对象代理数据库的双向指针存储优化方法
发布时间：2019-05-13 18:01
【摘要】：在对象代理数据库中,提出了两个新的概念:代理对象和代理类.一个对象可以有一个或多个代理对象,该对象也被称为代理对象的源对象.代理对象可以从其源对象中选择性继承属性和方法,也可以扩展定义代理类自己的属性和方法.代理对象继承自源对象的属性称为虚属性,虚属性不实际存储其值,而是在查询时根据源对象的实属性值计算得到.对象代理数据库利用双向指针表来实现源对象和代理对象之间的这种关联,双向指针表中每一条记录包含两个字段,分别对应于源对象ID和代理对象ID.当存在多层代理关系时,查询代理对象需要对双向指针表执行多次查询操作,因而查询效率往往不是很好.文中针对代理对象查询效率低的问题进行了深入研究,发现其主要原因是双向指针表中具有相同代理类和源类的数据分布在不同的磁盘块中,查询双向指针表时需要多次I/O操作.基于此,文中首先设计新的对象代理数据库中空闲空间分配策略,在原有的空闲空间管理策略中加入新的索引信息,使得当需要添加记录时不仅使用空闲空间管理模块FSM查找空闲空间大小一个条件,而且结合使用索引中指定的聚簇信息寻找具有合适空闲空间的磁盘块,然后读取目标磁盘块到内存中,并将双向指针表中的元组以源类和代理类为单位进行分类写入磁盘块,从而实现基于代理关系的双向指针表的聚簇存储.同时针对具体的应用场景,文中根据数据库模式中代理层次信息、用户查询频率等因素设计一个I/O查询代价模型,利用该模型计算各级代理类与源类聚簇之后的查询代价,从而选择出一种查询代价最小,性能最优的聚簇策略,使得能够最大限度的减少I/O次数,提高代理对象的查询效率.实验结果表明,该聚簇方法在真实数据集上的优化效果比未优化平均提高15%以上,比已有的双向指针表的优化方法平均提高9%以上.
[Abstract]:In the object proxy database, two new concepts are proposed: proxy object and proxy class. An object can have one or more proxy objects, also known as the source object of the proxy object. A proxy object can selectively inherit properties and methods from its source object, or it can extend the properties and methods that define the proxy class itself. The proxy object inherits the property from the source object called virtual attribute, which does not actually store its value, but is calculated according to the real property value of the source object when querying. The object proxy database uses a bidirectional pointer table to achieve this association between the source object and the proxy object. Each record in the bidirectional pointer table contains two fields, corresponding to the source object ID and the proxy object ID., respectively. When there is a multi-layer proxy relationship, the query agent object needs to perform multiple query operations on the bidirectional pointer table, so the query efficiency is often not very good. In this paper, the problem of low query efficiency of proxy object is deeply studied, and it is found that the main reason is that the data with the same proxy class and source class in the bidirectional pointer table are distributed in different disk blocks. Multiple I / O operations are required to query the bidirectional pointer table. Based on this, this paper first designs a new free space allocation strategy in the object agent database, and adds new index information to the original free space management strategy. So that when a record needs to be added, not only the free space management module FSM is used to find a condition for the free space size, but also the clustering information specified in the index is used to find the disk block with the appropriate free space, Then the target disk block is read into memory, and the tuples in the bidirectional pointer table are classified and written to the disk block in the units of the source class and the proxy class, so as to realize the clustering storage of the bidirectional pointer table based on the proxy relationship. At the same time, according to the information of agent level in database schema and the frequency of user query, an I 鈮，
本文编号：2476078
[Abstract]:In the object proxy database, two new concepts are proposed: proxy object and proxy class. An object can have one or more proxy objects, also known as the source object of the proxy object. A proxy object can selectively inherit properties and methods from its source object, or it can extend the properties and methods that define the proxy class itself. The proxy object inherits the property from the source object called virtual attribute, which does not actually store its value, but is calculated according to the real property value of the source object when querying. The object proxy database uses a bidirectional pointer table to achieve this association between the source object and the proxy object. Each record in the bidirectional pointer table contains two fields, corresponding to the source object ID and the proxy object ID., respectively. When there is a multi-layer proxy relationship, the query agent object needs to perform multiple query operations on the bidirectional pointer table, so the query efficiency is often not very good. In this paper, the problem of low query efficiency of proxy object is deeply studied, and it is found that the main reason is that the data with the same proxy class and source class in the bidirectional pointer table are distributed in different disk blocks. Multiple I / O operations are required to query the bidirectional pointer table. Based on this, this paper first designs a new free space allocation strategy in the object agent database, and adds new index information to the original free space management strategy. So that when a record needs to be added, not only the free space management module FSM is used to find a condition for the free space size, but also the clustering information specified in the index is used to find the disk block with the appropriate free space, Then the target disk block is read into memory, and the tuples in the bidirectional pointer table are classified and written to the disk block in the units of the source class and the proxy class, so as to realize the clustering storage of the bidirectional pointer table based on the proxy relationship. At the same time, according to the information of agent level in database schema and the frequency of user query, an I 鈮，
本文编号：2476078
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