test cases for CeSQL on CeDB, the first set tests CeSQL compiler, lexical analysis, syntax analysis, semantic analysis performance, the second set tests the efficiency of query optimizer and execution modules on CeDB. The experimental results indicated that CeSQL compiler can accurately identify the Chinese statement and standard SQL statement to meet the standard requirements; however, its lack of flexibility and intelligent for recognition the Chinese statement. The efficiency test results show that our query optimization and execution module certain extent and improve the efficiency of query execution in CeDB, but the design is relatively simple and there are many areas for improvement.