Fixed bug #52636.

Applied the fix for bug #47217 from the mysql-6.0 codebase.
The patch adds not null predicates generated for the left parts
of the equality predicates used for ref accesses. This is done
for such predicates both in where conditions and on conditions.
For the where conditions the not null predicates were generated
but in 5.0/5.1 they actually never were used due to some lame
merge from 4.1 to 5.0. The fix for bug #47217 made these 
predicates to be used in the condition pushed to the tables.
Yet only this patch generates not null predicates for equality
predicated from on conditions of outer joins.
This patch introduces a performance regression that can be
observed on a test case from null_key.test. The regression
will disappear after the fix for bug #57024 from mariadb-5.1
is pulled into mariadb-5.3.
The patch contains many changes in the outputs of the EXPLAIN 
commands since generated not null predicates are considered as
parts of the conditions pushed to join tables and may add
'Usingwhere' in some rows of EXPLAINs where there used
to be no such comments.

1 files changed, 28 insertions, 28 deletions

diff --git a/mysql-test/r/greedy_optimizer.result b/mysql-test/r/greedy_optimizer.result
index c0012c297d1..b8e5fee8de8 100644
--- a/mysql-test/r/greedy_optimizer.result
+++ b/mysql-test/r/greedy_optimizer.result
@@ -144,7 +144,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -156,7 +156,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -168,7 +168,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -180,7 +180,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -224,7 +224,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
@@ -236,7 +236,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
@@ -248,7 +248,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
@@ -260,7 +260,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
@@ -300,7 +300,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
@@ -312,7 +312,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
@@ -324,7 +324,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
@@ -336,7 +336,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
@@ -376,7 +376,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
@@ -388,7 +388,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
@@ -400,7 +400,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
@@ -412,7 +412,7 @@ Variable_name	Value
 Last_query_cost	289.418727
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
 1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
@@ -456,7 +456,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -468,7 +468,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -480,7 +480,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -492,7 +492,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -532,7 +532,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
@@ -544,7 +544,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
@@ -556,7 +556,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
@@ -568,7 +568,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
@@ -608,7 +608,7 @@ Variable_name	Value
 Last_query_cost	821.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -620,7 +620,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using index
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -632,7 +632,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer
@@ -644,7 +644,7 @@ Variable_name	Value
 Last_query_cost	794.837037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c11 = t2.c21 and t1.c12 = t3.c31 and t1.c13 = t4.c41 and t1.c14 = t5.c51 and t1.c15 = t6.c61 and t1.c16 = t7.c71 and t2.c22 = t3.c32 and t2.c23 = t4.c42 and t2.c24 = t5.c52 and t2.c25 = t6.c62 and t2.c26 = t7.c72 and t3.c33 = t4.c43 and t3.c34 = t5.c53 and t3.c35 = t6.c63 and t3.c36 = t7.c73 and t4.c42 = t5.c54 and t4.c43 = t6.c64 and t4.c44 = t7.c74 and t5.c52 = t6.c65 and t5.c53 = t7.c75 and t6.c62 = t7.c76;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where; Using join buffer
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where; Using join buffer