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@@ -351,6 +351,21 @@ however for some roxie queries (e.g. in a production system) the execution worku
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The following walk-through details the main stages executing a query, and the effect each of the query elements has.
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+Queues
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+======
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+The system uses several inter-process queues to communicate between the different components in the system. These queues
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+are implemented by dali. Components can subscribe to one or more queues, and receive notifications when entries are
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+avaialable.
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+
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+Some example queues are:
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+
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+* <cluster>.eclserver - workunits to be compiled
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+* <cluster>.roxie - workunits to execute on roxie
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+* <cluster>.thor - graphs to execute on thor
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+* <cluster>.eclscheduler - workunits that need to wait for events
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+* <cluster>.agent - workunits to be executed on hthor or thor.
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+* dfuserver_queue - dfu workunits for sprays/file copies etc.
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+
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Workflow
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========
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When a workunit is ready to be run, the workflow controls the flow of execution. The workflow engine
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Richard Chapman