mirror of
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Change cost for REF to take into account cost for 1 extra key read_next
The main difference in code path between EQ_REF and REF is that for REF we have to do an extra read_next on the index to check that there is no more matching rows. Before this patch we added a preference of EQ_REF by ensuring that REF would always estimate to find at least 2 rows. This patch adds the cost of the extra key read_next to REF access and removes the code that limited REF to at least 2 rows. For some queries this can have a big effect as the total estimated rows will be halved for each REF table with 1 rows. multi_range cost calculations are also changed to take into account the difference between EQ_REF and REF. The effect of the patch to the test suite: - About 80 test case changed - Almost all changes where for EXPLAIN where estimated rows for REF where changed from 2 to 1. - A few test cases using explain extended had a change of 'filtered'. This is because of the estimated rows are now closer to the calculated selectivity. - A very few test had a change of table order. This is because the change of estimated rows from 2 to 1 or the small cost change for REF (main.subselect_sj_jcl6, main.group_by, main.dervied_cond_pushdown, main.distinct, main.join_nested, main.order_by, main.join_cache) - No key statistics and the estimated rows are now smaller which cased estimated filtering to be lower. (main.subselect_sj_mat) - The number of total rows are halved. (main.derived_cond_pushdown) - Plans with 1 row changed to use RANGE instead of REF. (main.group_min_max) - ALL changed to REF (main.key_diff) - Key changed from ref + index_only to PRIMARY key for InnoDB, as OPTIMIZER_ROW_LOOKUP_COST + OPTIMIZER_ROW_NEXT_FIND_COST is smaller than OPTIMIZER_KEY_LOOKUP_COST + OPTIMIZER_KEY_NEXT_FIND_COST. (main.join_outer_innodb) - Cost changes printouts (main.opt_trace*) - Result order change (innodb_gis.rtree)
This commit is contained in:
Monty
@ -855,7 +855,7 @@ ON t3.a=1 AND t3.b=t2.b AND t2.b=t4.b AND t2.a>0;
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t3 ALL NULL NULL NULL NULL 2 100.00
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1 SIMPLE t4 ALL NULL NULL NULL NULL 2 100.00 Using join buffer (flat, BNL join)
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1 SIMPLE t2 ref idx_b idx_b 5 test.t3.b 2 100.00 Using where
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1 SIMPLE t2 ref idx_b idx_b 5 test.t3.b 1 100.00 Using where
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1 SIMPLE t1 ALL NULL NULL NULL NULL 3 100.00
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Warnings:
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Note 1003 select `test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b` from `test`.`t3` join `test`.`t4` left join (`test`.`t1` join `test`.`t2`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t3`.`b` and `test`.`t2`.`b` = `test`.`t3`.`b` and `test`.`t2`.`a` > 0 and `test`.`t3`.`b` is not null) where 1
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@ -969,10 +969,10 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t6 ALL NULL NULL NULL NULL 3 100.00 Using where
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1 SIMPLE t8 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 8 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 1 100.00 Using where
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1 SIMPLE t3 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 2 100.00 Using where
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Warnings:
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`a` > 0 and `test`.`t4`.`a` > 0 and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2 and `test`.`t5`.`a` > 0)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t4`.`b` = `test`.`t3`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`a` > 0 and `test`.`t4`.`a` > 0 and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2 and `test`.`t5`.`a` > 0)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t3`.`b` = `test`.`t4`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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INSERT INTO t8 VALUES (-3,12,0), (-1,14,0), (-5,15,0), (-1,11,0), (-4,13,0);
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CREATE INDEX idx_b ON t8(b);
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EXPLAIN EXTENDED
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@ -1017,12 +1017,12 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t5 ALL idx_b NULL NULL NULL 7 100.00 Using where
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1 SIMPLE t7 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t6 ALL NULL NULL NULL NULL 3 100.00 Using where
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1 SIMPLE t8 ref idx_b idx_b 5 test.t5.b 2 100.00 Using where
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1 SIMPLE t8 ref idx_b idx_b 5 test.t5.b 1 100.00 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 8 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 1 100.00 Using where
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1 SIMPLE t3 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 2 100.00 Using where
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Warnings:
