摘要:
A novel method is employed for collecting optimizer statistics for optimizing database queries by gathering feedback from the query execution engine about the observed cardinality of predicates and constructing and maintaining multidimensional histograms. This makes use of the correlation between data columns without employing an inefficient data scan. The maximum entropy principle is used to approximate the true data distribution by a histogram distribution that is as “simple” as possible while being consistent with the observed predicate cardinalities. Changes in the underlying data are readily adapted to, automatically detecting and eliminating inconsistent feedback information in an efficient manner. The size of the histogram is controlled by retaining only the most “important” feedback.
摘要:
The present invention provides a method of selectivity estimation in which preprocessing steps improve the feasibility and efficiency of the estimation. The preprocessing steps are partitioning (to make iterative scaling estimation terminate in a reasonable time for even large sets of predicates), forced partitioning (to enable partitioning in case there are no “natural” partitions, by finding the subsets of predicates to create partitions that least impact the overall solution); inconsistency resolution (in order to ensure that there always is a correct and feasible solution), and implied zero elimination (to ensure convergence of the iterative scaling computation under all circumstances). All of these preprocessing steps make a maximum entropy method of selectivity estimation produce a correct cardinality model, for any kind of query with conjuncts of predicates. In addition, the preprocessing steps can also be used in conjunction with prior art methods for building a cardinality model.
摘要:
There is disclosed a data processing system implemented method, a data processing system, and an article of manufacture for directing a data processing system to maintain a database table associated with an initial maintenance scheduling interval. The data processing system implemented method includes selecting a randomizing factor, and selecting a new maintenance scheduling interval for the database table based on the initial maintenance scheduling interval and the selected randomizing factor.
摘要:
There is disclosed a data processing system implemented method, a data processing system, and an article of manufacture for directing a data processing system to maintain a database table associated with an initial maintenance scheduling interval. The data processing system implemented method includes selecting a randomizing factor, and selecting a new maintenance scheduling interval for the database table based on the initial maintenance scheduling interval and the selected randomizing factor.
摘要:
There is disclosed a data processing system implemented method, a data processing system, and an article of manufacture for directing a data processing system to maintain a database table associated with an initial maintenance scheduling interval. The data processing system implemented method includes selecting a randomizing factor, and selecting a new maintenance scheduling interval for the database table based on the initial maintenance scheduling interval and the selected randomizing factor.
摘要:
There is disclosed a data processing system implemented method, a data processing system, and an article of manufacture for directing a data processing system to maintain a database table associated with an initial maintenance scheduling interval. The data processing system implemented method includes selecting a randomizing factor, and selecting a new maintenance scheduling interval for the database table based on the initial maintenance scheduling interval and the selected randomizing factor.
摘要:
According to one embodiment of the present invention, a method for managing uncertain data is provided. The method includes specifying data uncertainty using at least one variable generation (VG) function, wherein the VG function generates pseudorandom samples of uncertain data values. A random database based on the VG function is specified. and multiple Monte Carlo instantiations of the random database are generated. Using a Monte Carlo method, a query is repeatedly executed over the multiple Monte Carlo instantiations to output a Monte Carlo method result and associated query-results. The Monte Carlo method result may then be used to estimate statistical properties of a probability distribution of the query-result.
摘要:
A method is disclosed for conducting a query to transform data in a pre-existing database, the method comprising: collecting database information from the pre-existing database, the database information including inconsistent dimensional tables and fact tables; running an entity discovery process on the inconsistent dimensional tables and the fact tables to produce entity mapping tables; using the entity mapping tables to resolve the inconsistent dimensional tables into resolved dimensional tables; and running the query on a resolved database to obtain a query result, the resolved database including the resolved dimensional table.
摘要:
Systems and methods directed toward processing optimization problems using loss functions, wherein a loss function is decomposed into at least one stratum loss function, a loss is decreased for each stratum loss function to a predefined stratum loss threshold individually using gradient descent, and the overall loss is decreased to a predefined threshold for the loss function by appropriately ordering the processing of the strata and spending appropriate processing time in each stratum. Other embodiments and aspects are also described herein.
摘要:
Systems and methods directed toward processing optimization problems using loss functions, wherein a loss function is decomposed into at least one stratum loss function, a loss is decreased for each stratum loss function to a predefined stratum loss threshold individually using gradient descent, and the overall loss is decreased to a predefined threshold for the loss function by appropriately ordering the processing of the strata and spending appropriate processing time in each stratum. Other embodiments and aspects are also described herein.