Pivotal Software, Inc.

Emc Corporation

Venkatesh Raghavan

Florian Michael Waas

Sivaramakrishnan Narayanan

Mohamed A Soliman

Lyublena Rosenova Antova

Michail Petropoulos

George Constantin Caragea

Konstantinos Krikellas

Amr El-Helw

Mohamed F Soliman

Carlos Garcia-Alvarado

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for generating query plans for queries that include common table expressions. One of the methods includes receiving a query that includes a common table expression (CTE), wherein the CTE signifies that a system can compute a result for the query using a query plan that includes a CTE producer operator and a corresponding CTE consumer operator. A first query plan that includes a CTE producer operator and a corresponding CTE consumer operator and a second query plan that inlines an instance of the CTE consumer operator are generated. Respective costs are computed for the first query plan and the second query plan, and a result for the query is computed using the second query plan if the second query plan has a lower cost.

Query plan generation for common table expressions

Methods, systems, and apparatus, including computer programs encoded on computer storage media, for generating query plans for queries that include common expressions. One of the methods includes receiving an initial query plan generated for a query that includes multiple common expressions; identifying two or more matching subtrees of the initial query plan; generating an alternative query plan that includes a CTE producer operator and having an instance of one of the matching subtrees as one or more descendant operators of the CTE producer operator, including replacing at least one instance of a matching subtree in the initial query plan with a CTE consumer operator corresponding to the CTE producer operator; computing respective costs for the initial query plan and the alternative query plan; selecting the alternative query plan based on the cost for the alternative query plan; and computing a result for the query using the alternative query plan instead of the initial query plan.

Query plan generation for queries having common expressions

A request for a metadata object is received where the request includes an identifier. It is determined whether the metadata object is stored in a metadata cache, including by: selecting a sub-cache in the metadata cache based at least in part on the identifier and determining whether the metadata object is stored in that sub-cache. If it is determined the metadata object is not in the metadata cache, a request (in a format associated with the source) to obtain the metadata object is sent to a source with which the metadata object is associated. If the metadata object provided by the source is in a native format which is not the same as the common format, the metadata object is transformed from the native format into the common format. Access to the metadata object in the common format is provided.

Metadata cache supporting multiple heterogeneous systems

Data movement driven placement of data in a distributed database is disclosed. A set of one or more queries anticipated to be performed with respect to a data set is received. A set of statistics associated with the data set is received. The set of queries and the statistics are used to explore algorithmically a search space of distribution policy alternatives, to determine an optimal distribution policy to distribute data comprising the data set across a plurality of database servers.

Data movement driven automatic data placement

A request for a metadata object is received. It is determined whether the metadata object is stored in a metadata cache. In the event the metadata object is not stored in the metadata cache, a request to obtain the metadata object is sent to a source with which the metadata object is associated in a format associated with the source. The metadata object is transformed from a native format of the source into a common format if the metadata object as provided by the source is in a native format that is not the same as the common format. Access to the metadata object in the common format is provided.

Growing community of inventors

Sunnyvale, CA, United States of America

Venkatesh Raghavan