SIGMOD '86 Proceedings of the 1986 ACM SIGMOD international conference on Management of data
A rule-based view of query optimization
SIGMOD '87 Proceedings of the 1987 ACM SIGMOD international conference on Management of data
Queries and query processing in object-oriented database systems
ACM Transactions on Information Systems (TOIS)
Query evaluation techniques for large databases
ACM Computing Surveys (CSUR)
Optimization of multiple-relation multiple-disjunct queries
Proceedings of the seventh ACM SIGACT-SIGMOD-SIGART symposium on Principles of database systems
Query Optimization in Database Systems
ACM Computing Surveys (CSUR)
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Principles of Database and Knowledge-Base Systems: Volume II: The New Technologies
Access path selection in a relational database management system
SIGMOD '79 Proceedings of the 1979 ACM SIGMOD international conference on Management of data
Measuring the Complexity of Join Enumeration in Query Optimization
VLDB '90 Proceedings of the 16th International Conference on Very Large Data Bases
Bypassing Joins in Disjunctive Queries
VLDB '95 Proceedings of the 21th International Conference on Very Large Data Bases
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Most previous works on query optimization techniques deal with conjunctive queries only because the queries with disjunctive predicates are complex to optimize. Hence, for disjunctive queries, query optimizers based on these techniques generate plans using rather simple methods such as CNF- and DNF-based optimization. However, the plans generated by these methods perform extremely poorly for certain types of queries. The authors propose new query optimization method, union-pushdown, for disjunctive queries. This method is composed of four phases, and each phase utilizes some advantageous techniques of CNF- and DNF-based methods. They analyze the performance of the union-pushdown plan against those of conventional plans and show that union-pushdown can be applied to various disjunctive query types without performance degradation.