From bc7c439e6b496937f6862f1397e881bf639f71f7 Mon Sep 17 00:00:00 2001
From: Gleb Shchepa <gshchepa@mysql.com>
Date: Tue, 13 Oct 2009 21:50:08 +0500
Subject: [PATCH] Backport of fix to bug #33629 into mysql-next-mr-bugfixing.

Bug #33629: last_day function can return null, but has 'not null' flag set for result

LAST_DAY and MAKEDATE functions are documented as
returning NULL value, but actually they was implemented
as returning NOT NULL typed values.

That caused a confusing error "ERROR 1048 (23000): Column
'...' cannot be null" on queries like:

  SELECT 1 FROM (SELECT LAST_DAY('0')) a;
---
 mysql-test/r/func_sapdb.result |  2 +-
 mysql-test/r/func_time.result  |  2 +-
 mysql-test/r/type_date.result  | 22 ++++++++++++++++++++++
 mysql-test/t/type_date.test    | 18 ++++++++++++++++++
 sql/item_timefunc.h            |  6 ++++++
 5 files changed, 48 insertions(+), 2 deletions(-)

diff --git a/mysql-test/r/func_sapdb.result b/mysql-test/r/func_sapdb.result
index bbc5390895b..87b88692a34 100644
--- a/mysql-test/r/func_sapdb.result
+++ b/mysql-test/r/func_sapdb.result
@@ -194,7 +194,7 @@ date("1997-12-31 23:59:59.000001") as f8,
 time("1997-12-31 23:59:59.000001") as f9;
 describe t1;
 Field	Type	Null	Key	Default	Extra
-f1	date	NO		0000-00-00	
+f1	date	YES		NULL	
 f2	datetime	YES		NULL	
 f3	time	YES		NULL	
 f4	time	YES		NULL	
diff --git a/mysql-test/r/func_time.result b/mysql-test/r/func_time.result
index 0fa143d95bc..5e72b69c41d 100644
--- a/mysql-test/r/func_time.result
+++ b/mysql-test/r/func_time.result
@@ -814,7 +814,7 @@ create table t1 select last_day('2000-02-05') as a,
 from_days(to_days("960101")) as b;
 describe t1;
 Field	Type	Null	Key	Default	Extra
-a	date	NO		0000-00-00	
+a	date	YES		NULL	
 b	date	YES		NULL	
 select * from t1;
 a	b
diff --git a/mysql-test/r/type_date.result b/mysql-test/r/type_date.result
index f96e07b0c5e..92be736ff9a 100644
--- a/mysql-test/r/type_date.result
+++ b/mysql-test/r/type_date.result
@@ -276,3 +276,25 @@ a
 0000-00-01
 drop table t1;
 End of 5.1 tests
+#
+# Bug #33629: last_day function can return null, but has 'not null'
+#             flag set for result
+#
+SELECT 1 FROM (SELECT LAST_DAY('0')) a;
+1
+1
+Warnings:
+Warning	1292	Incorrect datetime value: '0'
+SELECT 1 FROM (SELECT MAKEDATE(2011,0)) a;
+1
+1
+CREATE TABLE t1 AS
+SELECT LAST_DAY('1970-01-01') AS f1,
+MAKEDATE(1970, 1)      AS f2;
+DESCRIBE t1;
+Field	Type	Null	Key	Default	Extra
+f1	date	YES		NULL	
+f2	date	YES		NULL	
+DROP TABLE t1;
+#
+End of 6.0 tests
diff --git a/mysql-test/t/type_date.test b/mysql-test/t/type_date.test
index aec60bc2dee..db273f90425 100644
--- a/mysql-test/t/type_date.test
+++ b/mysql-test/t/type_date.test
@@ -247,3 +247,21 @@ select * from t1 where a between '0000-00-01' and '0000-00-02';
 drop table t1;
 
 --echo End of 5.1 tests
+
+--echo #
+--echo # Bug #33629: last_day function can return null, but has 'not null'
+--echo #             flag set for result
+--echo #
+
+SELECT 1 FROM (SELECT LAST_DAY('0')) a;
+SELECT 1 FROM (SELECT MAKEDATE(2011,0)) a;
+
+CREATE TABLE t1 AS
+  SELECT LAST_DAY('1970-01-01') AS f1,
+         MAKEDATE(1970, 1)      AS f2;
+DESCRIBE t1;
+DROP TABLE t1;
+
+--echo #
+
+--echo End of 6.0 tests
diff --git a/sql/item_timefunc.h b/sql/item_timefunc.h
index 9e3c2e8c89f..5997bb96efe 100644
--- a/sql/item_timefunc.h
+++ b/sql/item_timefunc.h
@@ -871,6 +871,7 @@ public:
   { 
     decimals=0;
     max_length=MAX_DATE_WIDTH*MY_CHARSET_BIN_MB_MAXLEN;
+    maybe_null= 1;
   }
   longlong val_int();
 };
@@ -1025,4 +1026,9 @@ public:
   Item_func_last_day(Item *a) :Item_date(a) {}
   const char *func_name() const { return "last_day"; }
   bool get_date(MYSQL_TIME *res, uint fuzzy_date);
+  void fix_length_and_dec()
+  { 
+    Item_date::fix_length_and_dec();
+    maybe_null= 1;
+  }
 };