diff --git a/src/observer/util/comparator.cpp b/deps/common/lang/comparator.cpp
similarity index 98%
rename from src/observer/util/comparator.cpp
rename to deps/common/lang/comparator.cpp
index 3a5712cf13dc4b4561db17e63991064aeda0b95c..b23d5753fafef07cd7ac8543edc78cc71df843ec 100644
--- a/src/observer/util/comparator.cpp
+++ b/deps/common/lang/comparator.cpp
@@ -16,6 +16,9 @@ See the Mulan PSL v2 for more details. */
 #include <algorithm>
 #include "common/defs.h"
 
+namespace common {
+
+
 int compare_int(void *arg1, void *arg2)
 {
   int v1 = *(int *)arg1;
@@ -56,3 +59,5 @@ int compare_string(void *arg1, int arg1_max_length, void *arg2, int arg2_max_len
   }
   return 0;
 }
+
+}
\ No newline at end of file
diff --git a/src/observer/util/comparator.h b/deps/common/lang/comparator.h
similarity index 97%
rename from src/observer/util/comparator.h
rename to deps/common/lang/comparator.h
index 18ab99fddd08874d6e59d9b615501b4be78fcd13..35e0cc9b22f3df2f670d33f08bb97cd68b919ef0 100644
--- a/src/observer/util/comparator.h
+++ b/deps/common/lang/comparator.h
@@ -14,6 +14,11 @@ See the Mulan PSL v2 for more details. */
 
 #pragma once
 
+namespace common {
+
+
 int compare_int(void *arg1, void *arg2);
 int compare_float(void *arg1, void *arg2);
 int compare_string(void *arg1, int arg1_max_length, void *arg2, int arg2_max_length);
+
+}
\ No newline at end of file
diff --git a/deps/common/lang/string.cpp b/deps/common/lang/string.cpp
index 79f044c020be4b4c91816d382450f2cdccf5dab8..ae0e38d26bd7b8aab96b2dfaa06f89cfaeea4254 100644
--- a/deps/common/lang/string.cpp
+++ b/deps/common/lang/string.cpp
@@ -265,4 +265,23 @@ char *substr(const char *s, int n1, int n2)
   return sp;
 }
 
+/**
+ * double to string
+ * @param v
+ * @return
+ */
+std::string double_to_str(double v)
+{
+  char buf[256];
+  snprintf(buf, sizeof(buf), "%.2f", v);
+  size_t len = strlen(buf);
+  while (buf[len - 1] == '0') {
+    len--;
+  }
+  if (buf[len - 1] == '.') {
+    len--;
+  }
+
+  return std::string(buf, len);
+}
 }  // namespace common
diff --git a/deps/common/lang/string.h b/deps/common/lang/string.h
index 446d3b515c1650b2f2a37e8a0e6f647737a532d9..bbf8235dbf1e85ba4e1fbe8f7f7ca6c113f25fb3 100644
--- a/deps/common/lang/string.h
+++ b/deps/common/lang/string.h
@@ -112,6 +112,13 @@ bool str_to_val(const std::string &str, T &val, std::ios_base &(*radix)(std::ios
 template <class T>
 void val_to_str(const T &val, std::string &str, std::ios_base &(*radix)(std::ios_base &) = std::dec);
 
+/**
+ * Double to string
+ * @param v
+ * @return
+ */
+std::string double_to_str(double v);
+
 bool is_blank(const char *s);
 
 /**
diff --git a/src/observer/sql/expr/tuple_cell.cpp b/src/observer/sql/expr/tuple_cell.cpp
index bfd5484e8af6fd8beb04646fe19e8af891bf635b..25f5dc4db71b9f25653eeaebabefd4b0435e6aee 100644
--- a/src/observer/sql/expr/tuple_cell.cpp
+++ b/src/observer/sql/expr/tuple_cell.cpp
@@ -16,8 +16,8 @@ See the Mulan PSL v2 for more details. */
 #include "sql/expr/tuple_cell.h"
 #include "storage/common/field.h"
 #include "common/log/log.h"
-#include "util/comparator.h"
-#include "util/util.h"
+#include "common/lang/comparator.h"
+#include "common/lang/string.h"
 
