This paper describes the design, implementation, and evaluation of Callas, a distributed database system that offers to unmodified, transactional ACID applications the opportunity to achieve a level of performance that can currently only be reached by rewriting all or part of the application in a BASE/NoSQL style. The key to combining performance and ease of programming is to decouple the ACID abstractionwhich Callas offers identically for all transactions-from the mechanism used to support it. MCC, the new Modular approach to Concurrency Control at the core of Callas, makes it possible to partition transactions in groups with the guarantee that, as long as the concurrency control mechanism within each group upholds a given isolation property, that property will also hold among transactions in different groups. Because of their limited and specialized scope, these groupspecific mechanisms can be customized for concurrency with unprecedented aggressiveness. In our MySQL Cluster-based prototype, Callas yields an 8.2x throughput gain for TPC-C with no programming effort.

This paper presents Tebaldi, a distributed key-value store that explores new ways to harness the performance opportunity of combining different specialized concurrency control mechanisms (CCs) within the same database. Tebaldi partitions conflicts at a fine granularity and matches them to specialized CCs within a hierarchical framework that is modular, extensible, and able to support a wide variety of concurrency control techniques, from single-version to multiversion and from lock-based to timestamp-based. When running the TPC-C benchmark, Tebaldi yields more than 20× the throughput of the basic two-phase locking protocol, and over 3.7× the throughput of Callas, a recent system that, like Tebaldi, aims to combine different CCs.

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“Pandemic social work” is a new concept put forward by academia in response to the epidemic, and it also points to a new field in which social work is emerging. Although most scholars mainly study its specific role in the current anti-epidemic, they do not define the meaning and field of this concept clearly, revealing the functional positioning of social work in the anti-epidemic in general, not only for the current global anti-epidemic Work has an adverse effect, and it is not without harm to the construction of this new field. Defining the concept and field of “Epidemic Social Work” needs to start from the nature of social work and learn from the successful experience of social work in other disaster areas. It is preliminarily delineated that epidemic social work is a branch of disaster social work. At the same time, in addition to conceptual clarification and field division, it also attempts to explore the theoretical basis and intervention mode of “Epidemic Social Work,” which is a new field of social work. The construction and current epidemic guidance are of great significance, and its value is obvious.