Application of Filters to Multiway Joins in MapReduce

Joining multiple datasets in MapReduce may amplify the disk and network overheads because intermediate join results have to be written to the underlying distributed file system, or map output records have to be replicated multiple times. This paper proposes a method for applying filters based on the processing order of input datasets, which is appropriate for the two types of multiway joins: common attribute joins and distinct attribute joins. The number of redundant records filtered depends on the processing order. In common attribute joins, the input records do not need to be replicated, so a set of filters is created, which are applied in turn. In distinct attribute joins, the input records have to be replicated, so multiple sets of filters need to be created, which depend on the number of join attributes. The experimental results showed that our approach outperformed a cascade of two-way joins and basic multiway joins in cases where small portions of input datasets were joined

Maintaining Consistency Under Isolation Relaxation of Web Services Transactions

Abstract. For efficiently managing Web Services (WS) transactions which are executed across multiple loosely-coupled autonomous organizations, isolation is commonly relaxed. A Web services operation of a transaction releases locks on its resources once its jobs are completed without waiting for the completions of other operations. However, those early unlocked resources can be seen by other transac-tions, which can spoil data integrity and causes incorrect outcomes. Existing WS transaction standards do not consider this problem. In this paper, we propose a mechanism to ensure the consistent executions of isolation-relaxing WS transac-tions. The mechanism effectively detects inconsistent states of transactions with a notion of a completion dependency and recovers them to consistent states. We also propose a new Web services Transaction Dependency management Protocol (WTDP). WTDP helps organizations manage the WS transactions easily without data inconsistency. WTDP is designed to be compliant with a representative WS transaction standard, the Web Services Transactions specifications, for easy inte-gration into existing WS transaction systems. We prototyped a WTDP-based WS transaction management system to validate our protocol.