mirror of
https://github.com/MariaDB/server.git
synced 2025-07-29 05:21:33 +03:00
Improve pruning in greedy_search by sorting tables during search
MDEV-28073 Slow query performance in MariaDB when using many tables The faster we can find a good query plan, the more options we have for finding and pruning (ignoring) bad plans. This patch adds sorting of plans to best_extension_by_limited_search(). The plans, from best_access_path() are sorted according to the numbers of found rows. This allows us to faster find 'good tables' and we are thus able to eliminate 'bad plans' faster. One side effect of this patch is that if two tables have equal cost, the table that which was used earlier in the query is preferred. This allows users to improve plans by reordering eq_ref tables in the order they would like them to be uses. Result changes caused by the patch: - Traces are different as now we print the cost for using tables before we start considering them in the plan. - Table order are changed for some plans. In most cases this is because the plans are equal and tables are in this case sorted according to their usage in the original query. - A few plans was changed as the optimizer was able to find a better plan (that was pruned by the original code). Other things: - Added a new statistic variable: "optimizer_join_prefixes_check_calls", which counts number of calls to best_extension_by_limited_search(). This can be used to check the prune efficiency in greedy_search(). - Added variable "JOIN_TAB::embedded_dependent" to be able to handle XX IN (SELECT..) in the greedy_optimizer. The idea is that we should prune a table if any of the tables in embedded_dependent is not yet read. - When using many tables in a query, there will be some additional memory usage as we need to pre-allocate table of table_count*table_count*sizeof(POSITION) objects (POSITION is 312 bytes for now) to hold the pre-calculated best_access_path() information. This memory usage is offset by the expected performance improvement when using many tables in a query. - Removed the code from an earlier patch to keep the table order in join->best_ref in the original order. This is not needed anymore as we are now sorting the tables for each best_extension_by_limited_search() call.
This commit is contained in:
Monty
Oleg Smirnov
@ -155,9 +155,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -179,9 +179,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -237,9 +237,9 @@ id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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show status like 'Last_query_cost';
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Variable_name Value
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@ -261,9 +261,9 @@ id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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show status like 'Last_query_cost';
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Variable_name Value
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@ -311,9 +311,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -335,9 +335,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -389,9 +389,9 @@ id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using join buffer (flat, BNL join)
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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show status like 'Last_query_cost';
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Variable_name Value
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@ -413,9 +413,9 @@ id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t1 eq_ref PRIMARY PRIMARY 4 test.t2.c21 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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show status like 'Last_query_cost';
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Variable_name Value
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@ -467,9 +467,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -491,9 +491,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -543,9 +543,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -567,9 +567,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -619,9 +619,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using index
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using index
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using index
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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@ -643,9 +643,9 @@ Last_query_cost 844.037037
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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;
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id select_type table type possible_keys key key_len ref rows Extra
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1 SIMPLE t1 ALL PRIMARY NULL NULL NULL 3 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1
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1 SIMPLE t5 eq_ref PRIMARY PRIMARY 4 test.t1.c14 1 Using where
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1 SIMPLE t7 eq_ref PRIMARY PRIMARY 4 test.t1.c16 1 Using where
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1 SIMPLE t3 eq_ref PRIMARY PRIMARY 4 test.t1.c12 1 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 6 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t4 ALL NULL NULL NULL NULL 12 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t6 ALL NULL NULL NULL NULL 18 Using where; Using join buffer (flat, BNL join)
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