Bug#45152 crash with round() function on longtext column in a derived table

The crash happens due to wrong max_length value which is set on
Item_func_round::fix_length_and_dec() stage. The value is set to
args[0]->max_length which is too big in case of LONGTEXT(LONGBLOB) fields.
The fix is to set max_length using float_length() function.

1 files changed, 2 insertions, 2 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index 46e0f30d94e..2421f7e0526 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -1958,8 +1958,8 @@ void Item_func_round::fix_length_and_dec()
   unsigned_flag= args[0]->unsigned_flag;
   if (!args[1]->const_item())
   {
-    max_length= args[0]->max_length;
     decimals= args[0]->decimals;
+    max_length= float_length(decimals);
     if (args[0]->result_type() == DECIMAL_RESULT)
     {
       max_length++;
@@ -1979,8 +1979,8 @@ void Item_func_round::fix_length_and_dec()
 
   if (args[0]->decimals == NOT_FIXED_DEC)
   {
-    max_length= args[0]->max_length;
     decimals= min(decimals_to_set, NOT_FIXED_DEC);
+    max_length= float_length(decimals);
     hybrid_type= REAL_RESULT;
     return;
   }