Bug#31616 div_precision_increment description looks wrong

Item_func_div didn't calculate the precision of the result properly.
  The result of 5/0.0001 is 5000 so we have to add decimals of the divisor
  to the planned precision.

per-file comments:
  mysql-test/r/type_newdecimal.result
Bug#31616 div_precision_increment description looks wrong
    test result fixed

  mysql-test/t/type_newdecimal.test
Bug#31616 div_precision_increment description looks wrong
    test case

  sql/item_func.cc
Bug#31616 div_precision_increment description looks wrong
    precision must be increased with args[1]->decimals parameter

1 files changed, 4 insertions, 2 deletions

diff --git a/sql/item_func.cc b/sql/item_func.cc
index e663e1fcf83..dfe1082fd73 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -1316,8 +1316,10 @@ my_decimal *Item_func_div::decimal_op(my_decimal *decimal_value)
 
 void Item_func_div::result_precision()
 {
-  uint arg_prec= args[0]->decimal_precision() + prec_increment;
-  uint precision=min(arg_prec, DECIMAL_MAX_PRECISION);
+  uint precision=min(args[0]->decimal_precision() + 
+                     args[1]->decimals + prec_increment,
+                     DECIMAL_MAX_PRECISION);
+
   /* Integer operations keep unsigned_flag if one of arguments is unsigned */
   if (result_type() == INT_RESULT)
     unsigned_flag= args[0]->unsigned_flag | args[1]->unsigned_flag;