A system for semantic query optimization
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Extensible/rule based query rewrite optimization in Starburst
SIGMOD '92 Proceedings of the 1992 ACM SIGMOD international conference on Management of data
Optimization of real conjunctive queries
PODS '93 Proceedings of the twelfth ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Containment of conjunctive queries: beyond relations as sets
ACM Transactions on Database Systems (TODS)
Efficient optimization of a class of relational expressions
ACM Transactions on Database Systems (TODS)
SilkRoute: A framework for publishing relational data in XML
ACM Transactions on Database Systems (TODS)
NeT & CoT: translating relational schemas to XML schemas using semantic constraints
Proceedings of the eleventh international conference on Information and knowledge management
Testing containment of conjunctive queries under functional and inclusion dependencies
PODS '82 Proceedings of the 1st ACM SIGACT-SIGMOD symposium on Principles of database systems
ACM SIGMOD Record
ICDE '96 Proceedings of the Twelfth International Conference on Data Engineering
A Rule Engine for Query Transformation in Starburst and IBM DB2 C/S DBMS
ICDE '97 Proceedings of the Thirteenth International Conference on Data Engineering
Querying XML Views of Relational Data
Proceedings of the 27th International Conference on Very Large Data Bases
Physical Data Independence, Constraints, and Optimization with Universal Plans
VLDB '99 Proceedings of the 25th International Conference on Very Large Data Bases
Optimal implementation of conjunctive queries in relational data bases
STOC '77 Proceedings of the ninth annual ACM symposium on Theory of computing
Efficient XML-to-SQL query translation: where to add the intelligence?
VLDB '04 Proceedings of the Thirtieth international conference on Very large data bases - Volume 30
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Consider an XML view defined over a relational database, and a user query specified over this view. This user XML query is typically processed using the following steps: (a) our translator maps the XML query to one or more SQL queries, (b) the relational engine translates an SQL query to a relational algebra plan, (c) the relational engine executes the algebra plan and returns SQL results, and (d) our translator translates the SQL results back to XML. However, a straightforward approach produces a relational algebra plan after step (b) that is inefficient and has redundant joins. In this paper, we report on our preliminary observations with respect to how joins in such a relational algebra plan can be minimized. Our approach works on the relational algebra plan and optimizes it using novel rewrite rules that consider pairs of joins in the plan and determine whether one of them is redundant and hence can be removed. Our study shows that algebraic techniques achieve effective join minimization, and such techniques are useful and can be integrated into mainstream SQL engines.