 TupleCellSpec::TupleCellSpec(const char *table_name, const char *field_name, const char *alias)
 {
@@ -140,7 +140,7 @@ void TupleCell::to_string(std::ostream &os) const
       os << num_value_.int_value_;
     } break;
     case FLOATS: {
-      os << double2string(num_value_.float_value_);
+      os << common::double_to_str(num_value_.float_value_);
     } break;
     case BOOLEANS: {
       os << num_value_.bool_value_;
@@ -159,19 +159,19 @@ int TupleCell::compare(const TupleCell &other) const
   if (this->attr_type_ == other.attr_type_) {
     switch (this->attr_type_) {
       case INTS: {
-        return compare_int((void *)&this->num_value_.int_value_, (void *)&other.num_value_.int_value_);
+        return common::compare_int((void *)&this->num_value_.int_value_, (void *)&other.num_value_.int_value_);
       } break;
       case FLOATS: {
-        return compare_float((void *)&this->num_value_.float_value_, (void *)&other.num_value_.float_value_);
+        return common::compare_float((void *)&this->num_value_.float_value_, (void *)&other.num_value_.float_value_);
       } break;
       case CHARS: {
-        return compare_string((void *)this->str_value_.c_str(),
+        return common::compare_string((void *)this->str_value_.c_str(),
             this->str_value_.length(),
             (void *)other.str_value_.c_str(),
             other.str_value_.length());
       } break;
       case BOOLEANS: {
-        return compare_int((void *)&this->num_value_.bool_value_, (void *)&other.num_value_.bool_value_);
+        return common::compare_int((void *)&this->num_value_.bool_value_, (void *)&other.num_value_.bool_value_);
       }
       default: {
         LOG_WARN("unsupported type: %d", this->attr_type_);
@@ -179,10 +179,10 @@ int TupleCell::compare(const TupleCell &other) const
     }
   } else if (this->attr_type_ == INTS && other.attr_type_ == FLOATS) {
     float this_data = this->num_value_.int_value_;
-    return compare_float((void *)&this_data, (void *)&other.num_value_.float_value_);
+    return common::compare_float((void *)&this_data, (void *)&other.num_value_.float_value_);
   } else if (this->attr_type_ == FLOATS && other.attr_type_ == INTS) {
     float other_data = other.num_value_.int_value_;
-    return compare_float((void *)&this->num_value_.float_value_, (void *)&other_data);
+    return common::compare_float((void *)&this->num_value_.float_value_, (void *)&other_data);
   }
   LOG_WARN("not supported");
   return -1;  // TODO return rc?
diff --git a/src/observer/storage/index/bplus_tree.h b/src/observer/storage/index/bplus_tree.h
index 7631b5eda0b09b4edc244cba1c20e9bc94bba43e..68b89d88b79aa03197fb461f3cfa64d8957877d5 100644
--- a/src/observer/storage/index/bplus_tree.h
+++ b/src/observer/storage/index/bplus_tree.h
@@ -24,7 +24,7 @@ See the Mulan PSL v2 for more details. */
 #include "storage/record/record_manager.h"
 #include "storage/default/disk_buffer_pool.h"
 #include "sql/parser/parse_defs.h"
-#include "util/comparator.h"
+#include "common/lang/comparator.h"
 
 #define EMPTY_RID_PAGE_NUM -1
 #define EMPTY_RID_SLOT_NUM -1
@@ -46,13 +46,13 @@ public:
   {
     switch (attr_type_) {
       case INTS: {
-        return compare_int((void *)v1, (void *)v2);
+        return common::compare_int((void *)v1, (void *)v2);
       } break;
       case FLOATS: {
-        return compare_float((void *)v1, (void *)v2);
+        return common::compare_float((void *)v1, (void *)v2);
       }
       case CHARS: {
-        return compare_string((void *)v1, attr_length_, (void *)v2, attr_length_);
+        return common::compare_string((void *)v1, attr_length_, (void *)v2, attr_length_);
       }
       default: {
         LOG_ERROR("unknown attr type. %d", attr_type_);
diff --git a/src/observer/util/util.cpp b/src/observer/util/util.cpp
deleted file mode 100644
index 83465c413818174498e77b3268856553463191a1..0000000000000000000000000000000000000000
--- a/src/observer/util/util.cpp
+++ /dev/null
@@ -1,31 +0,0 @@
-/* Copyright (c) 2021 Xie Meiyi(xiemeiyi@hust.edu.cn) and OceanBase and/or its affiliates. All rights reserved.
-miniob is licensed under Mulan PSL v2.
-You can use this software according to the terms and conditions of the Mulan PSL v2.
-You may obtain a copy of Mulan PSL v2 at:
-         http://license.coscl.org.cn/MulanPSL2
-THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
-EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
-MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
-See the Mulan PSL v2 for more details. */
-
-//
-// Created by wangyunlai on 2022/9/28
-//
-
-#include <string.h>
-#include "util/util.h"
-
-std::string double2string(double v)
-{
-  char buf[256];
-  snprintf(buf, sizeof(buf), "%.2f", v);
-  size_t len = strlen(buf);
-  while (buf[len - 1] == '0') {
-    len--;
-  }
-  if (buf[len - 1] == '.') {
-    len--;
-  }
-
-  return std::string(buf, len);
-}
diff --git a/src/observer/util/util.h b/src/observer/util/util.h
deleted file mode 100644
index c7db5605eae62e9e15902fc30f99b33531257bd1..0000000000000000000000000000000000000000
--- a/src/observer/util/util.h
+++ /dev/null
@@ -1,19 +0,0 @@
-/* Copyright (c) 2021 Xie Meiyi(xiemeiyi@hust.edu.cn) and OceanBase and/or its affiliates. All rights reserved.
-miniob is licensed under Mulan PSL v2.
-You can use this software according to the terms and conditions of the Mulan PSL v2.
-You may obtain a copy of Mulan PSL v2 at:
-         http://license.coscl.org.cn/MulanPSL2
-THIS SOFTWARE IS PROVIDED ON AN "AS IS" BASIS, WITHOUT WARRANTIES OF ANY KIND,
-EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO NON-INFRINGEMENT,
-MERCHANTABILITY OR FIT FOR A PARTICULAR PURPOSE.
-See the Mulan PSL v2 for more details. */
-
-//
-// Created by wangyunlai on 2022/9/28
-//
-
-#pragma once
-
-#include <string>
-
-std::string double2string(double v);