LIMITING SCANS OF LOOSELY ORDERED AND/OR GROUPED RELATIONS IN A DATABASE

摘要

Data within a database object are accessed based on a query with a predicate including a plurality of conditional expressions. Elements of the database object are stored among a plurality of different storage regions along with range values for element values within each storage region. Each conditional expression of the query predicate is applied to the range values for each storage region to produce evaluation results of that conditional expression for each storage region. The evaluation result of each conditional expression for a corresponding storage region is combined to produce aggregated results for each of the storage regions, where the aggregated result for a corresponding storage region indicates results of a tri-state evaluation (e.g., true/false or unknown) of the conditional expressions for that storage region. One or more corresponding individual storage regions are scanned based on the aggregated results for those storage regions when the tri-state evaluation is unknown.

主权项

1. A method of accessing data within a database object based on a query with a predicate including a plurality of conditional expressions, wherein an element of the database object is stored among a plurality of different storage regions with each storage region being associated with first and second range values indicating a value range for element values within that storage region, the method comprising:
applying each conditional expression of the query predicate to at least one of the first and second range values for each of the storage regions to produce evaluation results of that conditional expression for the storage regions; combining the evaluation result of each conditional expression for a corresponding storage region to produce aggregated results for each of the storage regions, wherein the aggregated result for a corresponding storage region indicates at least one of satisfaction of the conditional expressions for that storage region, failure to satisfy the conditional expressions for that storage region, and insufficient information to evaluate the conditional expressions for that storage region; providing information to evaluate one or more conditional expressions for a storage region in response to the aggregated result for that storage region indicating insufficient information; and scanning one or more corresponding individual storage regions based on the aggregated results for those storage regions.