完成了recover，修复了有关ParseValuede的内存泄漏问题和有关Transput和TransDelete的潜在内存访问异常问题

db/db_impl.cc

@@ -1169,7 +1169,7 @@ Status DBImpl::GetFields(const ReadOptions& options, const Slice& key,
                    FieldArray* fields) {
   std::string value;
   Status s = DBImpl::Get(options, key, &value);
-  *fields = *ParseValue(value);
+  ParseValue(value,fields);
   return s;
 }
 

fielddb/field_db.cpp

@@ -6,10 +6,13 @@
 #include <vector>
 #include "leveldb/db.h"
 #include "leveldb/env.h"
+#include "leveldb/iterator.h"
 #include "leveldb/options.h"
+#include "leveldb/slice.h"
 #include "leveldb/status.h"
 #include "leveldb/write_batch.h"
 #include "db/write_batch_internal.h"
+#include "util/coding.h"
 #include "util/mutexlock.h"
 #include "util/serialize_value.h"
 #include "fielddb/encode_index.h"
@@ -53,7 +56,47 @@ Status FieldDB::OpenFieldDB(const Options& options,
 Status FieldDB::Recover() {
     //TODO:
     //1. 遍历所有Index类型的meta，重建内存中的index_状态表
+    Iterator *Iter = indexDB_->NewIterator(ReadOptions());
+    std::string IndexKey;
+    Iter->SeekToFirst();
+    while(Iter->Valid()) {
+        IndexKey = Iter->value().ToString();
+        ParsedInternalIndexKey ParsedIndex;
+        ParseInternalIndexKey(Slice(IndexKey),&ParsedIndex);
+        index_[ParsedIndex.name_.ToString()] = {Exist,nullptr};
+        std::cout << "Existed Index : " << ParsedIndex.name_.ToString() << std::endl;
+
+        //构建下一个搜索的对象，在原来的fieldname的基础上加一个最大的ascii字符（不可见字符）
+        //TODO：不知道这个做法有没有道理
+        std::string Seek;
+        PutLengthPrefixedSlice(&Seek, ParsedIndex.name_);
+        Seek.push_back(0xff);
+        Iter->Seek(Slice(Seek));
+    }
+    delete Iter;
     //2. 寻找所有KV类型的meta，再次提交一遍请求
+    Iter = metaDB_->NewIterator(ReadOptions());
+    Slice MetaValue;
+    Iter->SeekToFirst();
+    while (Iter->Valid()) {
+        MetaValue = Iter->key();
+        MetaType type = MetaType(DecodeFixed32(MetaValue.data()));
+        MetaValue.remove_prefix(4);//移除头上的metaType的部分
+        if(type == KV_Creating) {
+            FieldArray fields;
+            ParseValue(Iter->value().ToString(), &fields);
+            PutFields(WriteOptions(), MetaValue, fields);
+        } else if(type == KV_Deleting) {
+            Delete(WriteOptions(), MetaValue);
+        } else {
+            assert(0 && "Invalid MetaType");
+        }
+    }
+    delete Iter;
+    //在所有的请求完成后，会自动把metaDB的内容清空。
+    Iter = metaDB_->NewIterator(ReadOptions());
+    Iter->SeekToFirst();
+    std::cout << "Iter Valid : " << Iter->Valid() << std::endl; 
     //3. 等待所有请求完成
     return Status::OK();
 }

fielddb/meta.cpp

@@ -22,22 +22,24 @@ using namespace leveldb;
 
 
 //对于含有index field的put/delete的meta编码为 (KV|Key,Value)
-void MetaKV::TransPut(Slice &MetaKey,Slice &MetaValue) {
+void MetaKV::TransPut(std::string &MetaKey,std::string &MetaValue) {
     MetaKey.clear();
     MetaValue.clear();
-    std::string buf;
+    //这里的改动是为了防止潜在的段错误。原来的写法中，slice(buf)对应的buf是局部的，在函数返回后，buf被销毁
+    //但是slice中的指针指向的是析构的string对象的部分内存
+    std::string &buf = MetaKey; 
     PutFixed32(&buf, KV_Creating);
     PutLengthPrefixedSlice(&buf, Slice(*name));
-    MetaKey = Slice(buf);
-    MetaValue = Slice(*value);
+    // MetaKey = Slice(buf);
+    // MetaValue = Slice(*value);
 }
 
