Best Effort Query Processing in DHT-based P2P Systems

Abstract

Structured P2P systems in the form of distributed hash tables (DHT) are a promising approach for building massively distributed data management platforms. However, for many applications the supported key lookup queries are not sufficient. Instead, techniques for managing and querying (relational) structured data are required. In this paper, we argue that in order to cope with the dynamics in large-scale P2P systems such query techniques should be work in a best effort manner. We describe such operations (namely grouping/aggregation, similarity and nearest neighbor search) and discuss appropriate query evaluation strategies.

Fault-tolerant query processing in structured P2P-systems

“…To cope with that problem, several multicast approaches (cf. [8] for an overview, additionally [6,[9][10][11][12]) try to store tuples of the same relation on neighboring peers, as shown on the right side of Fig. 2.…”

“…2.4. Content Addressable Network and a routing table example 2.2 Relational query processing in P2P systems A number of approaches, e.g., [5,6] have been proposed to evaluate complex, database-like queries on top of structured P2P systems that store large amounts of data sets. Generally the proposals consist of (1) a data-placement strategy which defines how relations are distributed over the network and (2) a query processor that copes with the highly distributed nature of P2P systems.…”

“…Without extensions, such systems are limited to operations that can be addressed with a key, e.g., exact-match queries. A number of query processors [5,6] has been proposed which allow the evaluation of complex SQL-like queries, including range queries, join, aggregation, etc. on top of DHTs.…”

Density-Based Clustering for Similarity Search in a P2P Network

“…Thus, the main challenge for that systems is to process complex queries such as similarity, approximate and range selections. This challenge was recently addressed in [9,21,28] by adding a layer on top of the existing DHT systems to process complex queries.…”

Query Processing in RDF/S-Based P2P Database Systems

“…The former suggests applying the following algebraic equivalence as long as the number of inter-peer (i.e., between different peers) joins in the equivalent query plan is less than the intra-peer one. This heuristic comes in accordance to best effort query processing strategies for P2P systems introduced in [43]. Moreover, promoting intra-peer processing exploits the benefits of query shipping as discussed in [13].…”