diff --git a/src/storage/blocksstable/encoding/ob_column_equal_encoder.h b/src/storage/blocksstable/encoding/ob_column_equal_encoder.h
index 036190a2a..ab3085296 100644
--- a/src/storage/blocksstable/encoding/ob_column_equal_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_column_equal_encoder.h
@@ -72,6 +72,7 @@ public:
     UNUSED(buf_writer);
     return common::OB_NOT_SUPPORTED;
   }
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(ref_col_idx));
 private:
   OB_INLINE int is_datum_equal(
       const common::ObDatum &left,
diff --git a/src/storage/blocksstable/encoding/ob_const_encoder.h b/src/storage/blocksstable/encoding/ob_const_encoder.h
index cdb49b642..6cadb382f 100644
--- a/src/storage/blocksstable/encoding/ob_const_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_const_encoder.h
@@ -72,6 +72,7 @@ public:
 
   virtual void reuse() override ;
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(count), K_(row_id_byte), KPC_(const_meta_header), K_(dict_encoder));
 private:
   int store_meta_without_dict(ObBufferWriter &buf_writer);
   int get_cell_len(const common::ObDatum &datum, int64_t &length) const;
diff --git a/src/storage/blocksstable/encoding/ob_dict_encoder.h b/src/storage/blocksstable/encoding/ob_dict_encoder.h
index 5cf109958..c771b4869 100644
--- a/src/storage/blocksstable/encoding/ob_dict_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_dict_encoder.h
@@ -121,6 +121,8 @@ public:
 
   virtual ObColumnHeader::Type get_type() const override { return type_; }
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(type_store_size), K_(dict_fix_data_size),
+      K_(var_data_size), K_(dict_index_byte), K_(max_integer), KPC_(dict_meta_header), K_(count), K_(need_sort));
 private:
   int build_dict();
   int store_dict(const common::ObDatum &datum, char *buf, int64_t &len);
diff --git a/src/storage/blocksstable/encoding/ob_hex_string_encoder.h b/src/storage/blocksstable/encoding/ob_hex_string_encoder.h
index 0b50effd0..9cf48327b 100644
--- a/src/storage/blocksstable/encoding/ob_hex_string_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_hex_string_encoder.h
@@ -175,7 +175,8 @@ public:
 
   virtual void reuse() override;
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
-
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(min_string_size), K_(max_string_size),
+      K_(sum_size), K_(null_cnt), K_(nope_cnt), KPC_(header));
 private:
   struct ColumnStoreFiller;
 
diff --git a/src/storage/blocksstable/encoding/ob_integer_base_diff_encoder.h b/src/storage/blocksstable/encoding/ob_integer_base_diff_encoder.h
index f4609cd19..037aa7c61 100644
--- a/src/storage/blocksstable/encoding/ob_integer_base_diff_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_integer_base_diff_encoder.h
@@ -63,6 +63,7 @@ public:
   virtual int64_t calc_size() const override;
   virtual ObColumnHeader::Type get_type() const { return type_; }
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(type_store_size), KPC_(header));
 private:
   class ObIIntegerData
   {
diff --git a/src/storage/blocksstable/encoding/ob_inter_column_substring_encoder.h b/src/storage/blocksstable/encoding/ob_inter_column_substring_encoder.h
index 8f292ef7e..3e839e44e 100644
--- a/src/storage/blocksstable/encoding/ob_inter_column_substring_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_inter_column_substring_encoder.h
@@ -92,6 +92,8 @@ public:
   virtual int64_t get_ref_col_idx() const override;
   virtual void reuse() override;
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(ref_col_idx), KPC_(ref_ctx),
+      K_(same_start_pos), K_(fix_data_size), K_(start_pos_byte), K_(val_len_byte));
 
 private:
   // return:
diff --git a/src/storage/blocksstable/encoding/ob_micro_block_encoder.cpp b/src/storage/blocksstable/encoding/ob_micro_block_encoder.cpp
index 1b4c62154..390bd4543 100644
--- a/src/storage/blocksstable/encoding/ob_micro_block_encoder.cpp
+++ b/src/storage/blocksstable/encoding/ob_micro_block_encoder.cpp
@@ -342,7 +342,8 @@ void ObMicroBlockEncoder::print_micro_block_encoder_status() const
 {
   FLOG_INFO("Build micro block failed, print encoder status: ", K_(ctx),
     K_(estimate_size), K_(estimate_size_limit), K_(header_size),
-      K_(expand_pct), K_(string_col_cnt), K_(estimate_base_store_size), K_(length));
+      K_(expand_pct), K_(string_col_cnt), K_(estimate_base_store_size), K_(length),
+      K(get_row_count()));
   int64_t idx = 0;
   FOREACH(e, encoders_) {
     FLOG_INFO("Print column encoder: ", K(idx), KPC(*e));
diff --git a/src/storage/blocksstable/encoding/ob_raw_encoder.h b/src/storage/blocksstable/encoding/ob_raw_encoder.h
index e7510fdc7..3e9e91f56 100644
--- a/src/storage/blocksstable/encoding/ob_raw_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_raw_encoder.h
@@ -64,6 +64,8 @@ public:
   virtual ObColumnHeader::Type get_type() const override { return type_; }
 
