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Phased ModelIn NebulaStream, we apply a phased optimization and execution model. Common systems like Common database systems use a two-phase approach, i.e., an optimization phase on logical operators and an execution phase on physical operators. In this model, the query is translated in a DAG of logical operators and then into a DAG of physical operators, which are then deployed. In contrast, in NebulaStream we follow the idea of deep optimization, thus our optimization and execution consist of multiple phases. Each phase takes a DAG as an input, applies optimization and conversion on the node, and outputs a valid DAG of operators. However, we employ a rich set of different operators with different granularities and properties, instead of being restricted to logical and physical operators only. After submitting a query via the rest endpoint and the creation of the query plan, the current version of the phase model inside NES contains the following phases (please note that we allow an arbitrary set of phases):
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