Cloudera, Inc.

Databricks Inc.

Mostafa Mokhtar

Alexander Behm

Sriram Krishnamurthy

Shoumik Palkar

Disclosed herein is a method for determining whether to apply a lazy materialization technique to a query run. A data processing service receives a request to perform a query identifying a filter column and a non-filter column in a columnar database. The data processing service accesses a first task of contiguous rows in the filter column from a cloud-based object storage. The data processing service applies a filter defined by the query to the first task. The data processing service generates filter results for the first task that may include a percentage of the first task discarded and a run-time. The data processing service determines, based on the filter results for the first task, a likelihood value that indicates a likelihood of gaining a performance benefit by applying the lazy materialization technique to a second task of the query.

Adaptive approach to lazy materialization in database scans using pushed filters

The problem of distinct value estimation has many applications, but is particularly important in the field of database technology where such information is utilized by query planners to generate and optimize query plans. Introduced is a novel technique for estimating the number of distinct values in a given dataset without scanning all of the values in the dataset. In an example embodiment, the introduced technique includes gathering multiple intermediate probabilistic estimates based on varying samples of the dataset, 2) plotting the multiple intermediate probabilistic estimates against indications of sample size, 3) fitting a function to the plotted data points, and 4) determining an overall distinct value estimate by extrapolating the objective function to an estimated or known total number of values in the dataset.

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San Francisco, CA, United States of America

Mostafa Mokhtar