This article proposes an index key compression scheme based on the notion of distinction bits. It proves that the distinction bits of index keys are sufficient information to determine the sorted order of the index keys. The actual compression ratio may vary depending on the characteristics of datasets (an average of 2.76:1 compression ratio was observed in the authors’ experiments). However, the index key compression scheme leads to significant performance improvements during the reconstruction of large-scale indexes. This study’s index key compression can be effectively used for database replication and index recovery in modern main-memory database systems.

One of the core principles of the SAP HANA database system is the comprehensive support of distributed query facility. Supporting scale-out scenarios was one of the major design principles of the system from the very beginning. Within this paper, we first give an overview of the overall functionality with respect to data allocation, metadata caching and query routing. We then dive into some level of detail for specific topics and explain features and methods not common in traditional disk-based database systems. In summary, the paper provides a comprehensive overview of distributed query processing in SAP HANA database to achieve scalability to handle large databases and heterogeneous types of workloads.

Detecting performance anomalies and finding their root causes are tedious tasks requiring much manual work. Functionality enhancements in DBMS development as in most software development often introduce performance problems in addition to bugs. To detect the problems as soon as they are introduced, which often happens during the early phases of a development cycle, we adopt performance regression testing early in the process. In this paper, we describe a framework that we developed to manage performance anomalies after establishing a set of conditions for a problem to be considered an anomaly. The framework uses Statistical Process Control (SPC) charts to detect performance anomalies and differential profiling to identify their root causes. By automating the tasks within the framework we were able to remove most of the manual overhead in detecting anomalies and reduce the analysis time for identifying the root causes by about 90 percent in most cases. The tools developed and deployed based on the framework allow us continuous, automated daily monitoring of performance in addition to the usual functionality monitoring in our DBMS development.

Instruction on web programming at an advanced level in computer science has been in high demand in recent years. The topics and technologies in this area are so vast and diverse that designing and teaching a course requires vast knowledge and the ability to select coherent topics and technologies that can be presented in a semester. The students should learn enough of the underlying fundamental concepts along with the selected technologies so that they can practise in the real world setting while being able to adapt and expand beyond what was taught in class. Very few courses of this kind if any have been taught. We describe such a course, called Web Software Architecture, that we created and have taught successfully last Spring. It is a junior/senior level computer science elective course that uses Java, Servlets, JavaServer Pages, HTML, JavaScript, JDBC, and the Apache-Tomcat web server as key technologies. Our experience supports the assertion that such a web programming course has a legitimate place in a computer science curriculum.

The Java object serialization is designed generic method to handle all possible objects, and it performs a considerable amount of interpretation in determining the properties of objects before taking an appropriate action. In this paper, we present a mechanism by which the Java serialization is specialized using partial evaluation techniques to reduce the amount of interpretation that happens at run-time. Our approach specializes the serialization code using information about variables and arguments whose values or types are statically bound. To generate optimized code in a context-sensitive manner, it performs an interprocedural binding-time analysis. Performance measurements show an average 13% improvement in serialization, with some cases showing as high as an 18% improvement. Our approach is not restricted to serialization; rather we believe it gives a basis for a more general solution that is applicable to other aspects of Java applications.

By encapsulating aspects of language semantics within a set of default classes and allowing the programmer to derive new versions, object-oriented languages whose semantics can be tailored to the needs of individual programmers have been provided. The degree to which such languages are simultaneously flexible and efficient is an open question. We describe our experience with using this technique to incorporate transparent support for persistence into the Common Lisp Object System via its metaobject protocol, an open implementation based on reflection. For many aspects of our implementation the metaobject protocol was perfectly suitable. In other cases we had to choose between extending the protocol, requiring the application programmer to employ special idioms, and tolerating a large performance penalty. Based on our experience we evaluate the metaobject protocol, propose some improvements and extensions, and present performance measurements that reveal the need for improved language implementation techniques.>