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(type_store_size), K_(null_cnt),
+      K_(nope_cnt), K_(fix_data_size), K_(max_integer), K_(var_data_size));
 
 private:
   struct DatumDataSetter;
diff --git a/src/storage/blocksstable/encoding/ob_rle_encoder.h b/src/storage/blocksstable/encoding/ob_rle_encoder.h
index 6feaefc21..9dfe4ead3 100644
--- a/src/storage/blocksstable/encoding/ob_rle_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_rle_encoder.h
@@ -73,6 +73,8 @@ public:
   virtual int64_t calc_size() const override;
   virtual ObColumnHeader::Type get_type() const override { return type_; }
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(count), K_(row_id_byte),
+      K_(ref_byte), KPC_(rle_meta_header), K_(dict_encoder));
 private:
   int64_t count_;
   int64_t row_id_byte_;
diff --git a/src/storage/blocksstable/encoding/ob_string_diff_encoder.cpp b/src/storage/blocksstable/encoding/ob_string_diff_encoder.cpp
index 2e992501b..c7e82e95d 100644
--- a/src/storage/blocksstable/encoding/ob_string_diff_encoder.cpp
+++ b/src/storage/blocksstable/encoding/ob_string_diff_encoder.cpp
@@ -366,7 +366,17 @@ int ObStringDiffEncoder::get_var_length(const int64_t row_id, int64_t &length)
     ret = OB_INVALID_ARGUMENT;
     LOG_WARN("invalid argument", K(ret), K(row_id));
   } else {
-    length = row_store_size_;
+    const int64_t &data_version = ctx_->encoding_ctx_->major_working_cluster_version_;
+    // For version 4.x, fix string diff var-length encoding overflow on versions:
+    // from 4.2.5 bp2 to 4.3.0, and all versions after 4.3.5
+    const bool enable_var_length_fix = (data_version > DATA_VERSION_4_3_5_0)
+        || (data_version >= MOCK_DATA_VERSION_4_2_5_2 && data_version < DATA_VERSION_4_3_0_0);
+    const ObDatum &datum = rows_->at(row_id).get_datum(column_index_);
+    if (enable_var_length_fix && (datum.is_null() || datum.is_nop())) {
+      length = 0;
+    } else {
+      length = row_store_size_;
+    }
   }
   return ret;
 }
diff --git a/src/storage/blocksstable/encoding/ob_string_diff_encoder.h b/src/storage/blocksstable/encoding/ob_string_diff_encoder.h
index 8dcb2d56a..f2191353f 100644
--- a/src/storage/blocksstable/encoding/ob_string_diff_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_string_diff_encoder.h
@@ -130,6 +130,8 @@ public:
   virtual int64_t calc_size() const override;
   virtual ObColumnHeader::Type get_type() const override { return type_; }
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, K_(string_size), K_(common_size), K_(row_store_size),
+      K_(null_cnt), K_(nope_cnt), KPC_(header), K_(last_change_diff_row_id));
 private:
   int traverse_cell(
       char *&data,
diff --git a/src/storage/blocksstable/encoding/ob_string_prefix_encoder.h b/src/storage/blocksstable/encoding/ob_string_prefix_encoder.h
index 1d443bcb5..efe7497ba 100644
--- a/src/storage/blocksstable/encoding/ob_string_prefix_encoder.h
+++ b/src/storage/blocksstable/encoding/ob_string_prefix_encoder.h
@@ -132,6 +132,8 @@ public:
   virtual int64_t calc_size() const override;
   virtual ObColumnHeader::Type get_type() const override { return type_; }
   virtual int store_fix_data(ObBufferWriter &buf_writer) override;
+  INHERIT_TO_STRING_KV("ObIColumnEncoder", ObIColumnEncoder, KPC_(meta_header), K_(prefix_count),
+      K_(prefix_index_byte), K_(prefix_length), K_(calc_size));
 private:
   ObStringPrefixMetaHeader *meta_header_;
   int64_t prefix_count_;
diff --git a/unittest/storage/blocksstable/encoding/test_micro_block_encoder.cpp b/unittest/storage/blocksstable/encoding/test_micro_block_encoder.cpp
index 1bbf1a8a9..513f20f2e 100644
--- a/unittest/storage/blocksstable/encoding/test_micro_block_encoder.cpp
+++ b/unittest/storage/blocksstable/encoding/test_micro_block_encoder.cpp
@@ -332,6 +332,95 @@ TEST_F(TestColumnEqualExceptionList, test_column_equal_ext_offset_overflow)
 
