bourdon
ae87c38776
- Core engine with MemTable, SST, WAL - B+Tree indexing for SST files - Leveled compaction strategy - Multi-table database management - Schema validation and secondary indexes - Query builder with complex conditions - Web UI with HTMX for data visualization - Command-line tools for diagnostics
153 lines
2.9 KiB
Go
153 lines
2.9 KiB
Go
package sst
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import (
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"encoding/json"
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"fmt"
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"os"
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"code.tczkiot.com/srdb/btree"
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"github.com/edsrzf/mmap-go"
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"github.com/golang/snappy"
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)
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// Reader SST 文件读取器
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type Reader struct {
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path string
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file *os.File
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mmap mmap.MMap
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header *Header
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btReader *btree.Reader
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}
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// NewReader 创建 SST 读取器
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func NewReader(path string) (*Reader, error) {
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// 1. 打开文件
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file, err := os.Open(path)
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if err != nil {
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return nil, err
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}
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// 2. mmap 映射
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mmapData, err := mmap.Map(file, mmap.RDONLY, 0)
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if err != nil {
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file.Close()
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return nil, err
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}
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// 3. 读取 Header
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if len(mmapData) < HeaderSize {
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mmapData.Unmap()
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file.Close()
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return nil, fmt.Errorf("file too small")
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}
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header := UnmarshalHeader(mmapData[:HeaderSize])
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if header == nil || !header.Validate() {
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mmapData.Unmap()
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file.Close()
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return nil, fmt.Errorf("invalid header")
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}
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// 4. 创建 B+Tree Reader
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btReader := btree.NewReader(mmapData, header.RootOffset)
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return &Reader{
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path: path,
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file: file,
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mmap: mmapData,
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header: header,
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btReader: btReader,
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}, nil
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}
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// Get 查询一行数据
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func (r *Reader) Get(key int64) (*Row, error) {
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// 1. 检查范围
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if key < r.header.MinKey || key > r.header.MaxKey {
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return nil, fmt.Errorf("key out of range")
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}
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// 2. 在 B+Tree 中查找
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dataOffset, dataSize, found := r.btReader.Get(key)
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if !found {
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return nil, fmt.Errorf("key not found")
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}
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// 3. 读取数据
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if dataOffset+int64(dataSize) > int64(len(r.mmap)) {
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return nil, fmt.Errorf("invalid data offset")
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}
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compressed := r.mmap[dataOffset : dataOffset+int64(dataSize)]
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// 4. 解压缩
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var data []byte
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var err error
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if r.header.Compression == CompressionSnappy {
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data, err = snappy.Decode(nil, compressed)
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if err != nil {
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return nil, err
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}
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} else {
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data = compressed
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}
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// 5. 反序列化
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row, err := decodeRow(data)
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if err != nil {
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return nil, err
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}
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return row, nil
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}
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// GetHeader 获取文件头信息
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func (r *Reader) GetHeader() *Header {
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return r.header
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}
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// GetPath 获取文件路径
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func (r *Reader) GetPath() string {
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return r.path
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}
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// GetAllKeys 获取文件中所有的 key（按顺序）
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func (r *Reader) GetAllKeys() []int64 {
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return r.btReader.GetAllKeys()
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}
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// Close 关闭读取器
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func (r *Reader) Close() error {
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if r.mmap != nil {
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r.mmap.Unmap()
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}
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if r.file != nil {
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return r.file.Close()
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}
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return nil
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}
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// decodeRow 解码行数据
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func decodeRow(data []byte) (*Row, error) {
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// 尝试使用二进制格式解码
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row, err := decodeRowBinary(data)
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if err == nil {
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return row, nil
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}
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// 降级到 JSON (兼容旧数据)
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var decoded map[string]interface{}
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err = json.Unmarshal(data, &decoded)
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if err != nil {
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return nil, err
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}
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row = &Row{
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Seq: int64(decoded["_seq"].(float64)),
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Time: int64(decoded["_time"].(float64)),
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Data: decoded["data"].(map[string]interface{}),
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}
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return row, nil
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}
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