diff --git a/storage/tianmu/data/pack_str.cpp b/storage/tianmu/data/pack_str.cpp
index 2eacafe6c..d6b636d88 100644
--- a/storage/tianmu/data/pack_str.cpp
+++ b/storage/tianmu/data/pack_str.cpp
@@ -205,7 +205,6 @@ void PackStr::UpdateValue(size_t locationInPack, const Value &v) {
       dpn_->max_i = -1;
     }
 
-    // ASSERT(v.HasValue(), col_share_->DataFile() + " locationInPack: " + std::to_string(locationInPack));
     UnsetNull(locationInPack);
     dpn_->numOfNulls--;
     auto &str = v.GetString();
@@ -227,10 +226,13 @@ void PackStr::UpdateValue(size_t locationInPack, const Value &v) {
       SetPtrSize(locationInPack, nullptr, 0);
       SetNull(locationInPack);
       dpn_->numOfNulls++;
+      if(dpn_->NullOnly()){
+        data_.sum_len = 0;
+      }
     } else {
       // update non-null to another nonull
       auto vsize = GetValueBinary(locationInPack).size();
-      ASSERT(data_.sum_len >= vsize);
+      ASSERT(data_.sum_len >= vsize, col_share_->DataFile() + ", data_.sum_len:" + std::to_string(data_.sum_len) + ", vsize:"+std::to_string(vsize));
       data_.sum_len -= vsize;
       auto &str = v.GetString();
       if (str.size() <= vsize) {
@@ -260,6 +262,9 @@ void PackStr::DeleteByRow(size_t locationInPack) {
     SetPtrSize(locationInPack, nullptr, 0);
     SetNull(locationInPack);
     dpn_->numOfNulls++;
+    if(dpn_->NullOnly()){
+      data_.sum_len = 0;
+    }
   }
   SetDeleted(locationInPack);
   dpn_->numOfDeleted++;
@@ -381,7 +386,7 @@ std::pair<PackStr::UniquePtr, size_t> PackStr::Compress() {
         reinterpret_cast<uint *>(alloc(comp_len_buf_size / 4 * sizeof(uint), mm::BLOCK_TYPE::BLOCK_TEMPORARY)), *this);
     uint tmp_comp_len_buf_size = comp_len_buf_size - 8;
     compress::NumCompressor<uint> nc;
-    CprsErr res = nc.Compress(reinterpret_cast<char *>(comp_len_buf.get() + sizeof(ushort)), tmp_comp_len_buf_size,
+    CprsErr res = nc.Compress(reinterpret_cast<char *>(comp_len_buf.get() + 2), tmp_comp_len_buf_size,
                               nc_buffer.get(), onn, maxv);
     if (res != CprsErr::CPRS_SUCCESS) {
       throw common::InternalException("Compression of lengths of values failed for column " +
@@ -409,7 +414,7 @@ std::pair<PackStr::UniquePtr, size_t> PackStr::Compress() {
 
   mm::MMGuard<char> comp_buf(reinterpret_cast<char *>(alloc(dlen, mm::BLOCK_TYPE::BLOCK_TEMPORARY)), *this);
 
-  if (data_.sum_len) {
+  if (data_.sum_len > 0) {
     int objs = (dpn_->numOfRecords - dpn_->numOfNulls) - zlo;
 
     mm::MMGuard<char *> tmp_index(
@@ -559,7 +564,7 @@ void PackStr::Save() {
     SaveUncompressed(&f);
   }
 
