Robust Runtime Optimization and Skew-Resistant Execution of Analytical SPARQL Queries on Pig [chapter]

Spyros Kotoulas, Jacopo Urbani, Peter Boncz, Peter Mika
2012 Lecture Notes in Computer Science  
We describe a system that incrementally translates SPARQL queries to Pig Latin and executes them on a Hadoop cluster. This system is designed to work efficiently on complex queries with many self-joins over huge datasets, avoiding job failures even in the case of joins with unexpected high-value skew. To be robust against cost estimation errors, our system interleaves query optimization with query execution, determining the next steps to take based on data samples and statistics gathered during
more » ... the previous step. Furthermore, we have developed a novel skew-resistant join algorithm that replicates tuples corresponding to popular keys. We evaluate the effectiveness of our approach both on a synthetic benchmark known to generate complex queries (BSBM-BI) as well as on a Yahoo! case of data analysis using RDF data crawled from the web. Our results indicate that our system is indeed capable of processing huge datasets without pre-computed statistics while exhibiting good load-balancing properties. These authors have contributed equally to this work.
doi:10.1007/978-3-642-35176-1_16 fatcat:bkrhd4o36jfnnnm7iuiebaqtm4