MDEV-16316 Replace INT_ITEM references in the code behind ORDER, LIMIT, PROCEDURE clause

1. Adding new methods:
- Item::is_order_clause_position()
- Item_splocal::is_valid_limit_clause_variable_with_error()
- Type_handler::is_order_clause_position_type()
- is_limit_clause_valid_type()
and changing all tests related to the ORDER and LIMIT clauses
like "item->type()==INT_ITEM" to these new methods.

2. Adding a helper function prepare_param() in sql_analyse.cc
and replacing three pieces of duplicate code to prepare_param() calls.
Replacing the test "item->type()!=Item::INT_ITEM" to an equivalent
condition using item->basic_const_item() and type_handler()->result_type().

5 files changed, 67 insertions, 41 deletions

diff --git a/sql/item.h b/sql/item.h
index cd6a993b869..d96541a9c0a 100644
--- a/sql/item.h
+++ b/sql/item.h
@@ -1340,6 +1340,14 @@ public:
     a constant expression. Used in the optimizer to propagate basic constants.
   */
   virtual bool basic_const_item() const { return 0; }
+  /*
+    Test if "this" is an ORDER position (rather than an expression).
+    Notes:
+    - can be called before fix_fields().
+    - local SP variables (even of integer types) are always expressions, not
+      positions. (And they can't be used before fix_fields is called for them).
+  */
+  virtual bool is_order_clause_position() const { return false; }
   /* cloning of constant items (0 if it is not const) */
   virtual Item *clone_item(THD *thd) { return 0; }
   virtual Item* build_clone(THD *thd) { return get_copy(thd); }
@@ -2654,6 +2662,20 @@ public:
   */
   Field *create_field_for_create_select(TABLE *table)
   { return tmp_table_field_from_field_type(table); }
+
+  bool is_valid_limit_clause_variable_with_error() const
+  {
+    /*
+      In case if the variable has an anchored data type, e.g.:
+        DECLARE a TYPE OF t1.a;
+      type_handler() is set to &type_handler_null and this
+      function detects such variable as not valid in LIMIT.
+    */
+    if (type_handler()->is_limit_clause_valid_type())
+      return true;
+    my_error(ER_WRONG_SPVAR_TYPE_IN_LIMIT, MYF(0));
+    return false;
+  }
 };
 
 
@@ -3606,6 +3628,13 @@ public:
     return item_type;
   }
 
+  bool is_order_clause_position() const
+  {
+    DBUG_ASSERT(fixed || state == NO_VALUE);
+    return state == SHORT_DATA_VALUE &&
+           type_handler()->is_order_clause_position_type();
+  }
+
   double val_real()
   {
     return can_return_value() ? value.val_real() : 0e0;
@@ -3808,6 +3837,7 @@ public:
   String *val_str(String*);
   int save_in_field(Field *field, bool no_conversions);
   bool basic_const_item() const { return 1; }
+  bool is_order_clause_position() const { return true; }
   Item *clone_item(THD *thd);
   virtual void print(String *str, enum_query_type query_type);
   Item *neg(THD *thd);
diff --git a/sql/sql_analyse.cc b/sql/sql_analyse.cc
index 351ddb452d8..ce1c136fb44 100644
--- a/sql/sql_analyse.cc
+++ b/sql/sql_analyse.cc
@@ -68,6 +68,25 @@ int compare_decimal2(int* len, const char *s, const char *t)
 }
 
