A storage scheme for multidimensional data alleviating dimension dependency
A storage scheme for multidimensional data alleviating dimension dependency
复制标题
一种缓解维度依赖性的多维数据存储方案
DOI：
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复制
发表时间：
2008
期刊：
影响因子：
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通讯作者：
K. Higuchi
中科院分区：
文献类型：
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作者：
Teppei Shimada;T. Tsuji;K. Higuchi
在MOLAP中存储多维数据的多维数组通常非常稀疏。它们还存在这样一个问题，即顺序访问数组元素所花费的时间在很大程度上取决于访问这些元素的维度。通过将整个阵列分成一组更小的超立方体形子阵列(称为IdquochunkRdQuo)，将缓解Idquue维度依赖RdQuo的问题。但是块也是稀疏的，应该被压缩。然而，除非在页面缓冲区中明智地排列这些压缩块，否则在访问数组元素时会导致进一步的维度依赖。维度基数之间的差异也可能导致维度依赖；沿基数较大的维度进行切片操作往往会耗费大量时间。我们将通过引入扩展块的概念来缓解这两种维度依赖。扩展块可以灵活地适应块中数据密度低且分布不均匀的一般情况。利用扩展块，我们将提出一些使用空间填充曲线的多维阵列的二次存储方案，例如Z-CURE。评估结果表明，所提出的存储方案具有良好的性能，同时降低了对维度的依赖。
Multidimensional arrays storing multidimensional data in MOLAP are usually very sparse. They also suffer from the problem that the time consumed in sequential access to array elements heavily depends on the dimension along which the elements are accessed. This problem of ldquodimension dependencyrdquo would be alleviated by dividing the whole array into the set of smaller hypercube shaped subarrays called ldquochunksrdquo. But the chunks are also sparse and should be compressed. However, further dimension dependency in accessing array elements would be caused, unless these compressed chunks are arranged judiciously in the page buffer. The difference among the dimension cardinalities could also cause dimension dependency; slice operation along a dimension of large cardinality tends to consume much time. We will alleviate these two kinds of dimension dependency by introducing the notion of an ldquoextended chunkrdquo. Extended chunks can adapt flexibly to the general situation where data densities in chunks are low and are not uniformly distributed. Employing extended chunks, we will propose some secondary storage schemes for a multidimensional array using a space-filling curve such as Z-curve. The evaluation result shows that the proposed storage schemes exhibit good performance while alleviating the dimension dependency.