Optimizer architecture

The Query Optimizer contains many optimization phases that each perform different functions. The different phases help the Query Optimizer perform the highest-value operations earliest in the optimization process.

The major phases in the optimization of a query, as shown in Figure 11-14, are as follows:

  • Simplification

  • Trivial plan

  • Auto-stats create/update

  • Exploration/implementation (phases)

  • Convert to executable plan

A Query Optimizer pipeline.

Figure 11-14. Query Optimizer pipeline.

Before optimization

The SQL Server query processor performs several steps before the actual optimization process begins. These transformations help shape the tree into a form that’s ...

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