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Update matching_candidates_in_table() to treat all conditions similar

Browse Source 
Fixed also that the 'with_found_constraint parameter' to
matching_candidates_in_table() is as documented: It is now true only
if there is a reference to a previous table in the WHERE condition for
the current examined table (as it was originally documented)

Changes in test results:
- Filtered was 25% smaller for some queries (expected).
- Some join order changed (probably because the tables had very few rows).
- Some more table scans, probably because there would be fewer returned
  rows.
- Some tests exposes a bug that if there is more filtered rows, then the
  cost for table scan will be higher. This will be fixed in a later commit.
This commit is contained in:
Monty
2021-10-07 20:15:34 +03:00
committed by Sergei Petrunia
parent dc2f0d138d
commit b67144893a
41 changed files with 286 additions and 269 deletions
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120
mysql-test/main/greedy_optimizer.result
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@ -142,52 +142,52 @@ Variable_name Value
Last_query_cost 1693.637037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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 t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
set optimizer_prune_level=0;
select @@optimizer_prune_level;
@@optimizer_prune_level
@ -454,52 +454,52 @@ Variable_name Value
Last_query_cost 1693.637037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 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 t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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 (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 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; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
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 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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 t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 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; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 642.737037
set optimizer_search_depth=1;
select @@optimizer_search_depth;
@@optimizer_search_depth
@ -606,52 +606,52 @@ Variable_name Value
Last_query_cost 1693.637037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 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 t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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 (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 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; Using join buffer (flat, BNL join)
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
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 Using where
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
1 SIMPLE t2 ALL NULL NULL NULL NULL 6
1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
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 t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 844.037037
Last_query_cost 642.737037
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 t1 ALL PRIMARY NULL NULL NULL 3 Using where; Using join buffer (flat, BNL join)
1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 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; Using join buffer (flat, BNL join)
1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
show status like 'Last_query_cost';
Variable_name Value
Last_query_cost 642.737037
drop table t1,t2,t3,t4,t5,t6,t7;
CREATE TABLE t1 (a int, b int, d int, i int);
INSERT INTO t1 VALUES (1,1,1,1);