Fix for bug #28464: a string argument to 'limit ?' PS - replication fails

Problem: we may get syntactically incorrect queries in the binary log 
if we use a string value user variable executing a PS which 
contains '... limit ?' clause, e.g.
prepare s from "select 1 limit ?"; 
set @A='qwe'; execute s using @A;
  
Fix: raise an error in such cases.

mysql-test/r/limit.result

@@ -91,3 +91,14 @@ select sum(a) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
 c
 28
 drop table t1;
+prepare s from "select 1 limit ?";
+set @a='qwe';
+execute s using @a;
+ERROR HY000: Incorrect arguments to EXECUTE
+prepare s from "select 1 limit 1, ?";
+execute s using @a;
+ERROR HY000: Incorrect arguments to EXECUTE
+prepare s from "select 1 limit ?, ?";
+execute s using @a, @a;
+ERROR HY000: Incorrect arguments to EXECUTE
+End of 5.0 tests

mysql-test/t/limit.test

@@ -71,3 +71,20 @@ explain select sum(a) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
 select sum(a) c FROM t1 WHERE a > 0 ORDER BY c LIMIT 3;
 drop table t1;
 # End of 4.1 tests
+
+#
+# Bug #28464: a string argument to 'limit ?' PS
+#
+
+prepare s from "select 1 limit ?"; 
+set @a='qwe'; 
+--error 1210
+execute s using @a;
+prepare s from "select 1 limit 1, ?";
+--error 1210
+execute s using @a;
+prepare s from "select 1 limit ?, ?";
+--error 1210
+execute s using @a, @a;
+
+--echo End of 5.0 tests

sql/item.cc

@@ -2312,6 +2312,7 @@ default_set_param_func(Item_param *param,
 
 
 Item_param::Item_param(unsigned pos_in_query_arg) :
+  strict_type(FALSE),
   state(NO_VALUE),
   item_result_type(STRING_RESULT),
   /* Don't pretend to be a literal unless value for this item is set. */
@@ -2506,6 +2507,8 @@ bool Item_param::set_from_user_var(THD *thd, const user_var_entry *entry)
   if (entry && entry->value)
   {
     item_result_type= entry->type;
+    if (strict_type && required_result_type != item_result_type)
+      DBUG_RETURN(1);
     switch (entry->type) {
     case REAL_RESULT:
       set_double(*(double*)entry->value);

sql/item.h

@@ -1358,8 +1358,10 @@ class Item_param :public Item
   char cnvbuf[MAX_FIELD_WIDTH];
   String cnvstr;
   Item *cnvitem;
-public:
+  bool strict_type;
+  enum Item_result required_result_type;
 
+public:
   enum enum_item_param_state
   {
     NO_VALUE, NULL_VALUE, INT_VALUE, REAL_VALUE,
@@ -1487,6 +1489,11 @@ public:
     Otherwise return FALSE.
   */
   bool eq(const Item *item, bool binary_cmp) const;
+  void set_strict_type(enum Item_result result_type_arg)
+  {
+    strict_type= TRUE;
+    required_result_type= result_type_arg;
+  }
 };
 
 

sql/sql_yacc.yy

@@ -6216,6 +6216,9 @@ limit_options:
 	;
 limit_option:
         param_marker
+        {
+          ((Item_param *) $1)->set_strict_type(INT_RESULT);
+        }
         | ULONGLONG_NUM { $$= new Item_uint($1.str, $1.length); }
         | LONG_NUM     { $$= new Item_uint($1.str, $1.length); }
         | NUM           { $$= new Item_uint($1.str, $1.length); }