 
+static bool
+prepare_param(THD *thd, Item **item, const char *proc_name, uint pos)
+{
+  if (!(*item)->fixed && (*item)->fix_fields(thd, item))
+  {
+    DBUG_PRINT("info", ("fix_fields() for the parameter %u failed", pos));
+    return true;
+  }
+  if ((*item)->type_handler()->result_type() != INT_RESULT ||
+      !(*item)->basic_const_item() ||
+      (*item)->val_real() < 0)
+  {
+    my_error(ER_WRONG_PARAMETERS_TO_PROCEDURE, MYF(0), proc_name);
+    return true;
+  }
+  return false;
+}
+
+
 Procedure *
 proc_analyse_init(THD *thd, ORDER *param, select_result *result,
 		  List<Item> &field_list)
@@ -88,17 +107,8 @@ proc_analyse_init(THD *thd, ORDER *param, select_result *result,
   else if (param->next)
   {
     // first parameter
-    if (!(*param->item)->fixed && (*param->item)->fix_fields(thd, param->item))
-    {
-      DBUG_PRINT("info", ("fix_fields() for the first parameter failed"));
-      goto err;
-    }
-    if ((*param->item)->type() != Item::INT_ITEM ||
-	(*param->item)->val_real() < 0)
-    {
-      my_error(ER_WRONG_PARAMETERS_TO_PROCEDURE, MYF(0), proc_name);
+    if (prepare_param(thd, param->item, proc_name, 0))
       goto err;
-    }
     pc->max_tree_elements = (uint) (*param->item)->val_int();
     param = param->next;
     if (param->next)  // no third parameter possible
@@ -107,25 +117,12 @@ proc_analyse_init(THD *thd, ORDER *param, select_result *result,
       goto err;
     }
     // second parameter
-    if (!(*param->item)->fixed && (*param->item)->fix_fields(thd, param->item))
-    {
-      DBUG_PRINT("info", ("fix_fields() for the second parameter failed"));
+    if (prepare_param(thd, param->item, proc_name, 1))
       goto err;
-    }
-    if ((*param->item)->type() != Item::INT_ITEM ||
-	(*param->item)->val_real() < 0)
-    {
-      my_error(ER_WRONG_PARAMETERS_TO_PROCEDURE, MYF(0), proc_name);
-      goto err;
-    }
     pc->max_treemem = (uint) (*param->item)->val_int();
   }
-  else if ((*param->item)->type() != Item::INT_ITEM ||
-	   (*param->item)->val_real() < 0)
-  {
-    my_error(ER_WRONG_PARAMETERS_TO_PROCEDURE, MYF(0), proc_name);
+  else if (prepare_param(thd, param->item, proc_name, 0))
     goto err;
-  }
   // if only one parameter was given, it will be the value of max_tree_elements
   else
   {
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 6f1d8b815fe..93810d2041c 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -2887,8 +2887,7 @@ void st_select_lex::print_order(String *str,
     else
     {
       /* replace numeric reference with equivalent for ORDER constant */
-      if (order->item[0]->type() == Item::INT_ITEM &&
-          order->item[0]->basic_const_item())
+      if (order->item[0]->is_order_clause_position())
       {
         /* make it expression instead of integer constant */
         str->append(STRING_WITH_LEN("''"));
@@ -6850,11 +6849,9 @@ Item *LEX::create_item_limit(THD *thd,
 #endif
   safe_to_cache_query= 0;
 
-  if (item->type() != Item::INT_ITEM)
-  {
-    my_error(ER_WRONG_SPVAR_TYPE_IN_LIMIT, MYF(0));
+  if (!item->is_valid_limit_clause_variable_with_error())
     return NULL;
-  }
+
   item->limit_clause_param= true;
   return item;
 }
@@ -6877,11 +6874,8 @@ Item *LEX::create_item_limit(THD *thd,
   Item_splocal *item;
   if (!(item= create_item_spvar_row_field(thd, rh, a, b, spv, start, end)))
     return NULL;
-  if (item->type() != Item::INT_ITEM)
-  {
-    my_error(ER_WRONG_SPVAR_TYPE_IN_LIMIT, MYF(0));
+  if (!item->is_valid_limit_clause_variable_with_error())
     return NULL;
-  }
   item->limit_clause_param= true;
   return item;
 }
diff --git a/sql/sql_select.cc b/sql/sql_select.cc
index 0eecb23a9c3..d676722e6e3 100644
--- a/sql/sql_select.cc
+++ b/sql/sql_select.cc
@@ -22771,12 +22771,7 @@ find_order_in_list(THD *thd, Ref_ptr_array ref_pointer_array,
   uint counter;
   enum_resolution_type resolution;
 
-  /*
-    Local SP variables may be int but are expressions, not positions.
-    (And they can't be used before fix_fields is called for them).
-  */
-  if (order_item->type() == Item::INT_ITEM && order_item->basic_const_item() &&
-      !from_window_spec)
+  if (order_item->is_order_clause_position() && !from_window_spec)
   {						/* Order by position */
     uint count;
     if (order->counter_used)
diff --git a/sql/sql_type.h b/sql/sql_type.h
index dbd50dd77b5..74aacc0e0d1 100644
--- a/sql/sql_type.h
+++ b/sql/sql_type.h
@@ -1031,6 +1031,14 @@ public:
   {
     return false;
   }
+  virtual bool is_order_clause_position_type() const
+  {
+    return false;
+  }
+  virtual bool is_limit_clause_valid_type() const
+  {
+    return false;
+  }
   /**
     Check whether a field type can be partially indexed by a key.
     @param  type   field type
@@ -1906,6 +1914,8 @@ class Type_handler_int_result: public Type_handler_numeric
 public:
   Item_result result_type() const { return INT_RESULT; }
   Item_result cmp_type() const { return INT_RESULT; }
+  bool is_order_clause_position_type() const { return true; }
+  bool is_limit_clause_valid_type() const { return true; }
   virtual ~Type_handler_int_result() {}
   const Type_handler *type_handler_for_comparison() const;
   bool subquery_type_allows_materialization(const Item *inner,