891.txt

This complete matlab for neural network

发信人: fervvac (高远), 信区: DataMining
标  题: Re: 数据仓库里的实体化视图怎么实现？
发信站: 南京大学小百合站 (Thu Sep 12 11:52:42 2002), 站内信件

1. MV/cube is usually much larger than available memory, thus you cannot 
   put it entirely in the memory.

   To quickly return a precomputed result from the MV/cube, you need to index
   it. Either the traditional index or some new ones can be used. Related 
   techniques includeub-tree, cubetree, etc.
   Ross has an interesting paper in ssdbm (2000?) about actively caching 
   part of the cube in memory.

2. Not sure why you think it is difficult to store your result in a file. This
   method, although slower, only requires basic knowledge of C/C++. Find any
   c/c++ book and read the i/o part. btw, you need to map dimension values to
   integer first.

【 在 netsaint (大圣) 的大作中提到: 】
: 一般的ROLAP确实把这种数据存放在关系表里
: 我把这些数据存放在临时文件里是出于这样的目的：
: 把这些文件常驻内存，这样，对每个请求，首先去查询内存中的文件
: 如果找不到结果，再去数据库检索关系表
: 是否可行？
: 对于这个临时文件怎么去统一它的格式，还有怎样去读取里面的数据（好像要对字符串读
: 取和处理的）？
: 头都大了
: 
: 【 在 fervvac 的大作中提到: 】
: : For any serious implementation, it is a bad idea to store data in text 
: : format. 
: : First of all, you need to know which type of system you have, ROLAP or MOL..
: : Chunk is only used in MOLAP, and relations are only used in ROLAP.
: : The basic method to store data in ROLAP is to store in relational table(s).
: : You can either create a table with all dimension attributes  pulus the mea..
: : attribture, or use multiple tables, each for a cuboid. So there is no 
: : fundamental difficulty  there.
: : For chunks, I am not sure of the real implementation of commercial systems.
: : For most prototype systems, the problem is that "extra-long" integer type 
: (以下引言省略 ... ...)

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