SQL/MX 3.1 Query Guide (H06.23+, J06.12+)

Compiling and Executing a Query
HP NonStop SQL/MX Release 3.1 Query Guide—663851-001
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How the Executor Processes the Plan
The task model makes it easy to perform all internal operations asynchronously so that
a single server thread can have multiple I/Os outstanding. This model also provides
parallelism for both shared memory and distributed memory architectures. In-memory
queues are used for communication, and exchange operators are used for distributed
memory.
Concurrent or overlapping work can be performed on rows as they flow through the
different stages of the execution plan. For example, while the left child of a nested-loop
join is working on producing more rows or waiting for a reply from a DAM process, the
right child can be working on obtaining matches on the rows already produced by the
left child. For more information about parallelism, see Section 8, Parallelism.
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