https://github.com/bhhbazinga/bplustree
A simple persistent kv store based on B+Tree.
https://github.com/bhhbazinga/bplustree
algorithm bplustree cplusplus kv
Last synced: about 1 month ago
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A simple persistent kv store based on B+Tree.
- Host: GitHub
- URL: https://github.com/bhhbazinga/bplustree
- Owner: bhhbazinga
- Created: 2020-04-02T13:39:47.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2021-03-28T10:31:05.000Z (about 4 years ago)
- Last Synced: 2025-04-23T06:07:15.198Z (about 1 month ago)
- Topics: algorithm, bplustree, cplusplus, kv
- Language: C++
- Homepage:
- Size: 92.8 KB
- Stars: 22
- Watchers: 2
- Forks: 4
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# BPlusTree
A B+ tree is an m-ary tree with a variable but often large number of children per node. A B+ tree consists of a root, internal nodes and leaves. The root may be either a leaf or a node with two or more children.\
The primary value of a B+ tree is in storing data for efficient retrieval in a block-oriented storage context — in particular, filesystems(In my repo, I use mmap.). This is primarily because unlike binary search trees, B+ trees have very high fanout (number of pointers to child nodes in a node, typically on the order of 100 or more), which reduces the number of I/O operations required to find an element in the tree.\
In theory, if the size of the index node in B+ tree is close to the size of the disk block(eg.4k bytes page size in linux), a query operation needs to access the disk logb(N) times.
## Feature
* Use mmap to read and write to disk.
* Use LRU to cache mapped blocks.
## Benchmark
Magnitude | Put | Get | Delete |
:----------- | :-----------| :----------|:-----------|
10K | 72ms | 28ms | 52ms |
100K | 900ms | 507ms | 777ms |
1000K | 10333ms | 4726ms | 8154ms |
The above data was tested on my 2013 macbook-pro with Intel Core i7 4 cores 2.3 GHz.\
Each record has a value length of 100 bytes and I set cache size to 5MB.
See also [test](test.cc).
## Build
```
make && ./test
```
## API
```C++
BPlusTree(const char* path);
void Put(const std::string& key, const std::string& value);
bool Delete(const std::string& key);
bool Get(const std::string& key, std::string& value) const;
std::vector GetRange(const std::string& left, const std::string& right) const;
bool Empty() const;
size_t Size() const;
```
## TODO List
- [ ] Support for variable key-value length.
- [ ] When Dealloc is executed, put block into reuse-pool.
- [ ] Defragment db file.
- [ ] Add WAL(Write Ahead Log).
- [ ] Data compression.
## Reference
[1] https://en.wikipedia.org/wiki/B%2B_tree \
[2] https://www.cnblogs.com/nullzx/p/8729425.html \
[3] http://man7.org/linux/man-pages/man2/mmap.2.html