Dynamic query evaluation plans
SIGMOD '89 Proceedings of the 1989 ACM SIGMOD international conference on Management of data
On the propagation of errors in the size of join results
SIGMOD '91 Proceedings of the 1991 ACM SIGMOD international conference on Management of data
Probabilistic methods in query processing
Probabilistic methods in query processing
Optimization of dynamic query evaluation plans
SIGMOD '94 Proceedings of the 1994 ACM SIGMOD international conference on Management of data
Selectivity and cost estimation for joins based on random sampling
Journal of Computer and System Sciences
Efficient mid-query re-optimization of sub-optimal query execution plans
SIGMOD '98 Proceedings of the 1998 ACM SIGMOD international conference on Management of data
SIGMOD '99 Proceedings of the 1999 ACM SIGMOD international conference on Management of data
Eddies: continuously adaptive query processing
SIGMOD '00 Proceedings of the 2000 ACM SIGMOD international conference on Management of data
Least expected cost query optimization: what can we expect?
Proceedings of the twenty-first ACM SIGMOD-SIGACT-SIGART symposium on Principles of database systems
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Exploiting statistics on query expressions for optimization
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Holistic twig joins: optimal XML pattern matching
Proceedings of the 2002 ACM SIGMOD international conference on Management of data
Estimating Answer Sizes for XML Queries
EDBT '02 Proceedings of the 8th International Conference on Extending Database Technology: Advances in Database Technology
Counting Twig Matches in a Tree
Proceedings of the 17th International Conference on Data Engineering
DataGuides: Enabling Query Formulation and Optimization in Semistructured Databases
VLDB '97 Proceedings of the 23rd International Conference on Very Large Data Bases
Estimating the Selectivity of XML Path Expressions for Internet Scale Applications
Proceedings of the 27th International Conference on Very Large Data Bases
Accelerating XPath evaluation in any RDBMS
ACM Transactions on Database Systems (TODS)
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Robust query processing through progressive optimization
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
ORDPATHs: insert-friendly XML node labels
SIGMOD '04 Proceedings of the 2004 ACM SIGMOD international conference on Management of data
Exploiting Correlated Attributes in Acquisitional Query Processing
ICDE '05 Proceedings of the 21st International Conference on Data Engineering
Towards a robust query optimizer: a principled and practical approach
Proceedings of the 2005 ACM SIGMOD international conference on Management of data
MonetDB/XQuery: a fast XQuery processor powered by a relational engine
Proceedings of the 2006 ACM SIGMOD international conference on Management of data
Bloom histogram: path selectivity estimation for XML data with updates
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
Detecting attribute dependencies from query feedback
VLDB '07 Proceedings of the 33rd international conference on Very large data bases
Foundations and Trends in Databases
Database architecture evolution: mammals flourished long before dinosaurs became extinct
Proceedings of the VLDB Endowment
Let SQL drive the XQuery workhorse (XQuery join graph isolation)
Proceedings of the 13th International Conference on Extending Database Technology
A load shedding framework for XML stream joins
DEXA'10 Proceedings of the 21st international conference on Database and expert systems applications: Part I
Linked data query processing strategies
ISWC'10 Proceedings of the 9th international semantic web conference on The semantic web - Volume Part I
Mixing bottom-up and top-down XPath query evaluation
ADBIS'11 Proceedings of the 15th international conference on Advances in databases and information systems
ROS: run-time optimization of SPARQL queries
WISM'11 Proceedings of the 2011 international conference on Web information systems and mining - Volume Part II
The database architectures research group at CWI
ACM SIGMOD Record
Robust runtime optimization and skew-resistant execution of analytical SPARQL queries on pig
ISWC'12 Proceedings of the 11th international conference on The Semantic Web - Volume Part I
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Optimization of complex XQueries combining many XPath steps and joins is currently hindered by the absence of good cardinality estimation and cost models for XQuery. Additionally, the state-of-the-art of even relational query optimization still struggles to cope with cost model estimation errors that increase with plan size, as well as with the effect of correlated joins and selections. In this research, we propose to radically depart from the traditional path of separating the query compilation and query execution phases, by having the optimizer execute, materialize partial results, and use sampling based estimation techniques to observe the characteristics of intermediates. The proposed technique takes as input a Join Graph where the edges are either equi-joins or XPath steps, and the execution environment provides value- and structural-join algorithms, as well as structural and value-based indices. While run-time optimization with sampling removes many of the vulnerabilities of classical optimizers, it brings its own challenges with respect to keeping resource usage under control, both with respect to the materialization of intermediates, as well as the cost of plan exploration using sampling. Our approach deals with these issues by limiting the run-time search space to so-called "zero-investment algorithms for which sampling can be guaranteed to be strictly linear in sample size. All operators and XML value indices used by ROX for sampling have the zero-investment property. We perform extensive experimental evaluation on large XML datasets that shows that our run-time query optimizer finds good query plans in a robust fashion and has limited run-time overhead.