Rewriting queries using views in the presence of arithmetic comparisons
نویسندگان
چکیده
We consider the problem of answering queries using views, where queries and views are conjunctive queries with arithmetic comparisons over dense orders. Previous work only considered limited variants of this problem, without giving a complete solution. We first show that obtaining equivalent rewritings for conjunctive queries with arithmetic comparisons is decidable. Then we consider the problem of finding maximally contained rewritings (MCR) where the decidability proof does not carry over. We investigate two special cases of this problem where the query uses only semi-interval comparisons. In both cases decidability of finding MCRs depends on the query containment test. First, we address the case where the homomorphism property holds in testing query containment. In this case decidability is easy to prove but developing an efficient algorithm is not trivial. We develop such an algorithm and prove that it is sound and complete. This algorithm applies in many cases where the query uses only left (or right) semiinterval comparisons. Then we develop a new query containment test for the case where the containing query uses both left and right semi-interval comparisons but with only one left (or right) semi interval subgoal. Based on this test, we show how to produce an MCR which is a Datalog query with arithmetic comparisons. The containment test that we develop obtains a result of independent interest. It finds another special case where query containment in the presence of arithmetic comparisons can be tested in nondeterministic polynomial time.
منابع مشابه
Rewriting Queries Using Views with Access Patterns Under Integrity Constraints
We study the problem of rewriting queries using views in the presence of access patterns, integrity constraints, disjunction, and negation. We provide asymptotically optimal algorithms for finding minimal containing and maximal contained rewritings and for deciding whether an exact rewriting exists. We show that rewriting queries using views in this case reduces (a) to rewriting queries with ac...
متن کاملFinding Equivalent Rewritings in the Presence of Arithmetic Comparisons
The problem of rewriting queries using views has received significant attention because of its applications in a wide variety of datamanagement problems. For select-project-join SQL (a.k.a. conjunctive) queries and views, there are efficient algorithms in the literature, which find equivalent and maximally contained rewritings. In the presence of arithmetic comparisons (ACs) the problem becomes...
متن کاملRewriting General Conjunctive Queries Using Views
The problem of rewriting queries using views has important applications in data integration, query optimization, and physical data independence maintenance. Previous researchers have proposed rewriting algorithms for queries and views that are Datalog programs or conjunctive queries with arithmetic comparisons such as x < y and y ≥ 10. We present a method for finding rewritings of general conju...
متن کاملApproximate Rewriting of Queries Using Views
We study approximate, that is contained and containing, rewritings of queries using views. We consider conjunctive queries with arithmetic comparisons (CQACs), which capture the full expressive power of SQL select-project-join queries. For contained rewritings, we present a sound and complete algorithm for constructing, for CQAC queries and views, a maximally-contained rewriting (MCR) whose all...
متن کاملAlgorithm for Term Linearizations of Aggregate Queries with Comparisons
We consider the problem of rewriting queries based exclusively on views. Both queries and views can contain aggregate functions and include arithmetic comparisons. To study the equivalence of a query with its rewriting query, the so called ”linearizations of a query” need to be computed. To find the linearizations of a query, the linearizations of terms from the query need to be generated. We p...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Theor. Comput. Sci.
دوره 368 شماره
صفحات -
تاریخ انتشار 2006