Abstract
Estimating selectivities remains a critical task in query processing. Optimizers rely on the accuracy of selectivities when generating execution plans and, in approximate query answering, estimated selectivities affect the quality of the result. Many systems maintain synopses, e.g., histograms, and, in addition, provide sampling facilities. In this paper, we present a novel approach to combine knowledge from synopses and sampling for the purpose of selectivity estimation for conjunctive queries. We first show how to extract information from synopses and sampling such that they are mutually consistent. In a second step, we show how to combine them and decide on an admissible selectivity estimate. We compare our approach to state-of-the-art methods and evaluate the strengths and limitations of each approach.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
