set @old_debug= @@debug_dbug;
set debug_dbug= "+d,test_pseudo_invisible";
create table t1(a int);
set debug_dbug=@old_debug;
desc t1;
Field	Type	Null	Key	Default	Extra
a	int(11)	YES		NULL	
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
insert into t1 values(1);
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
drop table t1;
set debug_dbug= "+d,test_completely_invisible";
create table t1(a int);
set debug_dbug=@old_debug;
desc t1;
Field	Type	Null	Key	Default	Extra
a	int(11)	YES		NULL	
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
insert into t1 values(1);
select * from t1;
a
1
select invisible ,a from t1;
ERROR 42S22: Unknown column 'invisible' in 'field list'
set debug_dbug= "+d,test_completely_invisible";
select invisible ,a from t1;
invisible	a
9	1
set debug_dbug=@old_debug;
drop table t1;
set debug_dbug= "+d,test_pseudo_invisible";
create table t1(a int);
set debug_dbug=@old_debug;
desc t1;
Field	Type	Null	Key	Default	Extra
a	int(11)	YES		NULL	
insert into t1 values(1);
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 change invisible b int;
ERROR 42S22: Unknown column 'invisible' in 't1'
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 modify invisible char;
ERROR 42S22: Unknown column 'invisible' in 't1'
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 drop invisible;
ERROR 42000: Can't DROP COLUMN `invisible`; check that it exists
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 add invisible int;
ERROR 42S21: Duplicate column name 'invisible'
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 add invisible2 int default 2;
select * from t1;
a	invisible2
1	2
select invisible ,a from t1;
invisible	a
9	1
drop table t1;
set debug_dbug= "+d,test_completely_invisible";
create table t1(a int);
desc t1;
Field	Type	Null	Key	Default	Extra
a	int(11)	YES		NULL	
insert into t1 values(1);
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 change invisible b int;
ERROR 42S22: Unknown column 'invisible' in 't1'
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 modify invisible char;
ERROR 42S22: Unknown column 'invisible' in 't1'
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 drop invisible;
ERROR 42000: Can't DROP COLUMN `invisible`; check that it exists
select * from t1;
a
1
select invisible ,a from t1;
invisible	a
9	1
ALTER table t1 add invisible int;
select * from t1;
a	invisible
1	NULL
select invisible1, invisible ,a from t1;
invisible1	invisible	a
9	NULL	1
ALTER table t1 add hid int default 2;
set debug_dbug= "+d,test_completely_invisible";
select * from t1;
a	invisible	hid
1	NULL	2
select invisible ,a from t1;
invisible	a
NULL	1
drop table t1;
set debug_dbug=@old_debug;
Create table t1( a int default(99) invisible, b int);
insert into t1 values(1);
insert into t1 values(2);
insert into t1 values(3);
insert into t1 values(4);
select * from t1 order by b;
b
1
2
3
4
alter table t1 add index(a);
alter table t1 add index(a,b);
show index from t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
t1	1	a	1	a	A	NULL	NULL	NULL	YES	BTREE		
t1	1	a_2	1	a	A	NULL	NULL	NULL	YES	BTREE		
t1	1	a_2	2	b	A	NULL	NULL	NULL	YES	BTREE		
drop table t1;
set debug_dbug= "+d,test_pseudo_invisible";
Create table t1( a int default(99) invisible, b int);
Create table t2( a int default(99) invisible, b int, unique(invisible));
ERROR 42000: Key column 'invisible' doesn't exist in table
set debug_dbug=@old_debug;
insert into t1 values(1);
insert into t1 values(2);
insert into t1 values(3);
insert into t1 values(4);
select * from t1 order by b;
b
1
2
3
4
select invisible, a, b from t1 order by b;
invisible	a	b
9	99	1
9	99	2
9	99	3
9	99	4
alter table t1 add index(invisible);
ERROR 42000: Key column 'invisible' doesn't exist in table
alter table t1 add index(b,invisible);
ERROR 42000: Key column 'invisible' doesn't exist in table
show index from t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
drop table t1;
set debug_dbug= "+d,test_completely_invisible";
Create table t1( a int default(99) invisible, b int);
Create table t2( a int default(99) invisible, b int, unique(invisible));
ERROR 42000: Key column 'invisible' doesn't exist in table
insert into t1 values(1);
insert into t1 values(2);
insert into t1 values(3);
insert into t1 values(4);
select * from t1 order by b;
b
1
2
3
4
select invisible, a, b from t1 order by b;
invisible	a	b
9	99	1
9	99	2
9	99	3
9	99	4
set debug_dbug=@old_debug;
alter table t1 add index(invisible);
ERROR 42000: Key column 'invisible' doesn't exist in table
alter table t1 add index(b,invisible);
ERROR 42000: Key column 'invisible' doesn't exist in table
show index from t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
drop table t1;
set debug_dbug= "+d,test_completely_invisible,test_invisible_index";
Create table t1( a int default(99) , b int,c int, index(b));
set debug_dbug=@old_debug;
Show index from t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
t1	1	b	1	b	A	NULL	NULL	NULL	YES	BTREE		
select * from INFORMATION_SCHEMA.STATISTICS where TABLE_SCHEMA ='test' and table_name='t1';
TABLE_CATALOG	TABLE_SCHEMA	TABLE_NAME	NON_UNIQUE	INDEX_SCHEMA	INDEX_NAME	SEQ_IN_INDEX	COLUMN_NAME	COLLATION	CARDINALITY	SUB_PART	PACKED	NULLABLE	INDEX_TYPE	COMMENT	INDEX_COMMENT
def	test	t1	1	test	b	1	b	A	NULL	NULL	NULL	YES	BTREE		
show create table t1;
Table	Create Table
t1	CREATE TABLE `t1` (
  `a` int(11) DEFAULT 99,
  `b` int(11) DEFAULT NULL,
  `c` int(11) DEFAULT NULL,
  KEY `b` (`b`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
insert into t1 values(1,1,1);
insert into t1 values(2,2,2);
insert into t1 values(3,3,3);
insert into t1 values(4,4,4);
set debug_dbug= "+d,test_completely_invisible,test_invisible_index";
select invisible, a ,b from t1 order by b;
invisible	a	b
9	1	1
9	2	2
9	3	3
9	4	4
explain select * from t1 where invisible =9;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ref	invisible	invisible	5	const	3	
alter table t1 add x int default 3;
select invisible, a ,b from t1;
invisible	a	b
9	1	1
9	2	2
9	3	3
9	4	4
set debug_dbug=@old_debug;
Show index from t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
t1	1	b	1	b	A	NULL	NULL	NULL	YES	BTREE		
create index a1 on t1(invisible);
ERROR 42000: Key column 'invisible' doesn't exist in table
set debug_dbug= "+d,test_completely_invisible,test_invisible_index";
drop index invisible on t1;
ERROR 42000: Can't DROP INDEX `invisible`; check that it exists
explain select * from t1 where invisible =9;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ref	invisible	invisible	5	const	3	
create index invisible on t1(c);
explain select * from t1 where invisible =9;
id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
1	SIMPLE	t1	ref	invisible_2	invisible_2	5	const	3	
show indexes in t1;
Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment	Index_comment
t1	1	b	1	b	A	NULL	NULL	NULL	YES	BTREE		
t1	1	invisible	1	c	A	NULL	NULL	NULL	YES	BTREE		
t1	1	invisible_2	1	invisible	A	NULL	NULL	NULL	YES	BTREE		
drop table t1;
set @old_debug= @@debug_dbug;