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`a` > 0 and `test`.`t4`.`a` > 0 and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10 and `test`.`t8`.`a` >= 0 and `test`.`t5`.`b` is not null)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2 and `test`.`t5`.`a` > 0)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t4`.`b` = `test`.`t3`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`a` > 0 and `test`.`t4`.`a` > 0 and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10 and `test`.`t8`.`a` >= 0 and `test`.`t5`.`b` is not null)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2 and `test`.`t5`.`a` > 0)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t3`.`b` = `test`.`t4`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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INSERT INTO t1 VALUES (-1,133,0), (-2,12,0), (-3,11,0), (-5,15,0);
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CREATE INDEX idx_b ON t1(b);
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CREATE INDEX idx_a ON t0(a);
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@ -1063,17 +1063,17 @@ t0.b=t1.b AND
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(t9.a=1);
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id select_type table type possible_keys key key_len ref rows filtered Extra
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1 SIMPLE t0 ref idx_a idx_a 5 const 2 100.00 Using where
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1 SIMPLE t1 ref idx_b idx_b 5 test.t0.b 2 100.00
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1 SIMPLE t1 ref idx_b idx_b 5 test.t0.b 1 100.00
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1 SIMPLE t9 ALL NULL NULL NULL NULL 3 100.00 Using where; Using join buffer (flat, BNL join)
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1 SIMPLE t5 ALL idx_b NULL NULL NULL 7 100.00 Using where
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1 SIMPLE t7 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t6 ALL NULL NULL NULL NULL 3 100.00 Using where
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1 SIMPLE t8 ref idx_b idx_b 5 test.t5.b 2 100.00 Using where
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1 SIMPLE t8 ref idx_b idx_b 5 test.t5.b 1 100.00 Using where
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1 SIMPLE t2 ALL NULL NULL NULL NULL 8 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 1 100.00 Using where
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1 SIMPLE t3 ALL NULL NULL NULL NULL 2 100.00 Using where
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1 SIMPLE t4 ref idx_b idx_b 5 test.t2.b 2 100.00 Using where
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Warnings:
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10 and `test`.`t5`.`b` is not null)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2 and `test`.`t1`.`a` > 0) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t4`.`b` = `test`.`t3`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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Note 1003 select `test`.`t0`.`a` AS `a`,`test`.`t0`.`b` AS `b`,`test`.`t1`.`a` AS `a`,`test`.`t1`.`b` AS `b`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b`,`test`.`t3`.`a` AS `a`,`test`.`t3`.`b` AS `b`,`test`.`t4`.`a` AS `a`,`test`.`t4`.`b` AS `b`,`test`.`t5`.`a` AS `a`,`test`.`t5`.`b` AS `b`,`test`.`t6`.`a` AS `a`,`test`.`t6`.`b` AS `b`,`test`.`t7`.`a` AS `a`,`test`.`t7`.`b` AS `b`,`test`.`t8`.`a` AS `a`,`test`.`t8`.`b` AS `b`,`test`.`t9`.`a` AS `a`,`test`.`t9`.`b` AS `b` from `test`.`t0` join `test`.`t1` left join (`test`.`t2` left join (`test`.`t3` join `test`.`t4`) on(`test`.`t3`.`a` = 1 and `test`.`t4`.`b` = `test`.`t2`.`b` and `test`.`t2`.`b` is not null) join `test`.`t5` left join (`test`.`t6` join `test`.`t7` left join `test`.`t8` on(`test`.`t8`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` < 10 and `test`.`t5`.`b` is not null)) on(`test`.`t7`.`b` = `test`.`t5`.`b` and `test`.`t6`.`b` >= 2)) on((`test`.`t3`.`b` = 2 or `test`.`t3`.`c` is null) and (`test`.`t6`.`b` = 2 or `test`.`t6`.`c` is null) and (`test`.`t5`.`b` = `test`.`t0`.`b` or `test`.`t3`.`c` is null or `test`.`t6`.`c` is null or `test`.`t8`.`c` is null) and `test`.`t1`.`a` <> 2 and `test`.`t1`.`a` > 0) join `test`.`t9` where `test`.`t0`.`a` = 1 and `test`.`t1`.`b` = `test`.`t0`.`b` and `test`.`t9`.`a` = 1 and (`test`.`t2`.`a` >= 4 or `test`.`t2`.`c` is null) and (`test`.`t3`.`a` < 5 or `test`.`t3`.`c` is null) and (`test`.`t3`.`b` = `test`.`t4`.`b` or `test`.`t3`.`c` is null or `test`.`t4`.`c` is null) and (`test`.`t5`.`a` >= 2 or `test`.`t5`.`c` is null) and (`test`.`t6`.`a` >= 4 or `test`.`t6`.`c` is null) and (`test`.`t7`.`a` <= 2 or `test`.`t7`.`c` is null) and (`test`.`t8`.`a` < 1 or `test`.`t8`.`c` is null) and (`test`.`t8`.`b` = `test`.`t9`.`b` or `test`.`t8`.`c` is null)
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||||
SELECT t0.a,t0.b,t1.a,t1.b,t2.a,t2.b,t3.a,t3.b,t4.a,t4.b,
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||||
t5.a,t5.b,t6.a,t6.b,t7.a,t7.b,t8.a,t8.b,t9.a,t9.b
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||||
FROM t0,t1
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||||
@ -1210,12 +1210,12 @@ EXPLAIN SELECT a, b, c FROM t1 LEFT JOIN (t2, t3) ON c < 3 and b = c;
|
||||
id select_type table type possible_keys key key_len ref rows Extra
|
||||
1 SIMPLE t1 index NULL a 5 NULL 21 Using index
|
||||
1 SIMPLE t2 range b b 5 NULL 3 Using where; Using index
|
||||
1 SIMPLE t3 ref c c 5 test.t2.b 2 Using index
|
||||
1 SIMPLE t3 ref c c 5 test.t2.b 1 Using index
|
||||
EXPLAIN SELECT a, b, c FROM t1 LEFT JOIN (t2, t3) ON b < 3 and b = c;
|
||||
id select_type table type possible_keys key key_len ref rows Extra
|
||||
1 SIMPLE t1 index NULL a 5 NULL 21 Using index
|
||||
1 SIMPLE t2 range b b 5 NULL 3 Using where; Using index
|
||||
1 SIMPLE t3 ref c c 5 test.t2.b 2 Using index
|
||||
1 SIMPLE t3 ref c c 5 test.t2.b 1 Using index
|
||||
SELECT a, b, c FROM t1 LEFT JOIN (t2, t3) ON b < 3 and b = c;
|
||||
a b c
|
||||
NULL 0 0
|
||||
|
||||
Reference in New Issue
Block a user