diff --git a/src/observer/sql/expr/expression.h b/src/observer/sql/expr/expression.h
index c586bf2d2193d0c7c439dff6f2dea93481ccebca..59b1750d8173c7950ec6aa59084fe7bec9e5c3fc 100644
--- a/src/observer/sql/expr/expression.h
+++ b/src/observer/sql/expr/expression.h
@@ -14,6 +14,7 @@ See the Mulan PSL v2 for more details. */
 
 #pragma once
 
+#include <string.h>
 #include "storage/common/field.h"
 #include "sql/expr/tuple_cell.h"
 
@@ -79,7 +80,11 @@ class ValueExpr : public Expression
 public:
   ValueExpr() = default;
   ValueExpr(const Value &value) : tuple_cell_(value.type, (char *)value.data)
-  {}
+  {
+    if (value.type == CHARS) {
+      tuple_cell_.set_length(strlen((const char *)value.data));
+    }
+  }
 
   virtual ~ValueExpr() = default;
 
diff --git a/src/observer/sql/expr/tuple.h b/src/observer/sql/expr/tuple.h
index 07c33c793e17a61f9f2cd4bb1cf01ca90fc7f06c..7efed51faf976edab5419b983b6107732d5c6708 100644
--- a/src/observer/sql/expr/tuple.h
+++ b/src/observer/sql/expr/tuple.h
@@ -115,6 +115,7 @@ public:
     const FieldMeta *field_meta = field_expr->field().meta();
     cell.set_type(field_meta->type());
     cell.set_data(this->record_->data() + field_meta->offset());
+    cell.set_length(field_meta->len());
     return RC::SUCCESS;
   }
 
diff --git a/src/observer/sql/expr/tuple_cell.cpp b/src/observer/sql/expr/tuple_cell.cpp
index 9ccd3d393cb27aa0df6923d1b33df298216baf29..c878b31c632307da84b4bf3c28a0ff843d9f65fc 100644
--- a/src/observer/sql/expr/tuple_cell.cpp
+++ b/src/observer/sql/expr/tuple_cell.cpp
@@ -27,7 +27,7 @@ void TupleCell::to_string(std::ostream &os) const
     os << *(float *)data_;
   } break;
   case CHARS: {
-    for (int i = 0; i < 4; i++) { // the max length of CHARS is 4
+    for (int i = 0; i < length_; i++) {
       if (data_[i] == '\0') {
         break;
       }
@@ -46,7 +46,7 @@ int TupleCell::compare(const TupleCell &other) const
     switch (this->attr_type_) {
     case INTS: return compare_int(this->data_, other.data_);
     case FLOATS: return compare_float(this->data_, other.data_);
-    case CHARS: return compare_string(this->data_, other.data_, 4);
+    case CHARS: return compare_string(this->data_, this->length_, other.data_, other.length_);
     default: {
       LOG_WARN("unsupported type: %d", this->attr_type_);
     }
diff --git a/src/observer/sql/expr/tuple_cell.h b/src/observer/sql/expr/tuple_cell.h
index 89170f2ed28d17b325889a8bcf05aa5c85b6e9a6..faf39964c07549817c043aaa97c02146d91b67ac 100644
--- a/src/observer/sql/expr/tuple_cell.h
+++ b/src/observer/sql/expr/tuple_cell.h
@@ -31,6 +31,7 @@ public:
   {}
 
   void set_type(AttrType type) { this->attr_type_ = type; }
+  void set_length(int length) { this->length_ = length; }
   void set_data(char *data) { this->data_ = data; }
   void set_data(const char *data) { this->set_data(const_cast<char *>(data)); }
 
@@ -43,11 +44,15 @@ public:
     return data_;
   }
 
+  int length() const { return length_; }
+
   AttrType attr_type() const
   {
     return attr_type_;
   }
+
 private:
   AttrType attr_type_ = UNDEFINED;
+  int length_ = -1;
   char *data_ = nullptr; // real data. no need to move to field_meta.offset
 };
diff --git a/src/observer/sql/operator/index_scan_operator.cpp b/src/observer/sql/operator/index_scan_operator.cpp
index 1be1a3723a8cc48d6f7765022d7994fb7c038e9d..2aad13be19ab13d6068be1b765ce90d27478b09a 100644
--- a/src/observer/sql/operator/index_scan_operator.cpp
+++ b/src/observer/sql/operator/index_scan_operator.cpp
@@ -36,8 +36,8 @@ RC IndexScanOperator::open()
   }
 
   
-  IndexScanner *index_scanner = index_->create_scanner(left_cell_.data(), left_inclusive_,
-					       right_cell_.data(), right_inclusive_);
+  IndexScanner *index_scanner = index_->create_scanner(left_cell_.data(), left_cell_.length(), left_inclusive_,
+                                                       right_cell_.data(), right_cell_.length(), right_inclusive_);
   if (nullptr == index_scanner) {
     LOG_WARN("failed to create index scanner");
     return RC::INTERNAL;
diff --git a/src/observer/storage/common/condition_filter.h b/src/observer/storage/common/condition_filter.h
index 890195af05b586daafeaed3c7a0edb35b49f5f7f..e4b7f98fceb7682903d415535cdf951216904825 100644
--- a/src/observer/storage/common/condition_filter.h
+++ b/src/observer/storage/common/condition_filter.h
@@ -66,6 +66,8 @@ public:
     return comp_op_;
   }
 
+  AttrType attr_type() const { return attr_type_; }
+
 private:
   ConDesc left_;
   ConDesc right_;
diff --git a/src/observer/storage/common/table.cpp b/src/observer/storage/common/table.cpp
index 7ff43cab5cc255c2aa937b7805a392a3553a1d9f..f53be21701492c6603fef6ffc600187e02481364 100644
--- a/src/observer/storage/common/table.cpp
+++ b/src/observer/storage/common/table.cpp
@@ -326,7 +326,14 @@ RC Table::make_record(int value_num, const Value *values, char *&record_out)
   for (int i = 0; i < value_num; i++) {
     const FieldMeta *field = table_meta_.field(i + normal_field_start_index);
     const Value &value = values[i];
-    memcpy(record + field->offset(), value.data, field->len());
+    size_t copy_len = field->len();
+    if (field->type() == CHARS) {
+      const size_t data_len = strlen((const char *)value.data);
+      if (copy_len > data_len) {
+        copy_len = data_len + 1;
+      }
+    }
+    memcpy(record + field->offset(), value.data, copy_len);
   }
 
   record_out = record;
@@ -775,6 +782,8 @@ IndexScanner *Table::find_index_for_scan(const DefaultConditionFilter &filter)
 
   const char *left_key = nullptr;
   const char *right_key = nullptr;
+  int left_len = 4;
+  int right_len = 4;
   bool left_inclusive = false;
   bool right_inclusive = false;
   switch (filter.comp_op()) {
@@ -809,7 +818,12 @@ IndexScanner *Table::find_index_for_scan(const DefaultConditionFilter &filter)
     return nullptr;
   }
   }
-  return index->create_scanner(left_key, left_inclusive, right_key, right_inclusive);
+
+  if (filter.attr_type() == CHARS) {
+    left_len = left_key != nullptr ? strlen(left_key) : 0;
+    right_len = right_key != nullptr ? strlen(right_key) : 0;
+  }
+  return index->create_scanner(left_key, left_len, left_inclusive, right_key, right_len, right_inclusive);
 }
 
 IndexScanner *Table::find_index_for_scan(const ConditionFilter *filter)
diff --git a/src/observer/storage/common/table.h b/src/observer/storage/common/table.h
index a185535be223653dae5735bc50202fae1d12968f..707553724fd7a14b9dc157a87ad92e989be0649a 100644
--- a/src/observer/storage/common/table.h
+++ b/src/observer/storage/common/table.h
@@ -29,6 +29,7 @@ class IndexScanner;
 class RecordDeleter;
 class Trx;
 
+// TODO remove the routines with condition
 class Table {
 public:
   Table() = default;
diff --git a/src/observer/storage/default/disk_buffer_pool.cpp b/src/observer/storage/default/disk_buffer_pool.cpp
index e3953aee84d496ccaa929345db651ebf53eb3862..18a24508acb486e2aa9b9d2c5d0dea977bb63a20 100644
--- a/src/observer/storage/default/disk_buffer_pool.cpp
+++ b/src/observer/storage/default/disk_buffer_pool.cpp
@@ -295,6 +295,8 @@ RC DiskBufferPool::allocate_page(Frame **frame)
 
 RC DiskBufferPool::unpin_page(Frame *frame)
 {
+  assert(frame->pin_count_ >= 1);
+
   if (--frame->pin_count_ == 0) {
     PageNum page_num = frame->page_num();
     auto pages_it = disposed_pages.find(page_num);
diff --git a/src/observer/storage/index/bplus_tree.cpp b/src/observer/storage/index/bplus_tree.cpp
index 50e49f19ecca7e1b78c357025a2558a41bc3758d..0e7a62d68cf3eb69273195fdee001b972ea30935 100644
--- a/src/observer/storage/index/bplus_tree.cpp
+++ b/src/observer/storage/index/bplus_tree.cpp
@@ -1443,10 +1443,10 @@ RC BplusTreeHandler::insert_entry(const char *user_key, const RID *rid)
   return RC::SUCCESS;
 }
 
-RC BplusTreeHandler::get_entry(const char *user_key, std::list<RID> &rids)
+RC BplusTreeHandler::get_entry(const char *user_key, int key_len, std::list<RID> &rids)
 {
   BplusTreeScanner scanner(*this);
-  RC rc = scanner.open(user_key, true/*left_inclusive*/, user_key, true/*right_inclusive*/);
+  RC rc = scanner.open(user_key, key_len, true/*left_inclusive*/, user_key, key_len, true/*right_inclusive*/);
   if (rc != RC::SUCCESS) {
     LOG_WARN("failed to open scanner. rc=%d:%s", rc, strrc(rc));
     return rc;
@@ -1721,8 +1721,8 @@ BplusTreeScanner::~BplusTreeScanner()
   close();
 }
 
-RC BplusTreeScanner::open(const char *left_user_key, bool left_inclusive,
-                          const char *right_user_key, bool right_inclusive)
+RC BplusTreeScanner::open(const char *left_user_key, int left_len, bool left_inclusive,
+                          const char *right_user_key, int right_len, bool right_inclusive)
 {
   RC rc = RC::SUCCESS;
   if (inited_) {
@@ -1753,10 +1753,30 @@ RC BplusTreeScanner::open(const char *left_user_key, bool left_inclusive,
     iter_index_ = 0;
   } else {
     char *left_key = nullptr;
-    if (left_inclusive) { 
-      left_key = tree_handler_.make_key(left_user_key, *RID::min());
+
+    char *fixed_left_key = const_cast<char *>(left_user_key);
+    if (tree_handler_.file_header_.attr_type == CHARS) {
+      bool should_inclusive_after_fix = false;
+      rc = fix_user_key(left_user_key, left_len, true/*greater*/, &fixed_left_key, &should_inclusive_after_fix);
+      if (rc != RC::SUCCESS) {
+	LOG_WARN("failed to fix left user key. rc=%s", strrc(rc));
+	return rc;
+      }
+
+      if (should_inclusive_after_fix) {
+	left_inclusive = true;
+      }
+    }
+
+    if (left_inclusive) {
+      left_key = tree_handler_.make_key(fixed_left_key, *RID::min());
     } else {
-      left_key = tree_handler_.make_key(left_user_key, *RID::max());
+      left_key = tree_handler_.make_key(fixed_left_key, *RID::max());
+    }
+
+    if (fixed_left_key != left_user_key) {
+      delete[] fixed_left_key;
+      fixed_left_key = nullptr;
     }
     rc = tree_handler_.find_leaf(left_key, left_frame_);
 
@@ -1800,10 +1820,28 @@ RC BplusTreeScanner::open(const char *left_user_key, bool left_inclusive,
   } else {
 
     char *right_key = nullptr;
+    char *fixed_right_key = const_cast<char *>(right_user_key);
+    bool should_include_after_fix = false;
+    if (tree_handler_.file_header_.attr_type == CHARS) {
+      rc = fix_user_key(right_user_key, right_len, false/*want_greater*/, &fixed_right_key, &should_include_after_fix);
+      if (rc != RC::SUCCESS) {
+	LOG_WARN("failed to fix right user key. rc=%s", strrc(rc));
+	return rc;
+      }
+
+      if (should_include_after_fix) {
+	right_inclusive = true;
+      }
+    }
     if (right_inclusive) {
-      right_key = tree_handler_.make_key(right_user_key, *RID::max());
+      right_key = tree_handler_.make_key(fixed_right_key, *RID::max());
     } else {
-      right_key = tree_handler_.make_key(right_user_key, *RID::min());
+      right_key = tree_handler_.make_key(fixed_right_key, *RID::min());
+    }
+
+    if (fixed_right_key != right_user_key) {
+      delete[] fixed_right_key;
+      fixed_right_key = nullptr;
     }
 
     rc = tree_handler_.find_leaf(right_key, right_frame_);
@@ -1883,11 +1921,13 @@ RC BplusTreeScanner::next_entry(RID *rid)
     PageNum page_num = node.next_page();
     tree_handler_.disk_buffer_pool_->unpin_page(left_frame_);
     if (page_num == BP_INVALID_PAGE_NUM) {
+      left_frame_ = nullptr;
       LOG_WARN("got invalid next page. page num=%d", page_num);
       rc = RC::INTERNAL;
     } else {
       rc = tree_handler_.disk_buffer_pool_->get_this_page(page_num, &left_frame_);
       if (rc != RC::SUCCESS) {
+	left_frame_ = nullptr;
         LOG_WARN("failed to fetch next page. page num=%d, rc=%d:%s", page_num, rc, strrc(rc));
         return rc;
       }
@@ -1906,12 +1946,64 @@ RC BplusTreeScanner::close()
 {
   if (left_frame_ != nullptr) {
     tree_handler_.disk_buffer_pool_->unpin_page(left_frame_);
+    left_frame_ = nullptr;
   }
   if (right_frame_ != nullptr) {
     tree_handler_.disk_buffer_pool_->unpin_page(right_frame_);
+    right_frame_ = nullptr;
   }
   end_index_ = -1;
   inited_ = false;
   LOG_INFO("bplus tree scanner closed");
   return RC::SUCCESS;
 }
+
+RC BplusTreeScanner::fix_user_key(const char *user_key, int key_len, bool want_greater,
+			      char **fixed_key, bool *should_inclusive)
+{
+  if (nullptr == fixed_key || nullptr == should_inclusive) {
+    return RC::INVALID_ARGUMENT;
+  }
+
+  // 这里很粗暴，变长字段才需要做调整，其它默认都不需要做调整
+  assert(tree_handler_.file_header_.attr_type == CHARS);
+  assert(strlen(user_key) >= static_cast<size_t>(key_len));
+  
+  *should_inclusive = false;
+  
+  int32_t attr_length = tree_handler_.file_header_.attr_length;
+  char *key_buf = new (std::nothrow)char [attr_length];
+  if (nullptr == key_buf) {
+    return RC::NOMEM;
+  }
+
+  if (key_len <= attr_length) {
+    memcpy(key_buf, user_key, key_len);
+    memset(key_buf + key_len, 0, attr_length - key_len);
+
+    *fixed_key = key_buf;
+    return RC::SUCCESS;
+  }
+
+  // key_len > attr_length
+  memcpy(key_buf, user_key, attr_length);
+
+  char c = user_key[attr_length];
+  if (c == 0) {
+    *fixed_key = key_buf;
+    return RC::SUCCESS;
+  }
+
+  // 扫描 >=/> user_key 的数据
+  // 示例：>=/> ABCD1 的数据，attr_length=4,
+  //      等价于扫描 >= ABCE 的数据
+  // 如果是扫描 <=/< user_key的数据
+  // 示例：<=/< ABCD1  <==> <= ABCD  (attr_length=4)
+  *should_inclusive = true;
+  if (want_greater) {
+    key_buf[attr_length - 1]++;
+  }
+  
+  *fixed_key = key_buf;
+  return RC::SUCCESS;
+}
diff --git a/src/observer/storage/index/bplus_tree.h b/src/observer/storage/index/bplus_tree.h
index 91d9d483fbf13598f147dc36349e79ce3144e90d..7a09b1b25e5ef49a72864371aa5c9f62649958a4 100644
--- a/src/observer/storage/index/bplus_tree.h
+++ b/src/observer/storage/index/bplus_tree.h
@@ -118,7 +118,14 @@ public:
       return std::to_string(*(float*)v);
     }
     case CHARS: {
-      return std::string(v, attr_length_);
+      std::string str;
+      for (int i = 0; i < attr_length_; i++) {
+	if (v[i] == 0) {
+	  break;
+	}
+	str.push_back(v[i]);
+      }
+      return str;
     }
     default:{
       LOG_ERROR("unknown attr type. %d", attr_type_);
@@ -400,12 +407,14 @@ public:
    * 此函数向IndexHandle对应的索引中插入一个索引项。
    * 参数user_key指向要插入的属性值，参数rid标识该索引项对应的元组，
    * 即向索引中插入一个值为（user_key，rid）的键值对
+   * @note 这里假设user_key的内存大小与attr_length 一致
    */
   RC insert_entry(const char *user_key, const RID *rid);
 
   /**
    * 从IndexHandle句柄对应的索引中删除一个值为（*pData，rid）的索引项
    * @return RECORD_INVALID_KEY 指定值不存在
+   * @note 这里假设user_key的内存大小与attr_length 一致
    */
   RC delete_entry(const char *user_key, const RID *rid);
 
@@ -413,9 +422,10 @@ public:
 
   /**
    * 获取指定值的record
+   * @param key_len user_key的长度
    * @param rid  返回值，记录记录所在的页面号和slot
    */
-  RC get_entry(const char *user_key, std::list<RID> &rids);
+  RC get_entry(const char *user_key, int key_len, std::list<RID> &rids);
 
   RC sync();
 
@@ -493,18 +503,26 @@ public:
 
   /**
    * 扫描指定范围的数据
-   * @param left_key 扫描范围的左边界，如果是null，则没有左边界
+   * @param left_user_key 扫描范围的左边界，如果是null，则没有左边界
+   * @param left_len left_user_key 的内存大小(只有在变长字段中才会关注)
    * @param left_inclusive 左边界的值是否包含在内
-   * @param right_key 扫描范围的右边界。如果是null，则没有右边界
+   * @param right_user_key 扫描范围的右边界。如果是null，则没有右边界
+   * @param right_len right_user_key 的内存大小(只有在变长字段中才会关注)
    * @param right_inclusive 右边界的值是否包含在内
    */
-  RC open(const char *left_user_key, bool left_inclusive,
-	  const char *right_user_key, bool right_inclusive);
+  RC open(const char *left_user_key, int left_len, bool left_inclusive,
+	  const char *right_user_key, int right_len, bool right_inclusive);
 
   RC next_entry(RID *rid);
 
   RC close();
 
+private:
+  /**
+   * 如果key的类型是CHARS, 扩展或缩减user_key的大小刚好是schema中定义的大小
+   */
+  RC fix_user_key(const char *user_key, int key_len, bool want_greater,
+		  char **fixed_key, bool *should_inclusive);
 private:
   bool inited_ = false;
   BplusTreeHandler &tree_handler_;
diff --git a/src/observer/storage/index/bplus_tree_index.cpp b/src/observer/storage/index/bplus_tree_index.cpp
index ea69bcc0746872317ef583b05d3d1b707a5ccbb7..cbaef5cdefc04aaa253c69763f3bd0e03bf62e81 100644
--- a/src/observer/storage/index/bplus_tree_index.cpp
+++ b/src/observer/storage/index/bplus_tree_index.cpp
@@ -98,11 +98,11 @@ RC BplusTreeIndex::delete_entry(const char *record, const RID *rid)
   return index_handler_.delete_entry(record + field_meta_.offset(), rid);
 }
 
-IndexScanner *BplusTreeIndex::create_scanner(const char *left_key, bool left_inclusive,
-					     const char *right_key, bool right_inclusive)
+IndexScanner *BplusTreeIndex::create_scanner(const char *left_key, int left_len, bool left_inclusive,
+					     const char *right_key, int right_len, bool right_inclusive)
 {
   BplusTreeIndexScanner *index_scanner = new BplusTreeIndexScanner(index_handler_);
-  RC rc = index_scanner->open(left_key, left_inclusive, right_key, right_inclusive);
+  RC rc = index_scanner->open(left_key, left_len, left_inclusive, right_key, right_len, right_inclusive);
   if (rc != RC::SUCCESS) {
     LOG_WARN("failed to open index scanner. rc=%d:%s", rc, strrc(rc));
     delete index_scanner;
@@ -125,9 +125,10 @@ BplusTreeIndexScanner::~BplusTreeIndexScanner() noexcept
   tree_scanner_.close();
 }
 
-RC BplusTreeIndexScanner::open(const char *left_key, bool left_inclusive, const char *right_key, bool right_inclusive)
+RC BplusTreeIndexScanner::open(const char *left_key, int left_len, bool left_inclusive,
+                               const char *right_key, int right_len, bool right_inclusive)
 {
-  return tree_scanner_.open(left_key, left_inclusive, right_key, right_inclusive);
+  return tree_scanner_.open(left_key, left_len, left_inclusive, right_key, right_len, right_inclusive);
 }
 
 RC BplusTreeIndexScanner::next_entry(RID *rid)
diff --git a/src/observer/storage/index/bplus_tree_index.h b/src/observer/storage/index/bplus_tree_index.h
index 1c3ff920f9269c320660621a24ccd934984033dc..c2e66f18227d9f4378287bb2b649a2dd805b7623 100644
--- a/src/observer/storage/index/bplus_tree_index.h
+++ b/src/observer/storage/index/bplus_tree_index.h
@@ -33,8 +33,8 @@ public:
   /**
    * 扫描指定范围的数据
    */
-  IndexScanner *create_scanner(const char *left_key, bool left_inclusive,
-			       const char *right_key, bool right_inclusive) override;
+  IndexScanner *create_scanner(const char *left_key, int left_len, bool left_inclusive,
+			       const char *right_key, int right_len, bool right_inclusive) override;
 
   RC sync() override;
 
@@ -51,7 +51,8 @@ public:
   RC next_entry(RID *rid) override;
   RC destroy() override;
 
-  RC open(const char *left_key, bool left_inclusive, const char *right_key, bool right_inclusive);
+  RC open(const char *left_key, int left_len, bool left_inclusive,
+          const char *right_key, int right_len, bool right_inclusive);
 private:
   BplusTreeScanner tree_scanner_;
 };
diff --git a/src/observer/storage/index/index.h b/src/observer/storage/index/index.h
index d66a09327de2559047fa510db59e143d1a7cca4b..4f04fb4d3c2bf5d96409c670f11ff48ee98c66d8 100644
--- a/src/observer/storage/index/index.h
+++ b/src/observer/storage/index/index.h
@@ -46,8 +46,8 @@ public:
   virtual RC insert_entry(const char *record, const RID *rid) = 0;
   virtual RC delete_entry(const char *record, const RID *rid) = 0;
 
-  virtual IndexScanner *create_scanner(const char *left_key, bool left_inclusive,
-				       const char *right_key, bool right_inclusive) = 0;
+  virtual IndexScanner *create_scanner(const char *left_key, int left_len, bool left_inclusive,
+				       const char *right_key, int right_len, bool right_inclusive) = 0;
 
   virtual RC sync() = 0;
 
diff --git a/src/observer/util/comparator.cpp b/src/observer/util/comparator.cpp
index f7e6a8ee44735f196a59b13897203ff03dcd2b7b..1c8615fdc34e8e87876b6459ae5d3922ba66cacf 100644
--- a/src/observer/util/comparator.cpp
+++ b/src/observer/util/comparator.cpp
@@ -13,6 +13,7 @@ See the Mulan PSL v2 for more details. */
 //
 
 #include <string.h>
+#include <algorithm>
 
 const double epsilon = 1E-6;
 
