PaCHash：压缩的哈希表
PaCHash: Packed and Compressed Hash Tables
摘要：
我们引入PaCHash，一个哈希表，它将对象连续存储在一个数组中，即使对象的大小可变，也不需要插入空间。具体地，每个对象可以使用标准压缩技术来压缩。小的搜索数据结构允许在恒定的预期时间内定位对象。PaCHash最自然地被描述为静态外部哈希表，其中它需要每个外部存储器块的内部存储器的恒定位数。在这里，从某种意义上说，PaCHash击败了k-完美散列的空间消耗下限。快速SSD的实现需要每个外部存储器块大约5位的内部存储器，每个搜索操作仅需要一次磁盘访问（可变长度），并且与磁盘访问成本相比具有较小的内部搜索开销。我们的实验表明，即使考虑相同大小的对象，它的空间消耗也比之前所有方法都低。
英文摘要：
We introduce PaCHash, a hash table that stores its objects contiguously in an array without intervening space, even if the objects have variable size. In particular, each object can be compressed using standard compression techniques. A small search data structure allows locating the objects in constant expected time. PaCHash is most naturally described as a static external hash table where it needs a constant number of bits of internal memory per block of external memory. Here, in some sense, PaCHash beats a lower bound on the space consumption of k-perfect hashing. An implementation for fast SSDs needs about 5 bits of internal memory per block of external memory, requires only one disk access (of variable length) per search operation, and has small internal search overhead compared to the disk access cost. Our experiments show that it has lower space consumption than all previous approaches even when considering objects of identical size.
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