 }
 
+static ObObjType test_string_diff[2] = {ObIntType, ObVarcharType};
+class TestStringDiffNullLength : public TestIColumnEncoder
+{
+public:
+  TestStringDiffNullLength() {}
+  virtual ~TestStringDiffNullLength() {}
+  virtual void SetUp();
+  virtual void TearDown();
+};
+
+void TestStringDiffNullLength::SetUp()
+{
+  rowkey_cnt_ = 1;
+  column_cnt_ = 2;
+  col_types_ = reinterpret_cast<ObObjType *>(allocator_.alloc(sizeof(ObObjType) * column_cnt_));
+  ASSERT_NE(nullptr, col_types_);
+  for (int64_t i = 0; i < column_cnt_; ++i) {
+    col_types_[i] = test_string_diff[i];
+  }
+  TestIColumnEncoder::SetUp();
+}
+
+void TestStringDiffNullLength::TearDown()
+{
+  TestIColumnEncoder::TearDown();
+  allocator_.free(col_types_);
+}
+
+TEST_F(TestStringDiffNullLength, test_string_diff_null_length)
+{
+  int64_t column_encoding_array[2] =
+      {ObColumnHeader::Type::RAW,
+       ObColumnHeader::Type::STRING_DIFF};
+  ctx_.column_encodings_ = column_encoding_array;
+  ctx_.micro_block_size_ = 1 << 20; // 1M
+  ctx_.major_working_cluster_version_ = DATA_VERSION_4_3_5_1;
+  ObMicroBlockEncoder encoder;
+  encoder.data_buffer_.allocator_.set_tenant_id(500);
+  encoder.row_buf_holder_.allocator_.set_tenant_id(500);
+  ASSERT_EQ(OB_SUCCESS, encoder.init(ctx_));
+
+  ObDatumRow row;
+  ASSERT_EQ(OB_SUCCESS, row.init(allocator_, 2));
+  const char *str1 = "this is a meaningless string for a test case to verify fixed string diff encoding";
+  const char *str2 = "this is 7777777777777777777777777777777777777777777777777777777777777777 encoding";
+  const char *str3 = "this is 8888888888888888888888888888888888888888888888888888888888888888 encoding";
+  row.storage_datums_[0].set_int(0);
+  row.storage_datums_[1].set_string(ObString(str1));
+  const int64_t single_str_len = row.storage_datums_[1].len_;
+  ASSERT_EQ(OB_SUCCESS, encoder.append_row(row));
+  row.storage_datums_[0].set_int(1);
+  row.storage_datums_[1].set_string(ObString(str2));
+  ASSERT_EQ(OB_SUCCESS, encoder.append_row(row));
+  row.storage_datums_[0].set_int(2);
+  row.storage_datums_[1].set_string(ObString(str3));
+  ASSERT_EQ(OB_SUCCESS, encoder.append_row(row));
+  for (int64_t i = 0; i < 52400; ++i) {
+    row.storage_datums_[0].set_int(i + 3);
+    row.storage_datums_[1].set_null();
+    ASSERT_EQ(OB_SUCCESS, encoder.append_row(row));
+  }
+
+  char *buf = nullptr;
+  int64_t size = 0;
+  ASSERT_EQ(OB_SUCCESS, encoder.build_block(buf, size));
+
+  LOG_INFO("show sizes", K(encoder.length_), K(size));
+
+  ObMicroBlockData micro_data(buf, size);
+  ObMicroBlockDecoder decoder;
+  ObDatumRow read_row;
+  ASSERT_EQ(OB_SUCCESS, read_row.init(2));
+  ASSERT_EQ(OB_SUCCESS, decoder.init(micro_data, nullptr));
+  ASSERT_EQ(OB_SUCCESS, decoder.get_row(0, read_row));
+  const ObString &read_string1 = read_row.storage_datums_[1].get_string();
+  ASSERT_EQ(0, MEMCMP(str1, read_string1.ptr(), read_string1.length()));
+  ASSERT_EQ(OB_SUCCESS, decoder.get_row(1, read_row));
+  const ObString &read_string2 = read_row.storage_datums_[1].get_string();
+  ASSERT_EQ(0, MEMCMP(str2, read_string2.ptr(), read_string2.length()));
+  ASSERT_EQ(OB_SUCCESS, decoder.get_row(2, read_row));
+  const ObString &read_string3 = read_row.storage_datums_[1].get_string();
+  ASSERT_EQ(0, MEMCMP(str3, read_string3.ptr(), read_string3.length()));
+  for (int64_t i = 0; i < 52400; ++i) {
+    ASSERT_EQ(OB_SUCCESS, decoder.get_row(i + 3, read_row));
+    ASSERT_TRUE(read_row.storage_datums_[1].is_null());
+  }
+
+}
+
 class TestEncodingRowBufHolder : public ::testing::Test
 {
 public: