From b8d545156589a9a2d4297e3338498bf8362a559b Mon Sep 17 00:00:00 2001
From: "kroki/tomash@moonlight.intranet" <>
Date: Thu, 16 Nov 2006 13:21:38 +0300
Subject: [PATCH] BUG#17047: CHAR() and IN() can return NULL without signaling
 NULL result

The problem was that some functions (namely IN() starting with 4.1, and
CHAR() starting with 5.0) were returning NULL in certain conditions,
while they didn't set their maybe_null flag.  Because of that there could
be some problems with 'IS NULL' check, and statements that depend on the
function value domain, like CREATE TABLE t1 SELECT 1 IN (2, NULL);.

The fix is to set maybe_null correctly.
---
 mysql-test/r/func_in.result |  8 ++++++++
 mysql-test/t/func_in.test   | 22 +++++++++++++++++++++-
 sql/item_cmpfunc.cc         |  1 -
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/mysql-test/r/func_in.result b/mysql-test/r/func_in.result
index 3cf2afc83d1..f74c63f7260 100644
--- a/mysql-test/r/func_in.result
+++ b/mysql-test/r/func_in.result
@@ -202,3 +202,11 @@ select count(*) from t1 where id not in (1,2);
 count(*)
 1
 drop table t1;
+DROP TABLE IF EXISTS t1;
+CREATE TABLE t1 SELECT 1 IN (2, NULL);
+SELECT should return NULL.
+SELECT * FROM t1;
+1 IN (2, NULL)
+NULL
+DROP TABLE t1;
+End of 4.1 tests
diff --git a/mysql-test/t/func_in.test b/mysql-test/t/func_in.test
index 2ffe5a2d5f7..ffed2aac2a0 100644
--- a/mysql-test/t/func_in.test
+++ b/mysql-test/t/func_in.test
@@ -109,4 +109,24 @@ select count(*) from t1 where id not in (1);
 select count(*) from t1 where id not in (1,2);
 drop table t1;
 
-# End of 4.1 tests
+
+#
+# BUG#17047: CHAR() and IN() can return NULL without signaling NULL
+# result
+#
+# The problem was in the IN() function that ignored maybe_null flags
+# of all arguments except the first (the one _before_ the IN
+# keyword, '1' in the test case below).
+#
+--disable_warnings
+DROP TABLE IF EXISTS t1;
+--enable_warnings
+
+CREATE TABLE t1 SELECT 1 IN (2, NULL);
+--echo SELECT should return NULL.
+SELECT * FROM t1;
+
+DROP TABLE t1;
+
+
+--echo End of 4.1 tests
diff --git a/sql/item_cmpfunc.cc b/sql/item_cmpfunc.cc
index 6b6996160a1..859b4e0ecc1 100644
--- a/sql/item_cmpfunc.cc
+++ b/sql/item_cmpfunc.cc
@@ -1998,7 +1998,6 @@ void Item_func_in::fix_length_and_dec()
     if (cmp_type  == STRING_RESULT)
       in_item->cmp_charset= cmp_collation.collation;
   }
-  maybe_null= args[0]->maybe_null;
   max_length= 1;
 }