Backport of the patch for bug #8457 "Precision math: DIV

returns incorrect result with large decimal value" 
 
For the DIV operator, neither operands nor result were checked 
for integer overflows. 
 
This patch changes the DIV behavior for non-integer operands as 
follows: if either of the operands has a non-integer type, 
convert both operands to the DECIMAL type, then calculate the 
division using DECIMAL arithmetics. Convert the resulting 
DECIMAL value into BIGINT [UNSIGNED] if it fits into the 
corresponding range, or throw an 'out of range' error 
otherwise. 

mysql-test/r/func_math.result:
  Added a test case for bug #8457.
  Fixed results for a test case depending on the wrong behavior.
mysql-test/r/type_varchar.result:
  Fixed results for a test case depending on the wrong behavior.
mysql-test/t/func_math.test:
  Added a test case for bug #8457.
sql/item_func.cc:
  If either of the operands has a non-integer type, convert both 
  operands to the DECIMAL type, then calculate the division using 
  DECIMAL arithmetics. Convert the resulting DECIMAL value into 
  BIGINT [UNSIGNED] if it fits into the corresponding range, or 
  throw an 'out of range' error otherwise.

4 files changed, 57 insertions, 2 deletions

diff --git a/mysql-test/r/func_math.result b/mysql-test/r/func_math.result
index d8b8a14afc6..f469564c78b 100644
--- a/mysql-test/r/func_math.result
+++ b/mysql-test/r/func_math.result
@@ -382,6 +382,9 @@ y
 SELECT b DIV 900 y FROM t1 GROUP BY y;
 y
 0
+Warnings:
+Warning	1366	Incorrect decimal value: '' for column '' at row -1
+Warning	1366	Incorrect decimal value: '' for column '' at row -1
 SELECT c DIV 900 y FROM t1 GROUP BY y;
 y
 0
@@ -482,4 +485,12 @@ RAND(i)
 0.155220427694936
 DROP TABLE t1;
 #
+select 123456789012345678901234567890.123456789012345678901234567890 div 1 as x;
+ERROR 22003: Out of range value for column 'x' at row 1
+select "123456789012345678901234567890.123456789012345678901234567890" div 1 as x;
+ERROR 22003: Out of range value for column 'x' at row 1
+SHOW WARNINGS;
+Level	Code	Message
+Warning	1292	Truncated incorrect DECIMAL value: ''
+Error	1264	Out of range value for column 'x' at row 1
 End of 5.1 tests
diff --git a/mysql-test/r/type_varchar.result b/mysql-test/r/type_varchar.result
index 96042a91bae..94628eb16ee 100644
--- a/mysql-test/r/type_varchar.result
+++ b/mysql-test/r/type_varchar.result
@@ -475,8 +475,9 @@ a	(a DIV 2)
 60	30
 t	0
 Warnings:
-Warning	1292	Truncated incorrect INTEGER value: '1a'
-Warning	1292	Truncated incorrect INTEGER value: 't '
+Warning	1292	Truncated incorrect DECIMAL value: '1a'
+Warning	1366	Incorrect decimal value: '' for column '' at row -1
+Warning	1292	Truncated incorrect DECIMAL value: 't '
 SELECT a,CAST(a AS SIGNED) FROM t1 ORDER BY a;
 a	CAST(a AS SIGNED)
 10	10
diff --git a/mysql-test/t/func_math.test b/mysql-test/t/func_math.test
index 91fdce8addb..b999b1e8c1b 100644
--- a/mysql-test/t/func_math.test
+++ b/mysql-test/t/func_math.test
@@ -309,4 +309,15 @@ DROP TABLE t1;
 
 --echo #
 
+#
+# Bug #8457: Precision math:
+#            DIV returns incorrect result with large decimal value
+# Bug #46606:Casting error for large numbers in 5.4 when 'div' is used
+
+--error ER_WARN_DATA_OUT_OF_RANGE
+select 123456789012345678901234567890.123456789012345678901234567890 div 1 as x;
+--error ER_WARN_DATA_OUT_OF_RANGE
+select "123456789012345678901234567890.123456789012345678901234567890" div 1 as x; 
+SHOW WARNINGS;
+
 --echo End of 5.1 tests
diff --git a/sql/item_func.cc b/sql/item_func.cc
index cf499aaf93c..c0a84e3be28 100644
--- a/sql/item_func.cc
+++ b/sql/item_func.cc
@@ -1348,6 +1348,38 @@ void Item_func_div::fix_length_and_dec()
 longlong Item_func_int_div::val_int()
 {
   DBUG_ASSERT(fixed == 1);
+
+  /*
+    Perform division using DECIMAL math if either of the operands has a
+    non-integer type
+  */
+  if (args[0]->result_type() != INT_RESULT ||
+      args[1]->result_type() != INT_RESULT)
+  {
+    my_decimal value0, value1, tmp;
+    my_decimal *val0, *val1;
+    longlong res;
+    int err;
+
+    val0= args[0]->val_decimal(&value0);
+    val1= args[1]->val_decimal(&value1);
+    if ((null_value= (args[0]->null_value || args[1]->null_value)))
+      return 0;
+
+    if ((err= my_decimal_div(E_DEC_FATAL_ERROR & ~E_DEC_DIV_ZERO, &tmp,
+                             val0, val1, 0)) > 3)
+    {
+      if (err == E_DEC_DIV_ZERO)
+        signal_divide_by_null();
+      return 0;
+    }
+
+    if (my_decimal2int(E_DEC_FATAL_ERROR, &tmp, unsigned_flag, &res) &
+        E_DEC_OVERFLOW)
+      my_error(ER_WARN_DATA_OUT_OF_RANGE, MYF(0), name, 1);
+    return res;
+  }
+  
   longlong value=args[0]->val_int();
   longlong val2=args[1]->val_int();
   if ((null_value= (args[0]->null_value || args[1]->null_value)))