TsDB2/DB/index/str_handler.go

package index

import (
	"TsDB2/DB/index/btree"
	"TsDB2/DB/page"
	"encoding/binary"
)

func init() {
	Compose.RegisterHandler(page.IndexTypeStr, &StrBTreeHandler{})
}

// StrBTreeHandler — 字符串二级索引 (IndexTypeStr)
// 叶子条目: [key(keyLen) + PKID(8B BE)]
// 使用 B+ 树结构替代扁平链表，支持 O(log n) 插入/查询
type StrBTreeHandler struct{}

func (h *StrBTreeHandler) Insert(handle page.HandleDb, entryPage *uint32, indexKey []byte, pkID uint64, rowData []byte, keyLen int) (uint32, error) {
	// 保护：截断 indexKey 防止越界
	if len(indexKey) > keyLen {
		indexKey = indexKey[:keyLen]
	}
	entry := make([]byte, keyLen+8)
	copy(entry[:keyLen], indexKey)
	binary.BigEndian.PutUint64(entry[keyLen:], pkID)
	rootPID := *entryPage
	newRoot, err := btree.StrBTInsert(rootPID, entry, handle)
	if err != nil {
		return 0, err
	}
	*entryPage = newRoot
	return newRoot, nil
}

func (h *StrBTreeHandler) Search(handle page.HandleDb, entryPage uint32, indexKey []byte, keyLen int) ([]byte, bool) {
	rootPID := entryPage
	if rootPID == 0 {
		return nil, false
	}
	pkID, found := btree.StrBTSearch(rootPID, indexKey[:keyLen], handle)
	if !found {
		return nil, false
	}
	pkBuf := make([]byte, 8)
	binary.BigEndian.PutUint64(pkBuf, pkID)
	return pkBuf, true
}

func (h *StrBTreeHandler) Delete(handle page.HandleDb, entryPage *uint32, indexKey []byte, keyLen int) error {
	// 二级索引删除：需要同时匹配 key + pkID
	rootPID := *entryPage
	if rootPID == 0 {
		return page.ErrNotFound
	}
	// 先搜索获取 pkID（假设是精确匹配场景）
	pkIDBuf, found := h.Search(handle, rootPID, indexKey, keyLen)
	if !found {
		return page.ErrNotFound
	}
	pkID := binary.BigEndian.Uint64(pkIDBuf)
	// 调用底层删除（同时匹配 key + pkID），使用正确的 keyLen
	actualKeyLen := len(indexKey)
	if actualKeyLen > keyLen {
		actualKeyLen = keyLen
	}
	newRoot, err := btree.StrBTDeleteWithPKID(rootPID, indexKey[:actualKeyLen], pkID, handle)
	if err != nil {
		return err
	}
	*entryPage = newRoot
	return nil
}

func (h *StrBTreeHandler) Update(handle page.HandleDb, entryPage *uint32, oldKey []byte, rowData []byte, pkID uint64, keyLen int) error {
	// 二级索引 Update: 先删旧条目, 再插新条目
	// 注意：这里 oldKey 是旧索引键，但接口限制无法传入 newKey
	// IndexMetaPage.UpdateByKey 应该传入正确的 newKey 作为 oldKey 参数
	if err := h.Delete(handle, entryPage, oldKey, keyLen); err != nil {
		return err
	}
	// 保护：截断防止越界
	actualKeyLen := len(oldKey)
	if actualKeyLen > keyLen {
		actualKeyLen = keyLen
	}
	_, err := h.Insert(handle, entryPage, oldKey[:actualKeyLen], pkID, rowData, keyLen)
	return err
}

// SearchAll 查找相同 key 下的所有 pkID
func (h *StrBTreeHandler) SearchAll(handle page.HandleDb, entryPage uint32, indexKey []byte, keyLen int) ([]uint64, bool) {
	rootPID := entryPage
	if rootPID == 0 {
		return nil, false
	}
	return btree.StrBTSearchAll(rootPID, indexKey[:keyLen], handle)
}

func (h *StrBTreeHandler) GetDataPageIDs(handle page.HandleDb, entryPage uint32) []uint32 {
	// 二级索引没有 DataPage, 返回空
	return nil
}

func (h *StrBTreeHandler) ReadDataPageRows(handle page.HandleDb, dpID uint32) [][]byte {
	// 二级索引没有 DataPage
	return nil
}

func (h *StrBTreeHandler) RangeScan(handle page.HandleDb, entryPage uint32,
	startKey, endKey []byte, startInclusive, endInclusive bool, reverse bool,
	callback func(row []byte) bool) error {
	return btree.StrBTRangeScan(entryPage, handle, startKey, endKey, startInclusive, endInclusive, reverse, callback)
}