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Cost-Based Optimization of Integration Flows - Datenbanken ...

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6 On-Demand Re-<strong>Optimization</strong><br />

(a) Selectivity Variations<br />

(b) Input Data Size Variations<br />

(c) <strong>Optimization</strong> Time<br />

(d) Execution Time<br />

(e) Cumulative <strong>Optimization</strong> Time<br />

(f) Cumulative Execution Time<br />

Figure 6.14: Simple-Flow Comparison Scenario<br />

cardinalities and operator selectivities. When using periodical re-optimization, the <strong>of</strong>ten<br />

re-occurring small peaks are caused by the numerous asynchronous re-optimization steps.<br />

A major characteristic <strong>of</strong> periodical re-optimization is that after a certain workload shift,<br />

it takes a while until periodical re-optimization is triggered. During this time, the plan<br />

execution time is much longer than the execution time <strong>of</strong> the optimal plan. In contrast, on-<br />

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