初步实验使用KV数据库（pebble）存储缓存索引

internal/utils/kvstore/table_field.go

@@ -0,0 +1,41 @@
+// Copyright 2024 GoEdge CDN goedge.cdn@gmail.com. All rights reserved. Official site: https://goedge.cn .
+
+package kvstore
+
+import (
+	"errors"
+)
+
+func (this *Table[T]) AddField(fieldName string) error {
+	if !IsValidName(fieldName) {
+		return errors.New("invalid field name '" + fieldName + "'")
+	}
+
+	// check existence
+	for _, field := range this.fieldNames {
+		if field == fieldName {
+			return nil
+		}
+	}
+
+	this.fieldNames = append(this.fieldNames, fieldName)
+	return nil
+}
+
+func (this *Table[T]) AddFields(fieldName ...string) error {
+	for _, subFieldName := range fieldName {
+		err := this.AddField(subFieldName)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (this *Table[T]) DropField(fieldName string) error {
+	this.mu.Lock()
+	defer this.mu.Unlock()
+
+	var start = this.FieldKey(fieldName + "$")
+	return this.db.store.rawDB.DeleteRange(start, append(start, 0xFF), DefaultWriteOptions)
+}