更新 'leveldb_base/db/memtable.cc'

leveldb_base/db/memtable.cc

@@ -106,6 +106,7 @@ void MemTable::Add(SequenceNumber s, ValueType type, const Slice& key,
   table_.Insert(buf);
 }
 
+//修改memtable读取逻辑-陈予曈
 bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
   Slice memkey = key.memtable_key();
   Table::Iterator iter(&table_);
@@ -130,30 +131,30 @@ bool MemTable::Get(const LookupKey& key, std::string* value, Status* s) {
       switch (static_cast<ValueType>(tag & 0xff)) {
         case kTypeValue: {
           Slice v = GetLengthPrefixedSlice(key_ptr + key_length);
-          // 过期则读取不到-柠
+          // 数据过期则读取不到-陈予曈
           std::string value_with_ttl(v.data(), v.size());
           if (value_with_ttl.size() >= 19) {
             std::string expiration_time_str = value_with_ttl.substr(value_with_ttl.size() - 19); // 提取过期时间戳
             std::tm tm = {};
             char* res = strptime(expiration_time_str.c_str(), "%Y-%m-%d %H:%M:%S", &tm);
-            if (res == nullptr) {
+            if (res == nullptr) {  //解析时间戳失败
               value->assign(v.data(), v.size()-19);
               return true;
             } else {
               std::time_t expiration_time = std::mktime(&tm);
               std::time_t current_time = std::chrono::system_clock::to_time_t(std::chrono::system_clock::now());
-              if (expiration_time <= current_time) {
+              if (expiration_time <= current_time) {   //数据过期
                 //std::cerr << "notfound_mem" << std::endl;
                 *s = Status::NotFound(Slice());
                 value->assign(v.data(), 0);
               }
-              else
+              else  //数据未过期
               {
                 value->assign(v.data(), v.size()-19);
               }
               return true;
             }
-          } else {
+          } else {  //时间戳信息不存在
             value->assign(v.data(), v.size());
             return true;
           }