optimize performance

src/observer/mysql/ob_query_driver.cpp

@@ -212,15 +212,12 @@ int ObQueryDriver::response_query_result(ObResultSet &result,
         // break;
       } else {
         LOG_DEBUG("response row succ", K(*row));
-        ObArenaAllocator *allocator = NULL;
-        if (OB_FAIL(result.get_exec_context().get_convert_charset_allocator(allocator))) {
-          LOG_WARN("fail to get lob fake allocator", K(ret));
-        } else if (OB_NOT_NULL(allocator)) {
-          allocator->reset_remain_one_page();
-        }
       }
       if (OB_SUCC(ret)) {
         ++row_num;
+        if (0 == row_num % RESET_CONVERT_CHARSET_ALLOCATOR_EVERY_X_ROWS) {
+          (void) result.get_exec_context().try_reset_convert_charset_allocator();
+        }
       }
     }
   }

src/observer/mysql/ob_query_driver.h

@@ -37,6 +37,8 @@ class ObMySQLResultSet;
 class ObQueryRetryCtrl;
 class ObQueryDriver
 {
+public:
+  static const int64_t RESET_CONVERT_CHARSET_ALLOCATOR_EVERY_X_ROWS = 32;
 public:
   ObQueryDriver(const ObGlobalContext &gctx,
                 const sql::ObSqlCtx &ctx,

src/sql/engine/ob_exec_context.cpp

@@ -638,6 +638,13 @@ int ObExecContext::get_convert_charset_allocator(ObArenaAllocator *&allocator)
   return ret;
 }
 
+void ObExecContext::try_reset_convert_charset_allocator()
+{
+  if (OB_NOT_NULL(convert_allocator_)) {
+    convert_allocator_->reset_remain_one_page();
+  }
+}
+
 int ObExecContext::get_udf_ctx_mgr(ObUdfCtxMgr *&udf_ctx_mgr)
 {
   int ret = OB_SUCCESS;

src/sql/engine/ob_exec_context.h

@@ -159,6 +159,7 @@ public:
   void reset_expr_op();
   inline bool is_expr_op_ctx_inited() { return expr_op_size_ > 0 && NULL != expr_op_ctx_store_; }
   int get_convert_charset_allocator(common::ObArenaAllocator *&allocator);
+  void try_reset_convert_charset_allocator();
 
   void destroy_eval_allocator();