diff --git a/db/db_impl.cc b/db/db_impl.cc
index 5814727..b43e94d 100644
--- a/db/db_impl.cc
+++ b/db/db_impl.cc
@@ -598,6 +598,7 @@ void DBImpl::CompactRange(const Slice* begin, const Slice* end) {
   for (int level = 0; level < max_level_with_files; level++) {
     TEST_CompactRange(level, begin, end);
   }
+  TEST_CompactRange(max_level_with_files, begin, end);
 }
 
 void DBImpl::TEST_CompactRange(int level, const Slice* begin,
@@ -756,7 +757,7 @@ void DBImpl::BackgroundCompaction() {
         status.ToString().c_str(), versions_->LevelSummary(&tmp));
   } else {
     CompactionState* compact = new CompactionState(c);
-    status = DoCompactionWork(compact);
+    status = DoCompactionWork(compact);//
     if (!status.ok()) {
       RecordBackgroundError(status);
     }
@@ -917,7 +918,6 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
   }
 
   Iterator* input = versions_->MakeInputIterator(compact->compaction);
-
   // Release mutex while we're actually doing the compaction work
   mutex_.Unlock();
 
@@ -949,7 +949,7 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
         break;
       }
     }
-
+    auto a = DecodeFixed64(input->value().data() + input->value().size() - kTSLength);
     // Handle key/value, add to state, etc.
     bool drop = false;
     if (!ParseInternalKey(key, &ikey)) {
@@ -981,6 +981,9 @@ Status DBImpl::DoCompactionWork(CompactionState* compact) {
         //     few iterations of this loop (by rule (A) above).
         // Therefore this deletion marker is obsolete and can be dropped.
         drop = true;
+      }else if(DecodeFixed64(input->value().data() + input->value().size() - kTSLength) < env_->NowMicros()){
+
+        drop = true;
       }
 
       last_sequence_for_key = ikey.sequence;
@@ -1228,7 +1231,7 @@ Status DBImpl::Put(const WriteOptions& options, const Slice& key,
   std::string val_with_ts;
   val_with_ts.reserve(value.size() + kTSLength);
   char ts_string[kTSLength];
-  TIMESTAMP expiration_time = this->env_->GetCurrentTime() + ttl * 1000;
+  TIMESTAMP expiration_time = this->env_->NowMicros() + ttl * 1000000;
   EncodeFixed64(ts_string,expiration_time);
   //assert(sizeof(expiration_time) == sizeof(TIMESTAMP ));
   // 追加原始 value 到 val_with_ts
@@ -1577,7 +1580,7 @@ uint64_t DBImpl::GetTS(std::string* val) {
 }
 Status DBImpl::CheckIsExpire(std::string* value) {
   //debug 用
-  auto a = env_->GetCurrentTime();
+  auto a = env_->NowMicros();
   auto b = GetTS(value);
 //  std::cout<<"get current time"<<a<<std::endl;
 //  std::cout << "get ts from val"<<b<<std::endl;
diff --git a/db/version_set.cc b/db/version_set.cc
index 4e37bf9..01bafca 100644
--- a/db/version_set.cc
+++ b/db/version_set.cc
@@ -138,7 +138,7 @@ bool SomeFileOverlapsRange(const InternalKeyComparator& icmp,
     return false;
   }
 
-  // Binary search over file list
+  // Binary search over file list, 保证SSTable有序
   uint32_t index = 0;
   if (smallest_user_key != nullptr) {
     // Find the earliest possible internal key for smallest_user_key
@@ -1386,7 +1386,7 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
   const int level = c->level();
   InternalKey smallest, largest;
 
-  AddBoundaryInputs(icmp_, current_->files_[level], &c->inputs_[0]);
+  AddBoundaryInputs(icmp_, current_->files_[level], &c->inputs_[0]);//增加边界值,userkey相等的情况
   GetRange(c->inputs_[0], &smallest, &largest);
 
   current_->GetOverlappingInputs(level + 1, &smallest, &largest,
@@ -1444,11 +1444,11 @@ void VersionSet::SetupOtherInputs(Compaction* c) {
   compact_pointer_[level] = largest.Encode().ToString();
   c->edit_.SetCompactPointer(level, largest);
 }
-
+//得到基于当前level的所涉及的需要compact的文件,(level0可能会涉及到level1等)
 Compaction* VersionSet::CompactRange(int level, const InternalKey* begin,
                                      const InternalKey* end) {
   std::vector<FileMetaData*> inputs;
-  current_->GetOverlappingInputs(level, begin, end, &inputs);
+  current_->GetOverlappingInputs(level, begin, end, &inputs);//得到一层的input
   if (inputs.empty()) {
     return nullptr;
   }
diff --git a/test/simple_test.cc b/test/simple_test.cc
index ec2edfa..3de1f3b 100644
--- a/test/simple_test.cc
+++ b/test/simple_test.cc
@@ -113,7 +113,7 @@ int main() {
   std::string key = std::to_string(key_);
   std::string value(1, 'a');
   db->Put(writeOptions, key, value, ttl);
-  std::cout << "time to alive" << ttl << std::endl;
+  //std::cout << "time to alive" << ttl << std::endl;
 
   ReadOptions readOptions;
   std::string value_read;
diff --git a/test/ttl_test.cc b/test/ttl_test.cc
index 438074b..3686336 100644
--- a/test/ttl_test.cc
+++ b/test/ttl_test.cc
@@ -39,7 +39,7 @@ void GetData(DB *db, int size = (1 << 30)) {
     db->Get(readOptions, key, &value);
   }
 }
-
+//
 TEST(TestTTL, ReadTTL) {
   DB *db;
   if(OpenDB("testdb", &db).ok() == false) {
@@ -100,7 +100,7 @@ TEST(TestTTL, CompactionTTL) {
   ranges2[0] = leveldb::Range("-", "A");
   uint64_t sizes2[1];
   db->GetApproximateSizes(ranges2, 1, sizes2);
-  ASSERT_EQ(sizes[0], 0);
+  ASSERT_EQ(sizes2[0], 0);
 }