The bit vector occupies ( n_nullable + 7 ) / 8 bytes. 位向量(BV)占用了(可空的列数+7)/8字节。
The record header contains a bit vector for indicating NULL columns. 记录头包含一个位向量(BV),用来指明空列。
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. 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(BV)中,从而判断当前的事实表行是否被过滤掉了。
In a bit-vector pushdown, for each push-down, the database server hashes the keys from the dimension table to create a bit vector, which is shipped to the fact table. 在位向量(BV)下推中,对于每次下推,数据库服务器通过散列维度表中的键来创建发送至事实表的位向量(BV)。
Based on intensive study of bitmap compressions, we proposed a rich-extend partition bitmap index approach and a self-adaptive partition word-aligned bit vector compression approach ( APWAH ). 特别对位图压缩技术进行了深入的研究,提出了一种富扩展划分位图索引和一种自适应的划分字对齐压缩方法(APWAH)。