-  ASSERT(f.Tell() == off_t(dpn_->dataAddress + dpn_->dataLength),
+  ASSERT(f.Tell() == off_t(dpn_->dataAddress + dpn_->dataLength), col_share_->DataFile() + ", " +
          std::to_string(dpn_->dataAddress) + ":" + std::to_string(dpn_->dataLength) + "/" + std::to_string(f.Tell()));
   dpn_->synced = true;
 }
@@ -568,8 +573,10 @@ void PackStr::SaveUncompressed(system::Stream *f) {
   f->WriteExact(nulls_ptr_.get(), bitmap_size_);
   f->WriteExact(deletes_ptr_.get(), bitmap_size_);
   f->WriteExact(data_.lens, (data_.len_mode * (1 << col_share_->pss)));
-  if (data_.v.empty())
+  if (data_.v.empty() || dpn_->NullOnly()){
     return;
+  }
+
 
   std::unique_ptr<char[]> buff(new char[data_.sum_len]);
   char *ptr = buff.get();
@@ -586,7 +593,7 @@ void PackStr::SaveUncompressed(system::Stream *f) {
 }
 
 void PackStr::LoadCompressed(system::Stream *f) {
-  ASSERT(IsModeCompressionApplied());
+  ASSERT(IsModeCompressionApplied() , "path:" + col_share_->DataFile());
 
   auto compressed_buf = alloc_ptr(dpn_->dataLength + 1, mm::BLOCK_TYPE::BLOCK_COMPRESSED);
   f->ReadExact(compressed_buf.get(), dpn_->dataLength);
@@ -619,7 +626,7 @@ void PackStr::LoadCompressed(system::Stream *f) {
   }
 
   if (dpn_->numOfDeleted > 0) {
-    uint delete_buf_size = 0;
+    ushort delete_buf_size = 0;
     delete_buf_size = (*reinterpret_cast<ushort *>(cur_buf));
     if (delete_buf_size > bitmap_size_)
       throw common::DatabaseException("Unexpected bytes found in data pack.");
@@ -628,7 +635,7 @@ void PackStr::LoadCompressed(system::Stream *f) {
     else {
       compress::BitstreamCompressor bsc;
       CprsErr res = bsc.Decompress(reinterpret_cast<char *>(deletes_ptr_.get()), delete_buf_size,
-                                   reinterpret_cast<char *>(cur_buf) + 2, dpn_->numOfRecords, dpn_->numOfDeleted);
+                                   reinterpret_cast<char *>(cur_buf) + sizeof(ushort), dpn_->numOfRecords, dpn_->numOfDeleted);
       if (res != CprsErr::CPRS_SUCCESS) {
         throw common::DatabaseException("Decompression of deletes failed for column " +
                                         std::to_string(pc_column(GetCoordinate().co.pack) + 1) + ", pack " +
@@ -646,7 +653,7 @@ void PackStr::LoadCompressed(system::Stream *f) {
     compress::NumCompressor<uint> nc;
     mm::MMGuard<uint> cn_ptr((uint *)alloc((1 << col_share_->pss) * sizeof(uint), mm::BLOCK_TYPE::BLOCK_TEMPORARY),
                              *this);
-    CprsErr res = nc.Decompress(cn_ptr.get(), reinterpret_cast<char *>(cur_buf + 8), comp_len_buf_size - 8,
+    CprsErr res = nc.Decompress(cn_ptr.get(), reinterpret_cast<char *>(cur_buf + sizeof(uint32_t)*2), comp_len_buf_size - 8,
                                 dpn_->numOfRecords - dpn_->numOfNulls, maxv);
     if (res != CprsErr::CPRS_SUCCESS) {
       std::stringstream msg_buf;
@@ -714,7 +721,7 @@ void PackStr::LoadCompressed(system::Stream *f) {
 }
 
 void PackStr::LoadCompressedTrie(system::Stream *f) {
-  ASSERT(IsModeCompressionApplied());
+  ASSERT(IsModeCompressionApplied() , "path:" + col_share_->DataFile());
   compressed_data_.reset(nullptr);
   compressed_data_ = alloc_ptr(dpn_->dataLength + 1, mm::BLOCK_TYPE::BLOCK_COMPRESSED);
   f->ReadExact(compressed_data_.get(), dpn_->dataLength);