英语翻译Note that despite RLE and bit-vector encoding being verydifferent compression techniques,the pseudocode in Figure 2need not distinguish between them,pushing the complexityof calculating the block size into the compressed block code.In bot
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英语翻译Note that despite RLE and bit-vector encoding being verydifferent compression techniques,the pseudocode in Figure 2need not distinguish between them,pushing the complexityof calculating the block size into the compressed block code.In bot
英语翻译
Note that despite RLE and bit-vector encoding being very
different compression techniques,the pseudocode in Figure 2
need not distinguish between them,pushing the complexity
of calculating the block size into the compressed block code.
In both cases,the size of the block can be calculated without
block decompression.
Figure 3 gives some more examples of how join and gener-
alized aggregation operators can take advantage of operating
on compressed data given block properties.
In summary,by using compressed blocks as an intermedi-
ate representation of data,operators can operate directly
on compressed data whenever possible,and can degener-
ate to a lazy decompression scheme when this is impossible
(by iterating through block values).Further,by abstracting
general properties about compression techniques and hav-
ing operators check these properties rather than hardcoding
knowledge of a specific compression algorithm,operators are
shielded from needing knowledge about the way data is en-
coded.They simply have to condition for these basic prop-
erties of the blocks of data they receive as input.We have
found that this architecture significantly reduces the query
executor complexity while still allowing direct operation on
compressed data whenever possible.
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英语翻译Note that despite RLE and bit-vector encoding being verydifferent compression techniques,the pseudocode in Figure 2need not distinguish between them,pushing the complexityof calculating the block size into the compressed block code.In bot
注意,尽管RLE和位向量编码有相当大的区别,但在Figure 2的伪代码中并不需要对它们进行区分,把块大小计算的复杂程度交给压缩块代码.在这两种情况中,块的大小不用解压缩就可以计算出来.
Figure 3 提供了多一些 连接和广义的聚合操作符 如何 利用 压缩带有块性质的数据的操作 的样例
总结,通用使用压缩块作为数据的中间表示,在可能的时候,操作符可以直接地操作压缩数据,反之,操作符会退化成惰性解压方案(通过遍历块值).进一步,通过抽象关于压缩技术的普遍性质 和 使用操作符检查这些性质而不是一个特定压缩算法的硬编码,操作符避免了数据解码的必要知识.他们只需要对这些他们作为输入接收的块数据基本性质有所准备
我们发现在仍然允许对压缩数据直接操作时,可能的话,这种结构大大地减少了查询执行的复杂度.