-void MetaKV::TransDelete(Slice &MetaKey) {
+void MetaKV::TransDelete(std::string &MetaKey) {
     MetaKey.clear();
-    std::string buf;
+    std::string &buf = MetaKey;
     PutFixed32(&buf, KV_Deleting);
     PutLengthPrefixedSlice(&buf, Slice(*name));
-    MetaKey = Slice(buf);
+    // MetaKey = Slice(buf);
 }
 
 class CleanerHandler : public WriteBatch::Handler {

fielddb/meta.h

@@ -37,8 +37,8 @@ class MetaKV {
 public:
     MetaKV(std::string *field_name,std::string *field_value = nullptr):
         name(field_name),value(field_value) { }
-    void TransPut(Slice &MetaKey,Slice &MetaValue);
-    void TransDelete(Slice &MetaKey);
+    void TransPut(std::string &MetaKey,std::string &MetaValue);
+    void TransDelete(std::string &MetaKey);
 private:
     std::string *name;
     std::string *value;

fielddb/request.cpp

@@ -1,5 +1,6 @@
 #include "fielddb/request.h"
 #include <cassert>
+#include <string>
 #include "leveldb/slice.h"
 #include "leveldb/status.h"
 #include "leveldb/write_batch.h"
@@ -54,7 +55,8 @@ void FieldsReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
     if (s.IsNotFound()){
         oldFields = nullptr;
     } else if (s.ok()) { //得到数据库之前key的fields, 判断需不需要删除其中潜在的索引
-        oldFields = ParseValue(val_str);        
+        oldFields = new FieldArray;
+        oldFields = ParseValue(val_str,oldFields);        
     } else {
         assert(0);
     }
@@ -99,11 +101,11 @@ void FieldsReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
 
         //2.对于没有冲突但含有索引操作的put，构建metaKV，这里直接将KV对简单编码后写入metaDB
         if(HasIndex || HasOldIndex) {
-            Slice MetaKey,MetaValue;
+            std::string MetaKey,MetaValue;
             std::string serialized = SerializeValue(*Fields);
             MetaKV MKV = MetaKV(Key,&serialized);
             MKV.TransPut(MetaKey, MetaValue);
-            MetaBatch.Put(MetaKey, MetaValue);
+            MetaBatch.Put(MetaKey, serialized);
             
         
         //3.1对于含有索引的oldfield删除索引
@@ -135,6 +137,8 @@ void FieldsReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
         }
         //优化：对于3.1，3.2中都有的索引只写一次
     }
+
+    if(oldFields) delete oldFields;
 }
 
 
@@ -154,7 +158,9 @@ void DeleteReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
     //2.3 如果存在field的索引状态是Creating或者Deleting，那么在那个队列上面进行等待
     std::string val_str;
     DB->kvDB_->Get(ReadOptions(), *Key, &val_str);
-    FieldArray *Fields = ParseValue(val_str);
+    FieldArray *Fields = new FieldArray;
+    ParseValue(val_str,Fields); 
+
     KVBatch.Delete(Slice(*Key));
     bool HasIndex = false;
     {
@@ -176,7 +182,7 @@ void DeleteReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
         }
         //2.对于没有冲突但含有索引操作的delete，构建metaKV，这里直接将KV对简单编码后写入metaDB
         if(HasIndex) {
-            Slice MetaKey;
+            std::string MetaKey;
             MetaKV MKV = MetaKV(Key);
             MKV.TransDelete(MetaKey); //meta中写入一个delete不需要value
             MetaBatch.Put(MetaKey, Slice());
@@ -192,6 +198,7 @@ void DeleteReq::ConstructBatch(WriteBatch &KVBatch,WriteBatch &IndexBatch,
             }
         }
     }
+    delete Fields;
 }
 
 /*******iCreateReq*******/

util/serialize_value.cc

@@ -20,9 +20,10 @@ std::string SerializeValue(const FieldArray& fields){
     return result;
 }
 
-FieldArray *ParseValue(const std::string& value_str){
+FieldArray *ParseValue(const std::string& value_str,FieldArray *fields){
     Slice valueSlice(value_str);
-    FieldArray *res = new FieldArray;
+    // FieldArray *res = new FieldArray;
+    FieldArray *res = fields;
     Slice nameSlice = Slice();
     Slice valSlice = Slice();
     std::string nameStr;

util/serialize_value.h

@@ -12,7 +12,7 @@ using Field = std::pair;	  // field_name:field_value
 using FieldArray = std::vector<std::pair<std::string, std::string>>;
 
 std::string SerializeValue(const FieldArray& fields);
-FieldArray *ParseValue(const std::string& value_str);
+FieldArray *ParseValue(const std::string& value_str, FieldArray *fields);
 
 class InternalFieldArray {
 public: