文件元数据增加deadtime的范围，并根据范围对文件在合并时候进行清除，可以解决手动合并不完全的情况

db/db_impl.cc

@@ -591,7 +591,7 @@ void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
       }
     }
   }
-  max_level_with_files = config::kNumLevels - 1; //TODO:强制合并所有level中的sst,但是这么做不是很优雅
+  // max_level_with_files = config::kNumLevels - 1; //TODO:强制合并所有level中的sst,但是这么做不是很优雅
   TEST_CompactMemTable();  // TODO(sanjay): Skip if memtable does not overlap
   for (int level = 0; level < max_level_with_files; level++) {
     TEST_CompactRange(level, begin, end);
@@ -706,6 +706,31 @@ void DBImpl::BackgroundCall() {
   background_work_finished_signal_.SignalAll();
 }
 
+bool DBImpl::RemoveExpireTable() {
+  bool remove = false;
+  VersionEdit edit;
+  time_t nowTime;
+  time(&nowTime);
+  Version *base = versions_->current();
+  base->Ref();
+  for(int level = 0; level < config::kNumLevels; level ++) {
+    const std::vector<FileMetaData*> &files = versions_->current()->Files(level);
+    for(auto meta:files) {
+      if(meta->largest_deadtime < nowTime) {
+        remove = true;
+        edit.RemoveFile(level,meta->number);
+        std::cout<<"remove file : "<<meta->number<<" from level : "<<level<<std::endl;
+      }
+    }
+  }
+  if(remove) {
+    versions_->LogAndApply(&edit,&mutex_);
+    RemoveObsoleteFiles();
+  }
+  base->Unref();
+  return remove;
+}
+
 void DBImpl::BackgroundCompaction() {
   mutex_.AssertHeld();
 
@@ -714,6 +739,10 @@ void DBImpl::BackgroundCompaction() {
     return;
   }
 
+  if(RemoveExpireTable()) {
+    return;
+  }
+
   Compaction* c;
   bool is_manual = (manual_compaction_ != nullptr);
   InternalKey manual_end;

db/db_impl.h

@@ -145,6 +145,7 @@ class DBImpl : public DB {
       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
   Status DoCompactionWork(CompactionState* compact)
       EXCLUSIVE_LOCKS_REQUIRED(mutex_);
+  bool RemoveExpireTable(); //if remove some table thne return true otherwise return false
 
   Status OpenCompactionOutputFile(CompactionState* compact);
   Status FinishCompactionOutputFile(CompactionState* compact, Iterator* input);

db/version_set.h

@@ -111,6 +111,8 @@ class Version {
 
   int NumFiles(int level) const { return files_[level].size(); }
 
+  const std::vector<FileMetaData*>& Files(int level) const {return files_[level]; }
+
   // Return a human readable string that describes this version's contents.
   std::string DebugString() const;