Many files:

  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.


sql/sql_class.cc:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.
mysql-test/r/ps_1general.result:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.
mysql-test/r/ps_2myisam.result:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.
mysql-test/r/ps_3innodb.result:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.
mysql-test/r/ps_4heap.result:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.
mysql-test/r/ps_5merge.result:
  Fixed bug #9899: erronious NOT_NULL flag for some attributes
  in the EXPLAIN table.

mysql-test/r/ps_1general.result

@@ -468,13 +468,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	14	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	4	Using filesort
@@ -484,13 +484,13 @@ execute stmt1 using @arg00;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	5	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	5	Y	0	31	8
 def					possible_keys	253	4096	7	Y	0	31	8
 def					key	253	64	7	Y	0	31	8
 def					key_len	8	3	1	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	27	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	range	PRIMARY	PRIMARY	4	NULL	3	Using where; Using filesort

mysql-test/r/ps_2myisam.result

@@ -1151,13 +1151,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	

mysql-test/r/ps_3innodb.result

@@ -1151,13 +1151,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	

mysql-test/r/ps_4heap.result

@@ -1152,13 +1152,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	

mysql-test/r/ps_5merge.result

@@ -1194,13 +1194,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	
@@ -4208,13 +4208,13 @@ execute stmt1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
 def					id	8	3	1	N	32929	0	63
 def					select_type	253	19	6	N	1	31	8
-def					table	253	64	2	N	1	31	8
-def					type	253	10	3	N	1	31	8
+def					table	253	64	2	Y	0	31	8
+def					type	253	10	3	Y	0	31	8
 def					possible_keys	253	4096	0	Y	0	31	8
 def					key	253	64	0	Y	0	31	8
 def					key_len	8	3	0	Y	32928	0	63
 def					ref	253	1024	0	Y	0	31	8
-def					rows	8	10	1	N	32929	0	63
+def					rows	8	10	1	Y	32928	0	63
 def					Extra	253	255	0	N	1	31	8
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t9	ALL	NULL	NULL	NULL	NULL	2	

sql/sql_class.cc

@@ -667,8 +667,10 @@ int THD::send_explain_fields(select_result *result)
   CHARSET_INFO *cs= system_charset_info;
   field_list.push_back(new Item_return_int("id",3, MYSQL_TYPE_LONGLONG));
   field_list.push_back(new Item_empty_string("select_type", 19, cs));
-  field_list.push_back(new Item_empty_string("table", NAME_LEN, cs));
-  field_list.push_back(new Item_empty_string("type", 10, cs));
+  field_list.push_back(item= new Item_empty_string("table", NAME_LEN, cs));
+  item->maybe_null= 1;
+  field_list.push_back(item= new Item_empty_string("type", 10, cs));
+  item->maybe_null= 1;
   field_list.push_back(item=new Item_empty_string("possible_keys",
 						  NAME_LEN*MAX_KEY, cs));
   item->maybe_null=1;
@@ -680,7 +682,9 @@ int THD::send_explain_fields(select_result *result)
   field_list.push_back(item=new Item_empty_string("ref",
 						  NAME_LEN*MAX_REF_PARTS, cs));
   item->maybe_null=1;
-  field_list.push_back(new Item_return_int("rows", 10, MYSQL_TYPE_LONGLONG));
+  field_list.push_back(item= new Item_return_int("rows", 10,
+                                                 MYSQL_TYPE_LONGLONG));
+  item->maybe_null= 1;
   field_list.push_back(new Item_empty_string("Extra", 255, cs));
   return (result->send_fields(field_list,1));
 }