这是“外归并排序”能在主存外完成排序的关键步骤 -- 因为“归并算法”(merge algorithm)对每一个大块只是顺序地做一轮访问(进行归并),每个大块不用完全载入主存。
1.3.1. Two-Way External Merge Sort The simplest implementation of external merge sort is the “two-way” external sorting algorithm. We start from a relation R containing a certain amount of records and stored into B pages of a file in secondary storage (and therefore in B blocks of memory...
sorting each chunk, and then merging the sorted chunks together. To illustrate, for sorting 900 megabytes of data with only 100 megabytes of RAM, one can use the external merge sort algorithm as follows: 1. Sort 100 MB of the data by a conventional ...
--设置环境gdb调试setwork_mem=64K;--设置足够小满足外部排序条件createtablea(xint,yint);insertintoaSELECTceil(random()*(10000-1)+1),3fromgenerate_series(1,10000);select*fromaorderbyaasc; 上面的sql执行计划是SortPlan 中挂载SeqScan,SeqScan每扫描一条数据返回SortPLan进行排序处理。我们直接切入函数Exec...
External mergesort, as the classical algorithm of external sorting adopted in many systems and algorithms, has an important impact on the overall performance. Therefore, it is of great significance to optimize and improve the efficiency of external mergesort algorithm. The research work on optimizing...
main memory space-time integral/ C6130 Data handling techniques C4240 Programming and algorithm theory C6120 File organisationThe performance of two basic external sorting algorithms, distributive sorting and mergesort, is compared in an environment where even the main memory usage involves a cost. ...
The name of this algorithm is Natural Two-Way Sort Merge. Obvious lacks of these algorithms are that the first case is not taken into account by the already being order of data, and the second and third does not take into account decreasing OSS. In addition, three buffers are actually ...
Algorithm R已经给出很漂亮的处理。下面是算法demo。 /* Replacement selection */#include<stdio.h>#include<limits.h>#define TOK int/* Type of key; Simplify the key type with integer instead; */#define TRUEMAXKEY INT_MAX/* Larger than any possbile key */#define EOR -1/* End record */#...
Replacement Selection Sort Algorithm —— 置换—选择排序算法 如果要想减小m的值,在外部文件总的记录数n值一定的情况下,只能增加每个归并段中所包含的记录数l 而对于初始归并段的形成,因为所有的内部排序所有的记录都存在于内存中,而内存的可使用的空间有限,如果增加l的值,内存无法存放,可以使用置换—选择排序算法...
External-Memory Sorting in Java: useful to sort very large files using multiple cores and an external-memory algorithm. The versions 0.1 of the library are compatible with Java 6 and above. Versions 0.2 and above require at least Java 8. This code is used in Apache Jackrabbit Oak as well ...