From 88a88636271aee2b89000a99c18d551813f0dcc5 Mon Sep 17 00:00:00 2001
From: Alexey Botchkov <holyfoot@mysql.com>
Date: Mon, 17 Nov 2008 19:41:09 +0400
Subject: [PATCH] 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
---
 mysql-test/r/type_newdecimal.result | 15 +++++++++++++++
 mysql-test/t/type_newdecimal.test   | 10 ++++++++++
 sql/item_func.cc                    |  6 ++++--
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/mysql-test/r/type_newdecimal.result b/mysql-test/r/type_newdecimal.result
index 1bb07534a7f..90b6f524692 100644
--- a/mysql-test/r/type_newdecimal.result
+++ b/mysql-test/r/type_newdecimal.result
@@ -1524,4 +1524,19 @@ select (1.20396873 * 0.89550000 * 0.68000000 * 1.08721696 * 0.99500000 *
 (1.20396873 * 0.89550000 * 0.68000000 * 1.08721696 * 0.99500000 *
 1.01500000 * 1.01500000 * 0.99500000)
 0.812988073953673124592306939480
+create table t1 as select 5.05 / 0.014;
+Warnings:
+Note	1265	Data truncated for column '5.05 / 0.014' at row 1
+show warnings;
+Level	Code	Message
+Note	1265	Data truncated for column '5.05 / 0.014' at row 1
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `5.05 / 0.014` decimal(10,6) default NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+select * from t1;
+5.05 / 0.014
+360.714286
+DROP TABLE t1;
 End of 5.0 tests
diff --git a/mysql-test/t/type_newdecimal.test b/mysql-test/t/type_newdecimal.test
index c44abdb144e..a5331582df6 100644
--- a/mysql-test/t/type_newdecimal.test
+++ b/mysql-test/t/type_newdecimal.test
@@ -1225,4 +1225,14 @@ DROP TABLE t1;
 select (1.20396873 * 0.89550000 * 0.68000000 * 1.08721696 * 0.99500000 *
         1.01500000 * 1.01500000 * 0.99500000);
 
+#
+# Bug #31616 div_precision_increment description looks wrong 
+#
+
+create table t1 as select 5.05 / 0.014;
+show warnings;
+show create table t1;
+select * from t1;
+DROP TABLE t1;
+
 --echo End of 5.0 tests
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;