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
107 lines
2.3 KiB
Go
107 lines
2.3 KiB
Go
package btree
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import (
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"sort"
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"github.com/edsrzf/mmap-go"
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)
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// Reader 用于查询 B+Tree (mmap)
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type Reader struct {
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mmap mmap.MMap
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rootOffset int64
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}
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// NewReader 创建查询器
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func NewReader(mmap mmap.MMap, rootOffset int64) *Reader {
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return &Reader{
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mmap: mmap,
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rootOffset: rootOffset,
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}
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}
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// Get 查询 key，返回数据位置
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func (r *Reader) Get(key int64) (dataOffset int64, dataSize int32, found bool) {
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if r.rootOffset == 0 {
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return 0, 0, false
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}
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nodeOffset := r.rootOffset
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for {
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// 读取节点 (零拷贝)
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if nodeOffset+NodeSize > int64(len(r.mmap)) {
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return 0, 0, false
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}
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nodeData := r.mmap[nodeOffset : nodeOffset+NodeSize]
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node := Unmarshal(nodeData)
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if node == nil {
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return 0, 0, false
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}
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// 叶子节点
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if node.NodeType == NodeTypeLeaf {
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// 二分查找
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idx := sort.Search(len(node.Keys), func(i int) bool {
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return node.Keys[i] >= key
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})
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if idx < len(node.Keys) && node.Keys[idx] == key {
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return node.DataOffsets[idx], node.DataSizes[idx], true
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}
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return 0, 0, false
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}
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// 内部节点，继续向下
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// keys[i] 是分隔符，children[i] 包含 < keys[i] 的数据
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// children[i+1] 包含 >= keys[i] 的数据
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idx := sort.Search(len(node.Keys), func(i int) bool {
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return node.Keys[i] > key
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})
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// idx 现在指向第一个 > key 的位置
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// 我们应该走 children[idx]
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if idx >= len(node.Children) {
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idx = len(node.Children) - 1
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}
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nodeOffset = node.Children[idx]
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}
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}
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// GetAllKeys 获取 B+Tree 中所有的 key（按顺序）
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func (r *Reader) GetAllKeys() []int64 {
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if r.rootOffset == 0 {
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return nil
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}
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var keys []int64
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r.traverseLeafNodes(r.rootOffset, func(node *BTreeNode) {
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keys = append(keys, node.Keys...)
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})
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return keys
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}
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// traverseLeafNodes 遍历所有叶子节点
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func (r *Reader) traverseLeafNodes(nodeOffset int64, callback func(*BTreeNode)) {
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if nodeOffset+NodeSize > int64(len(r.mmap)) {
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return
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}
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nodeData := r.mmap[nodeOffset : nodeOffset+NodeSize]
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node := Unmarshal(nodeData)
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if node == nil {
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return
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}
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if node.NodeType == NodeTypeLeaf {
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// 叶子节点，执行回调
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callback(node)
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} else {
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// 内部节点，递归遍历所有子节点
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for _, childOffset := range node.Children {
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r.traverseLeafNodes(childOffset, callback)
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}
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}
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}
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