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Exection of a physical query plan

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• Ordering of the physical operations
  • Tree shape and data flow:

    The data flows from a child node to a parent node in a physical query plan:

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  • Operator dependency:

    Operations that is a parent/grand-parent/... of some child operand must wait for data from the child: Operations that are siblings (no parent/grand-parent ... child relationship) can proceed simultaneously:

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• Execution of a physical query plan
  • Given: physical query plan

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  • Exection is done as follows:

    Break the query plan tree into sub-tree at each edge that represents materialization: Before After Relationship of the sub-trees is: Execute each sub-tree one-by-one in this order: Bottom-up Left to right (Execute all your children subtree before executing the parent) Each sub-tree (individually) is executed simultaneously using a pipeline: