diff --git a/src/observer/mysql/obmp_stmt_send_piece_data.cpp b/src/observer/mysql/obmp_stmt_send_piece_data.cpp
index 82ee04b7cc..0c4a6c858e 100644
--- a/src/observer/mysql/obmp_stmt_send_piece_data.cpp
+++ b/src/observer/mysql/obmp_stmt_send_piece_data.cpp
@@ -368,24 +368,23 @@ int ObPiece::piece_init(ObSQLSessionInfo &session,
   lib::ContextParam param;
   param.set_mem_attr(session.get_effective_tenant_id(),
                       ObModIds::OB_PL_TEMP, ObCtxIds::DEFAULT_CTX_ID);
-  param.set_page_size(OB_MALLOC_BIG_BLOCK_SIZE);
+  param.set_page_size(OB_MALLOC_NORMAL_BLOCK_SIZE);
   if (OB_FAIL((static_cast<ObPieceCache*>(session.get_piece_cache()))
-                    ->mem_context_->CREATE_CONTEXT(entity, param))) {
+                    ->mem_context_->CREATE_CONTEXT(entity_, param))) {
     LOG_WARN("failed to create ref cursor entity", K(ret));
-  } else if (OB_ISNULL(entity)) {
+  } else if (OB_ISNULL(entity_)) {
     ret = OB_ALLOCATE_MEMORY_FAILED;
     LOG_WARN("failed to alloc ref cursor entity", K(ret));
   } else {
     void *buf = NULL;
     ObPieceBufferArray *buf_array = NULL;
-    ObIAllocator *alloc = &entity->get_arena_allocator();
+    ObIAllocator *alloc = &entity_->get_arena_allocator();
     OV (OB_NOT_NULL(buf = alloc->alloc(sizeof(ObPieceBufferArray))),
         OB_ALLOCATE_MEMORY_FAILED, sizeof(ObPieceBufferArray));
     OX (MEMSET(buf, 0, sizeof(ObPieceBufferArray)));
     OV (OB_NOT_NULL(buf_array = new (buf) ObPieceBufferArray(alloc)));
     OZ (buf_array->reserve(OB_MAX_PIECE_COUNT));
     if (OB_SUCC(ret)) {
-        set_allocator(alloc);
         set_buffer_array(buf_array);
     } else {
       ret = OB_ERR_UNEXPECTED;
diff --git a/src/observer/mysql/obmp_stmt_send_piece_data.h b/src/observer/mysql/obmp_stmt_send_piece_data.h
index 22014b3ca2..bd4f052b3c 100644
--- a/src/observer/mysql/obmp_stmt_send_piece_data.h
+++ b/src/observer/mysql/obmp_stmt_send_piece_data.h
@@ -159,17 +159,18 @@ public:
       param_id_(-1),
       pos_(0),
       buffer_array_(NULL),
-      allocator_(NULL),
       is_null_map_(),
-      err_ret_(OB_SUCCESS) {}
+      err_ret_(OB_SUCCESS),
+      entity_(nullptr) {}
   ~ObPiece() { reset(); }
   void reset()
   {
     if (NULL != buffer_array_) {
       reset_buffer_array();
     }
-    if (NULL != allocator_) {
-      allocator_->reset();
+    if (nullptr != entity_) {
+      DESTROY_CONTEXT(entity_);
+      entity_ = nullptr;
     }
     stmt_id_ = 0;
     param_id_ = -1;
@@ -182,7 +183,7 @@ public:
       for (uint64_t i = 0; i < buffer_array_->count(); i++) {
         ObPieceBuffer piece_buffer = buffer_array_->at(i);
         piece_buffer.~ObPieceBuffer();
-        allocator_->free(&piece_buffer);
+        entity_->get_arena_allocator().free(&piece_buffer);
       }
     }
   }
@@ -193,8 +194,7 @@ public:
   void set_position(uint64_t pos) { pos_ = pos; }
   uint64_t get_position() { return pos_; }
   void add_position() { pos_++; }
-  void set_allocator(ObIAllocator *alloc) { allocator_ = alloc; }
-  ObIAllocator *get_allocator() { return allocator_; }
+  ObIAllocator *get_allocator() { return nullptr != entity_ ? &entity_->get_arena_allocator() : NULL; }
   common::ObBitSet<> &get_is_null_map() { return is_null_map_; }
   void get_is_null_map(char *map, int64_t count) {
     for (int64_t i = 0; i<count; i++) {
@@ -213,9 +213,9 @@ private:
   uint16_t param_id_;
   uint64_t pos_;
   ObPieceBufferArray *buffer_array_;
-  ObIAllocator *allocator_;
   common::ObBitSet<> is_null_map_;
   int err_ret_;
+  lib::MemoryContext entity_;
 };  // end of class ObPiece
 
 class ObPieceCache {