@@ -37,9 +38,22 @@ int compare_float(void *arg1, void *arg2)
   return 0;
 }
 
-int compare_string(void *arg1, void *arg2, int maxlen)
+int compare_string(void *arg1, int arg1_max_length, void *arg2, int arg2_max_length)
 {
   const char *s1 = (const char *)arg1;
   const char *s2 = (const char *)arg2;
-  return strncmp(s1, s2, maxlen);
+  int maxlen = std::min(arg1_max_length, arg2_max_length);
+  int result =  strncmp(s1, s2, maxlen);
+  if (0 != result) {
+    return result;
+  }
+
+  if (arg1_max_length > maxlen) {
+    return s1[maxlen] - 0;
+  }
+
+  if (arg2_max_length > maxlen) {
+    return 0 - s2[maxlen];
+  }
+  return 0;
 }
diff --git a/src/observer/util/comparator.h b/src/observer/util/comparator.h
index c80e9f2237c6fb9a90602a0176f09587d819db86..18ab99fddd08874d6e59d9b615501b4be78fcd13 100644
--- a/src/observer/util/comparator.h
+++ b/src/observer/util/comparator.h
@@ -16,4 +16,4 @@ See the Mulan PSL v2 for more details. */
 
 int compare_int(void *arg1, void *arg2);
 int compare_float(void *arg1, void *arg2);
-int compare_string(void *arg1, void *arg2, int max_length);
+int compare_string(void *arg1, int arg1_max_length, void *arg2, int arg2_max_length);
diff --git a/unitest/bplus_tree_test.cpp b/unitest/bplus_tree_test.cpp
index 5fa48fd2c90c4cf43a54f98eec9b11cfa3392795..dabfe08ee6d5815955b97560c94ce56dad5177b6 100644
--- a/unitest/bplus_tree_test.cpp
+++ b/unitest/bplus_tree_test.cpp
@@ -31,6 +31,7 @@ using namespace common;
 #define INSERT_NUM (TIMES * ORDER * ORDER * ORDER * ORDER)
 #define POOL_NUM 2
 
+BufferPoolManager bpm;
 BplusTreeHandler *handler = nullptr;
 const char *index_name = "test.btree";
 int insert_num = INSERT_NUM;
@@ -38,6 +39,12 @@ const int page_size = 1024;
 RID rid, check_rid;
 int k = 0;
 
+void init_bpm()
+{
+  if (&BufferPoolManager::instance() == nullptr) {
+    BufferPoolManager::set_instance(&bpm);
+  }
+}
 void test_insert()
 {
   RC rc = RC::SUCCESS;
@@ -148,7 +155,7 @@ void test_get()
     }
 
     rids.clear();
-    RC rc = handler->get_entry((const char *)&i, rids);
+    RC rc = handler->get_entry((const char *)&i, 4, rids);
 
     ASSERT_EQ(RC::SUCCESS, rc);
     ASSERT_EQ(1, rids.size());
@@ -221,7 +228,7 @@ void test_delete()
       LOG_INFO("Begin to get entry of index, i=%d, rid: %s", i, rid.to_string().c_str());
     }
     rids.clear();
-    rc = handler->get_entry((const char *)&i, rids);
+    rc = handler->get_entry((const char *)&i, 4, rids);
     ASSERT_EQ(RC::SUCCESS, rc);
     int t = i % TIMES;
     if (t == 0 || t == 1) {
@@ -458,6 +465,50 @@ TEST(test_bplus_tree, test_internal_index_node_handle)
     ASSERT_EQ(i, index);
   }
 }
+
+TEST(test_bplus_tree, test_chars)
+{
+  LoggerFactory::init_default("test_chars.log");
+
+  const char *index_name = "chars.btree";
+  ::remove(index_name);
+  handler = new BplusTreeHandler();
+  handler->create(index_name, CHARS, 8, ORDER, ORDER);
+
+  char keys[][9] = {
+    "abcdefg",
+    "12345678",
+    "12345678",
+    "abcdefg",
+    "abcdefga"
+  };
+
+  RID rid;
+  RC rc = RC::SUCCESS;
+  for (size_t i = 0; i < sizeof(keys)/sizeof(keys[0]); i++) {
+    rid.page_num = 0;
+    rid.slot_num = i;
+    rc = handler->insert_entry(keys[i], &rid);
+    ASSERT_EQ(RC::SUCCESS, rc);
+  }
+
+  LOG_INFO("begin to print bplus tree of chars");
+  handler->print_tree();
+  LOG_INFO("end to print bplus tree of chars");
+
+  BplusTreeScanner scanner(*handler);
+  const char *key = "abcdefg";
+  rc = scanner.open(key, strlen(key), true, key, strlen(key), true);
+  ASSERT_EQ(rc, RC::SUCCESS);
+
+  int count = 0;
+  while (RC::SUCCESS == (rc = scanner.next_entry(&rid))) {
+    count++;
+  }
+  scanner.close();
+  ASSERT_EQ(2, count);
+}
+
 TEST(test_bplus_tree, test_scanner)
 {
   LoggerFactory::init_default("test.log");
@@ -484,7 +535,7 @@ TEST(test_bplus_tree, test_scanner)
 
