Abstract: 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.

Abstract: A scalable job scheduler for a multi-thread, multi-processor system synchronizes and schedules jobs for execution by using lists and jobs counters for the numbers of active jobs. It minimizes synchronization overhead by using atomic operations for incrementing and decrementing the counters. The scheduler assigns jobs for execution, and can awake up an available thread to pick up work. A parent job spawns child jobs and maintains a job counter. Spawned jobs are added to the list for execution and the counter of waiting jobs is incremented. When execution of a job begins, the parent's counter of outstanding child jobs is decremented. A parent job is suspended until its counter of uncompleted spawned child jobs reaches zero. As a job is completed, the scheduler decrements the counter of active jobs, and assigns the next job in the queue to an available thread.

Abstract: Each of a plurality of subtasks is configured to explore and assess alternative solutions for a combinatorial optimization problem by a reentrant finite state machine is represented. Each of a plurality of threads is configured to perform operations comprising a subtask until either completion or a blocked state is reached and, in the event a blocked state is reached, to move on to performing another subtask that is not currently in a blocked state.

Abstract: 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.

Abstract: Server supervisor processes in the segment nodes of a database cluster afford transparent reset mechanisms to a fault tolerant service (FTS). FTS probes only primary segments as to their status unless a primary segment does not respond, in which case FTS will probe the mirror of that primary-mirror pair, and change the state of the mirror to primary if the primary is faulty. Only a primary segment to initiate a reset of its mirror segment and then resets itself. If a mirror segment fails, it shuts down and its corresponding primary segment will report the failure to FTS. Transient communication failures are addressed by retry logic on FTS probing, and not reported to FTS. Reset is not initiated by FTS and preserves the segment state in the absence of errors.

Abstract: 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.

Abstract: Each of a plurality of subtasks is configured to explore and assess alternative solutions for a combinatorial optimization problem by a reentrant finite state machine is represented. Each of a plurality of threads is configured to perform operations comprising a subtask until either completion or a blocked state is reached and, in the event a blocked state is reached, to move on to performing another subtask that is not currently in a blocked state.

Abstract: Each of a plurality of subtasks is configured to explore and assess alternative solutions for a combinatorial optimization problem by a reentrant finite state machine is represented. Each of a plurality of threads is configured to perform operations comprising a subtask until either completion or a blocked state is reached and, in the event a blocked state is reached, to move on to performing another subtask that is not currently in a blocked state.