From 84a572aabf092a799a81e065d79caa88fdf46ef3 Mon Sep 17 00:00:00 2001
From: "holyfoot/hf@mysql.com/hfmain.(none)" <>
Date: Mon, 21 May 2007 22:22:47 +0500
Subject: [PATCH] Bug #27984 Long Decimal Maths produces truncated results.
 decimal_round failed to perform a correct rounding of a decimal number if its
 first nine digits were '9'. It just sets those digits to 0.

---
 mysql-test/r/type_newdecimal.result | 3 +++
 mysql-test/t/type_newdecimal.test   | 5 +++++
 strings/decimal.c                   | 3 ++-
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/mysql-test/r/type_newdecimal.result b/mysql-test/r/type_newdecimal.result
index cbcab126439..92a5e4fc39c 100644
--- a/mysql-test/r/type_newdecimal.result
+++ b/mysql-test/r/type_newdecimal.result
@@ -1465,4 +1465,7 @@ Error	1264	Out of range value adjusted for column 'cast(a as DECIMAL(3,2))' at r
 Error	1264	Out of range value adjusted for column 'cast(a as DECIMAL(3,2))' at row 1
 Error	1264	Out of range value adjusted for column 'cast(a as DECIMAL(3,2))' at row 1
 Error	1264	Out of range value adjusted for column 'cast(a as DECIMAL(3,2))' at row 1
+SELECT 1.000000000000 * 99.999999999998 / 100 a,1.000000000000 * (99.999999999998 / 100) b;
+a	b
+0.9999999999999800000000000000	0.9999999999999800000000000000
 End of 5.0 tests
diff --git a/mysql-test/t/type_newdecimal.test b/mysql-test/t/type_newdecimal.test
index a7906be79d4..3a62db1bfd7 100644
--- a/mysql-test/t/type_newdecimal.test
+++ b/mysql-test/t/type_newdecimal.test
@@ -1149,4 +1149,9 @@ select cast(a as DECIMAL(3,2)), count(*)
   UNION select 12.1234
  ) t group by 1;
 
+#
+# Bug #27984 Long Decimal Maths produces truncated results 
+#
+
+SELECT 1.000000000000 * 99.999999999998 / 100 a,1.000000000000 * (99.999999999998 / 100) b;
 --echo End of 5.0 tests
diff --git a/strings/decimal.c b/strings/decimal.c
index 1ae75167794..f1f02f3a071 100644
--- a/strings/decimal.c
+++ b/strings/decimal.c
@@ -1517,9 +1517,10 @@ decimal_round(decimal_t *from, decimal_t *to, int scale,
     dec1 *p0= buf0+intg0+max(frac1, frac0);
     dec1 *p1= buf1+intg1+max(frac1, frac0);
 
-    to->buf[0]= 0;
     while (buf0 < p0)
       *(--p1) = *(--p0);
+    if (unlikely(intg1 > intg0))
+      to->buf[0]= 0;
 
     intg0= intg1;
     buf0=to->buf;