Complete implementation of WL#1469 "Greedy algorithm to search for an optimal execution plan",

consisting of pos-review fixes and improvements.


mysql-test/r/distinct.result:
  Adjusted to account for pre-sorting of tables before optimiziation.
mysql-test/r/func_group.result:
  Adjusted to account for pre-sorting of tables before optimiziation.
mysql-test/r/greedy_optimizer.result:
  - Adjusted to account for pre-sorting of tables before optimiziation.
  - Removed unnecessary test.
  - More comments.
mysql-test/r/select.result:
  - Adjusted to account for pre-sorting of tables before optimiziation.
mysql-test/t/greedy_optimizer.test:
  - Adjusted to account for pre-sorting of tables before optimiziation.
  - Removed unnecessary test.
  - More comments.
sql/mysql_priv.h:
  Moved function print_plan() to sql_test.cc
sql/sql_select.cc:
  - Simplified the recursion in best_extension_by_limited_search()
    and aligned it with its pseudo-code.
  - Renamed functions to better reflect their semantics.
  - Post-review changes of function specifications.
  - Moved function print_plan() to sql_test.cc.
sql/sql_test.cc:
  Moved function print_plan() to sql_test.cc

1 files changed, 124 insertions, 200 deletions

diff --git a/mysql-test/r/greedy_optimizer.result b/mysql-test/r/greedy_optimizer.result
index a63fa4609a0..a6b92d38f74 100644
--- a/mysql-test/r/greedy_optimizer.result
+++ b/mysql-test/r/greedy_optimizer.result
@@ -114,6 +114,82 @@ select @@plan_search_depth;
 select @@heuristic;
 @@heuristic
 1
+set plan_search_depth=63;
+select @@plan_search_depth;
+@@plan_search_depth
+63
+explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	821.838037
+explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	821.838037
+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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+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
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	794.838037
+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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+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
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	794.838037
+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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+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
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	794.838037
+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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+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
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
+1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
+show status like 'Last_query_cost';
+Variable_name	Value
+Last_query_cost	794.838037
 set heuristic=0;
 select @@heuristic;
 @@heuristic
@@ -136,13 +212,13 @@ Variable_name	Value
 Last_query_cost	821.838037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	821.838037
@@ -160,12 +236,12 @@ Variable_name	Value
 Last_query_cost	274.419727
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
 show status like 'Last_query_cost';
 Variable_name	Value
@@ -184,12 +260,12 @@ Variable_name	Value
 Last_query_cost	274.419727
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
@@ -237,8 +313,8 @@ Last_query_cost	794.838037
 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	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 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
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
@@ -261,8 +337,8 @@ Last_query_cost	794.838037
 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	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	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
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
@@ -288,13 +364,13 @@ Variable_name	Value
 Last_query_cost	821.838037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	821.838037
@@ -312,12 +388,12 @@ Variable_name	Value
 Last_query_cost	274.419727
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
 show status like 'Last_query_cost';
 Variable_name	Value
@@ -336,91 +412,15 @@ Variable_name	Value
 Last_query_cost	274.419727
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-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
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	274.419727
-set plan_search_depth=63;
-select @@plan_search_depth;
-@@plan_search_depth
-63
-explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	821.838037
-explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	821.838037
-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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	794.838037
-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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
 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
-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
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	274.419727
-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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
 1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	794.838037
-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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-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
-show status like 'Last_query_cost';
-Variable_name	Value
 Last_query_cost	274.419727
 set heuristic=1;
 select @@heuristic;
@@ -444,13 +444,13 @@ Variable_name	Value
 Last_query_cost	821.838037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
+1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
+1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	821.838037
@@ -468,16 +468,16 @@ Variable_name	Value
 Last_query_cost	794.838037
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
 show status like 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	274.419727
+Last_query_cost	794.838037
 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	
@@ -492,16 +492,16 @@ Variable_name	Value
 Last_query_cost	794.838037
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	274.419727
+Last_query_cost	794.838037
 set plan_search_depth=1;
 select @@plan_search_depth;
 @@plan_search_depth
@@ -545,8 +545,8 @@ Last_query_cost	794.838037
 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	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
 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
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
@@ -569,8 +569,8 @@ Last_query_cost	794.838037
 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	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t1.c12	1	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
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
@@ -596,70 +596,6 @@ Variable_name	Value
 Last_query_cost	821.838037
 explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
 id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	821.838037
-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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	794.838037
-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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-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
-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
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	274.419727
-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	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	794.838037
-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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
-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
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	274.419727
-set plan_search_depth=63;
-select @@plan_search_depth;
-@@plan_search_depth
-63
-explain select t1.c11 from t1, t2, t3, t4, t5, t6, t7 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	
@@ -670,18 +606,6 @@ id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
 show status like 'Last_query_cost';
 Variable_name	Value
 Last_query_cost	821.838037
-explain select t1.c11 from t7, t6, t5, t4, t3, t2, t1 where t1.c12 = t2.c21 and t2.c22 = t3.c31 and t3.c32 = t4.c41 and t4.c42 = t5.c51 and t5.c52 = t6.c61 and t6.c62 = t7.c71;
-id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
-1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t6.c62	1	Using index
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t4.c42	1	Using where
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t3	eq_ref	PRIMARY	PRIMARY	4	test.t2.c22	1	Using where
-1	SIMPLE	t1	ALL	NULL	NULL	NULL	NULL	3	Using where
-show status like 'Last_query_cost';
-Variable_name	Value
-Last_query_cost	821.838037
 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	
@@ -696,16 +620,16 @@ Variable_name	Value
 Last_query_cost	794.838037
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	
-1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	
-1	SIMPLE	t1	eq_ref	PRIMARY	PRIMARY	4	test.t2.c21	1	Using where
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
+1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
 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
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using index
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using index
 show status like 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	274.419727
+Last_query_cost	794.838037
 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	
@@ -720,14 +644,14 @@ Variable_name	Value
 Last_query_cost	794.838037
 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	t6	ALL	NULL	NULL	NULL	NULL	18	
-1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
+1	SIMPLE	t1	ALL	PRIMARY	NULL	NULL	NULL	3	
 1	SIMPLE	t2	ALL	NULL	NULL	NULL	NULL	6	Using where
-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
+1	SIMPLE	t4	ALL	NULL	NULL	NULL	NULL	12	Using where
 1	SIMPLE	t5	eq_ref	PRIMARY	PRIMARY	4	test.t1.c14	1	Using where
+1	SIMPLE	t6	ALL	NULL	NULL	NULL	NULL	18	Using where
 1	SIMPLE	t7	eq_ref	PRIMARY	PRIMARY	4	test.t1.c16	1	Using where
 show status like 'Last_query_cost';
 Variable_name	Value
-Last_query_cost	274.419727
+Last_query_cost	794.838037
 drop table t1,t2,t3,t4,t5,t6,t7;