在b-树中,您可以将键和数据存储在内部节点和叶节点中,但在b+树中,您必须仅将数据存储在叶节点中。

在b+树中这样做有什么好处吗?

为什么不在所有地方都使用b-树而不是b+树,因为直觉上它们看起来更快?

我的意思是,为什么需要在b+树中复制键(数据)?


当前回答

下图有助于显示B+树和B树之间的区别。

B+树的优点:

Because B+ trees don't have data associated with interior nodes, more keys can fit on a page of memory. Therefore, it will require fewer cache misses in order to access data that is on a leaf node. The leaf nodes of B+ trees are linked, so doing a full scan of all objects in a tree requires just one linear pass through all the leaf nodes. A B tree, on the other hand, would require a traversal of every level in the tree. This full-tree traversal will likely involve more cache misses than the linear traversal of B+ leaves.

B树的优点:

因为B树包含每个键的数据,所以经常访问的节点可以位于更靠近根的位置,因此可以更快地访问。


其他回答

数据库系统概念示例

B+树

相应的b -树

下图有助于显示B+树和B树之间的区别。

B+树的优点:

Because B+ trees don't have data associated with interior nodes, more keys can fit on a page of memory. Therefore, it will require fewer cache misses in order to access data that is on a leaf node. The leaf nodes of B+ trees are linked, so doing a full scan of all objects in a tree requires just one linear pass through all the leaf nodes. A B tree, on the other hand, would require a traversal of every level in the tree. This full-tree traversal will likely involve more cache misses than the linear traversal of B+ leaves.

B树的优点:

因为B树包含每个键的数据,所以经常访问的节点可以位于更靠近根的位置,因此可以更快地访问。


在B+树中,由于只有指针存储在内部节点中,因此它们的大小明显小于B树的内部节点(存储数据+键)。 因此,B+树的索引可以在一次磁盘读取中从外部存储中提取,处理后找到目标的位置。如果它是一个B树,那么每个决策过程都需要读取磁盘。希望我把我的观点讲清楚了!:)

The primary distinction between B-tree and B+tree is that B-tree eliminates the redundant storage of search key values.Since search keys are not repeated in the B-tree,we may not be able to store the index using fewer tree nodes than in corresponding B+tree index.However,since search key that appear in non-leaf nodes appear nowhere else in B-tree,we are forced to include an additional pointer field for each search key in a non-leaf node. Their are space advantages for B-tree, as repetition does not occur and can be used for large indices.

**

B-Tree的主要缺点是遍历键的难度 按顺序。B+树保留了的快速随机访问属性 b -树,同时也允许快速顺序访问

** 参考:Data Structures Using C//作者:Aaro M Tenenbaum

http://books.google.co.in/books?id=X0Cd1Pr2W0gC&pg=PA456&lpg=PA456&dq=drawback+of+B-Tree+is+the+difficulty+of+Traversing+the+keys+sequentially&source=bl&ots=pGcPQSEJMS&sig=F9MY7zEXYAMVKl_Sg4W-0LTRor8&hl=en&sa=X&ei=nD5AUbeeH4zwrQe12oCYAQ&ved=0CDsQ6AEwAg#v=onepage&q=drawback%20of%20B-Tree%20is%20the%20difficulty%20of%20Traversing%20the%20keys%20sequentially&f=false