Micro Focus Lcc

Thao Nguyen Pham

Yuanzhe Bei

Hoa Binh Nga Tran

Alexander Kalinin

Michael Leuchtenburg

In multi-threaded or multi-processor computing systems, a deadlock may occur when two or more processes or threads are unable to proceed because they are each waiting for a resource that the other holds. As a result, progress is halted because conflicting entities are stuck in a circular dependency, and none can release the resources they hold to let the others continue. Systems and methods are provided wherein a resource reservation is carried out in two steps. The first step causes query nodes to add an identifier to a queue and, upon a request and the identifier being in a first position, a non-sharable resource is reserved. As a result, non-sharable resources are reserved in order and when needed, thereby preventing deadlocks.

Deadlock prevention utilizing distributed resource reservations

A flattened table (FT) of a database of a database management system (DBMS) is defined. The FT logically materializes a number of columns over a number of partitions. The columns include normalized columns, denormalized columns from a plurality of source tables of the database, as well as an aggregate column defining an aggregation of a selected normalized column over a selected denormalized column. A live-aggregate projection (LAP) is defined on the FT of the database. The LAP corresponds to the aggregate column and physically materializes the aggregation of the selected denormalized column over the selected denormalized column, as defined by the aggregate column. The FT is refreshed on-demand, on a per-column, per-partition basis. Responsive to the FT being refreshed on-demand, the LAP is automatically refreshed.

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Cambridge, MA, United States of America

Thao Nguyen Pham