Bug #23280699: MYSQLD GOT SIGNAL 11 IN IS_NULL ON SELECT

               FROM I_S

Issue:
------
There is a difference in the field type created when the
following DDLs are used:

1) CREATE TABLE t0 AS SELECT NULL;
2) CREATE TABLE t0 AS SELECT GREATEST(NULL,NULL);

The first statement creates field of type Field_string and
the second one creates a field of type Field_null.

This creates a problem when the query mentioned in this bug
is used. Since the null_ptr is calculated differently for
Field_null.

Solution:
---------
When there is a function returning null in the select list
as mentioned above, the field should be of type
Field_string.

This was fixed in 5.6+ as part of Bug#14021323. This is a
backport to mysql-5.5.

An incorrect comment in innodb_bug54044.test has been
corrected in all versions.

mysql-test/suite/innodb/r/innodb_bug54044.result

@@ -6,7 +6,13 @@ table_54044	CREATE TEMPORARY TABLE `table_54044` (
   `IF(NULL  IS NOT NULL, NULL, NULL)` binary(0) DEFAULT NULL
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1
 DROP TABLE table_54044;
-CREATE TABLE tmp ENGINE = INNODB AS SELECT COALESCE(NULL, NULL, NULL);
-ERROR HY000: Can't create table 'test.tmp' (errno: -1)
-CREATE TABLE tmp ENGINE = INNODB AS SELECT GREATEST(NULL, NULL);
-ERROR HY000: Can't create table 'test.tmp' (errno: -1)
+CREATE TABLE tmp ENGINE = INNODB
+AS SELECT COALESCE(NULL, NULL, NULL), GREATEST(NULL, NULL), NULL;
+SHOW CREATE TABLE tmp;
+Table	Create Table
+tmp	CREATE TABLE `tmp` (
+  `COALESCE(NULL, NULL, NULL)` binary(0) DEFAULT NULL,
+  `GREATEST(NULL, NULL)` binary(0) DEFAULT NULL,
+  `NULL` binary(0) DEFAULT NULL
+) ENGINE=InnoDB DEFAULT CHARSET=latin1
+DROP TABLE tmp;

mysql-test/suite/innodb/t/innodb_bug54044.test

@@ -10,10 +10,9 @@ CREATE TEMPORARY TABLE table_54044 ENGINE = INNODB
 SHOW CREATE TABLE table_54044;
 DROP TABLE table_54044;
 
-# These 'create table' operations should fail because of
-# using NULL datatype
+# This 'create table' should pass since it uses a Field_string of size 0.
 
---error ER_CANT_CREATE_TABLE
-CREATE TABLE tmp ENGINE = INNODB AS SELECT COALESCE(NULL, NULL, NULL);
---error ER_CANT_CREATE_TABLE
-CREATE TABLE tmp ENGINE = INNODB AS SELECT GREATEST(NULL, NULL);
+CREATE TABLE tmp ENGINE = INNODB
+ AS SELECT COALESCE(NULL, NULL, NULL), GREATEST(NULL, NULL), NULL;
+SHOW CREATE TABLE tmp;
+DROP TABLE tmp;

sql/item.cc

@@ -5360,10 +5360,6 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table, bool fixed_length)
     field= new Field_double((uchar*) 0, max_length, null_ptr, 0, Field::NONE,
 			    name, decimals, 0, unsigned_flag);
     break;
-  case MYSQL_TYPE_NULL:
-    field= new Field_null((uchar*) 0, max_length, Field::NONE,
-			  name, &my_charset_bin);
-    break;
   case MYSQL_TYPE_INT24:
     field= new Field_medium((uchar*) 0, max_length, null_ptr, 0, Field::NONE,
 			    name, 0, unsigned_flag);
@@ -5394,6 +5390,7 @@ Field *Item::tmp_table_field_from_field_type(TABLE *table, bool fixed_length)
     DBUG_ASSERT(0);
     /* If something goes awfully wrong, it's better to get a string than die */
   case MYSQL_TYPE_STRING:
+  case MYSQL_TYPE_NULL:
     if (fixed_length && max_length < CONVERT_IF_BIGGER_TO_BLOB)
     {
       field= new Field_string(max_length, maybe_null, name,