The optimizer considers star join optimization when appropriate and decides on star join plan based on cost considerations in order to come up with best execution plan for a star join query.
为了实现星型连接查询的最佳执行计划，优化器在适当的时候会考虑星型连接优化，并根据成本因素来决定星型连接计划。
Query optimization is the main problem of query processing research, thus in particular discusses cost estimated, query plan, search Spaces and so on related problems.
查询优化是查询处理研究的一个主要问题，为此着重分析研究了查询优化所涉及的代价估计、查询规划和搜索空间等相关问题。
In plan optimization module, the access path selection and the account method of cost evaluation are discussed in detail.
在计划优化模块中，详细讨论了存取路径的选择和代价评估的计算方法。
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