   int begin = -100;
   int end = -20;
-  rc = scanner.open((const char *)&begin, false, (const char *)&end, false);
+  rc = scanner.open((const char *)&begin, 4, false, (const char *)&end, 4, false);
   ASSERT_EQ(RC::SUCCESS, rc);
 
   rc = scanner.next_entry(&rid);
@@ -494,7 +545,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = -100;
   end = 1;
-  rc = scanner.open((const char *)&begin, false, (const char *)&end, false);
+  rc = scanner.open((const char *)&begin, 4, false, (const char *)&end, 4, false);
   ASSERT_EQ(RC::SUCCESS, rc);
   rc = scanner.next_entry(&rid);
   ASSERT_EQ(RC::RECORD_EOF, rc);
@@ -503,7 +554,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = -100;
   end = 1;
-  rc = scanner.open((const char *)&begin, false, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, false, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   rc = scanner.next_entry(&rid);
   ASSERT_EQ(RC::SUCCESS, rc);
@@ -514,7 +565,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 1;
   end = 3;
-  rc = scanner.open((const char *)&begin, false, (const char *)&end, false/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, false, (const char *)&end, 4, false/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   rc = scanner.next_entry(&rid);
   ASSERT_EQ(RC::RECORD_EOF, rc);
@@ -523,7 +574,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 1;
   end = 3;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
     count++;
@@ -535,7 +586,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 0;
   end = 3;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -548,7 +599,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 11;
   end = 21;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -561,7 +612,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 11;
   end = 91;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -574,7 +625,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 191;
   end = 199;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -587,7 +638,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 191;
   end = 201;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -600,7 +651,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 200;
   end = 301;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   rc = scanner.next_entry(&rid);
   ASSERT_EQ(RC::RECORD_EOF, rc);
@@ -609,14 +660,14 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 300;
   end = 201;
-  rc = scanner.open((const char *)&begin, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::INVALID_ARGUMENT, rc);
 
   scanner.close();
 
   begin = 300;
   end = 201;
-  rc = scanner.open(nullptr, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open(nullptr, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -629,7 +680,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 300;
   end = 10;
-  rc = scanner.open(nullptr, true, (const char *)&end, true/*inclusive*/);
+  rc = scanner.open(nullptr, 4, true, (const char *)&end, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -642,7 +693,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 190;
   end = 10;
-  rc = scanner.open((const char *)&begin, true, nullptr, true/*inclusive*/);
+  rc = scanner.open((const char *)&begin, 4, true, nullptr, 4, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -655,7 +706,7 @@ TEST(test_bplus_tree, test_scanner)
 
   begin = 190;
   end = 10;
-  rc = scanner.open(nullptr, true, nullptr, true/*inclusive*/);
+  rc = scanner.open(nullptr, 0, true, nullptr, 0, true/*inclusive*/);
   ASSERT_EQ(RC::SUCCESS, rc);
   count = 0;
   while ((rc = scanner.next_entry(&rid)) == RC::SUCCESS) {
@@ -695,6 +746,7 @@ int main(int argc, char **argv)
   // 调用RUN_ALL_TESTS()运行所有测试用例
   // main函数返回RUN_ALL_TESTS()的运行结果
 
+  init_bpm();
   int rc = RUN_ALL_TESTS();
 
   return rc;