它也允许我们在部署期间执行广泛的优化，即潜在地扫描字节码和优化代码路径，而不会影响在线系统。

It also allows us to perform extensive optimizations during deployment, potentially scanning byte code and optimizing code paths, without impacting online systems.

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例如，使用不正确的谓词会妨碍优化器使用索引扫描，即使在索引可用的情况下。

For example, improperly coded predicates might prevent the optimizer from using an index scan even when the index is available.

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如果没有创建合适的索引，或者如果索引扫描的成本更高一些，优化器通常就选择表扫描。

The optimizer normally chooses a table scan if no appropriate index has been created or if an index scan would be more costly.

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