OPTIMIZATION OF QUERIES ON VIEWS DEFINED BY CONDITIONAL EXPRESSIONS HAVING MUTUALLY EXCLUSIVE CONDITIONS

摘要

For an information retrieval system, a query rewrite optimization method foreliminatingcondition predicates of conditional expressions defining the values of acolumn that is referencedin the predicate of an SQL query on a view. The method evaluates the query toidentify a viewand a predicate referencing a column of the view. The column has valuesselected by aconditional expression having condition predicates defining respectivemutually exclusive rangesof values. The predicate defines a first range of values. A determination ismade as to whetherone of the condition predicates defines a mutually exclusive range of valuesthat includes thefirst range of values. And, in response, the query is rewritten to eliminatethe conditionpredicates other than the one condition predicate. The predicate is thusapplied directly to thebase tables without evaluating the conditional expression.