Time 维度表中满足过滤条件的 time_id 连接键被散列以创建一个位向量，用于过滤以上跳跃式扫描的 Orders 表行。

The time_id join keys that meet the filter requirements on the Time dimension table are hashed to create a bit vector that filters rows of the Orders table from the skip scan above.

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然后针对事实表扫描的每一行，外键也被散列并探测到位向量中，从而判断当前的事实表行是否被过滤掉了。

Then for each row from the fact table scan, the foreign key is also hashed and probed into the bit vector to determine whether the current fact table row is filtered out.

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以扫描向量中的属性频率项作为属性约简搜索的启发信息，提高了属性约简效率。

The item of attribute frequency in the scan vector was taken as heuristic information to improve the efficiency of attributes reduction.

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