b-tree

I am looking for a lean and well constructed open source implementation of a B-tree library written in C. It needs to be under a non-GPL license so that it can be used in a commercial application. Ideally, this library supports the B-tree index to be stored/manipulated as a disk file so that large trees can be built using a configurable (ie: minimal) RAM footprint. Note: Since there seemed to be some confusion, a Binary Tree and a B-Tree are not the same thing. Paul Check out QDBM: http://fallabs.com/qdbm/ . It's LGPL (can be used in commercial app), implements a disk backed hash and/or B+

I am trying to implement a database index based on the data structure (B link tree) and algorithms suggested by Lehman and Yao in this paper . In page 2, the authors state that: The disk is partitioned in sections of fixed size (physical pages; in this paper, these correspond to the nodes of the tree). These are the only units that can be read or written by a process. [emphasis mine] (...) (...) a process is allowed to lock and unlock a disk page. This lock gives that process exclusive modification rights to that page; also, a process must have a page locked in order to modify that page. (...)

目前大部分数据库系统及文件系统都采用B-Tree或其变种B+Tree作为索引结构，在本文的下一节会结合存储器原理及计算机存取原理讨论为什么B-Tree和B+Tree在被如此广泛用于索引，这一节先单纯从数据结构角度描述它们。 B-Tree 为了描述B-Tree，首先定义一条数据记录为一个二元组[key, data]，key为记录的键值，对于不同数据记录，key是互不相同的；data为数据记录除key外的数据。那么B-Tree是满足下列条件的数据结构： d为大于1的一个正整数，称为B-Tree的度。 h为一个正整数，称为B-Tree的高度。 每个非叶子节点由n-1个key和n个指针组成，其中d<=n<=2d。 每个叶子节点最少包含一个key和两个指针，最多包含2d-1个key和2d个指针，叶节点的指针均为null 。 所有叶节点具有相同的深度，等于树高h。 key和指针互相间隔，节点两端是指针。 一个节点中的key从左到右非递减排列。 所有节点组成树结构。 每个指针要么为null，要么指向另外一个节点。 如果某个指针在节点node最左边且不为null，则其指向节点的所有key小于v(key1)，其中v(key1)为node的第一个key的值。 如果某个指针在节点node最右边且不为null，则其指向节点的所有key大于v(keym)，其中v(keym)为node的最后一个key的值。

I have a large database for solving crossword puzzles, consisting of a word and a description. My application allows searching for words of a specific length and characters on specific positions (this is done the hard way ... go through all words and check each). Plus a search by description (if necessary) For instance find word _ _ A _ _ B (6 letter word, third character A and last B) I would like to index the words in such way that the searching would be really fast. My first idea was to use a balanced tree structure, any other suggestion? Okay, I am going to propose something weird, but

索引的数据结构 索引常用的数据结构为 1.Hash 2.B - tree（B 树） 这两种数据结构是mysql存储索引所采用的数据结构。其中B- tree是mysql比较常用的数据结构 B - tree结构如下： B - tree是由节点和边组成的，且一个节点存储多个关键字，且关键字也会对应记录地址，节点结构如下： 如果查询姓 和名字，则会先查姓，如果这个姓是在子节点中就会进入子节点。因为左原则，查询名字是无法使用索引的，假如名字是“有为”，则可能会出现 康有为 李有为 将有为····等等很多，所以名是无法作为索引的。 来源： https://blog.csdn.net/shanjairui/article/details/100023460

I am looking for a lightweight open source paging B+ tree implementation that uses a disk file for storing the tree. So far I have found only memory-based implementations , or something that has dependency on QT (?!) and does not even compile. Modern C++ is preferred, but C will do too. I prefer to avoid full embeddable DBMS solution, because: 1) for my needs bare bone index that can use the simplest possible disk file organization is enough, no need for concurrency, atomicity and everything else. 2) I am using this to prototype my own index, and most likely will change some of the algorithms

I'm looking for a tool to get a decent estimate of how large a MongoDB index will be based on a few signals like: How many documents in my collection The size of the indexed field(s) The size of the _id I'm using if not ObjectId Geo/Non-geo Has anyone stumbled across something like this? I can imagine it would be extremely useful given Mongo's performance degradation once it hits the memory wall and documents start getting paged out to disk. If I have a functioning database and want to add another index, the only way I'll know if it will be too big is to actually add it. It wouldn't need to be

MySQL支持的索引类型 MySQL支持多种索引类型，每一个存储引擎对其有着不同程度的支持。 MySQL支持以下四种索引，具体支持情况见下表： 索引 MyISAM InnoDB Memory B-Tree 支持 支持 支持 HASH 不支持 不支持 支持 R-Tree 支持 不支持 不支持 Full-Text 支持 不支持 不支持 B-Tree 算是平时用到最多的一种索引类型，大部分引擎都支持。 Hash 目前只有Memory支持，对于等值查询有着较高的效率，不支持范围查询。 R-tree 空间索引，在MyISAM中实现，用于地理位置的查询。 Full-Text 全文索引，紧在MyISAM中支持，MySQL5.6后InnoDB也开始支持。 支持的索引规则 1、最左前缀规则，使用a、b、c联合索引的时候，需要按从左到右的顺序进行SQL的查询，可以包含一部分字段，比如只根据a进行检索也可以使用索引，但是不可以颠倒顺序进行查询。 2、只查询索引中的字段，比如： //简单的登陆SQL，假设username为唯一索引，id为主键 SELECT * FROM user WHERE username = 'fuckphp' AND password = 'fuckphp'; //如上SQL的效率会比下面的效率低 SELECT id FROM user WHERE username =