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greedy_search() and best_extension_by_limited_search() scrambled table order

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best_extension_by_limited_search() assumes that tables should be sorted
according to size to be able to quickly disregard bad plans. However the
current usage of swap_variables() will change the table order to a not
sorted one for the next recursive call. This breaks the assumtion and
causes performance issues when using many tables (we have to examine
many more plans).

This patch fixes this by ensuring that the original table order is kept
for the not yet used tables when best_extension_by_limited_search() is
called.

This was done by always calling swap_variables() for each table and
restoring the original table order at exit.

Some test changed:
- In a majority of the test the change was that two "identical tables"
  where swapped and the optimzer is now using the first/smaller table
- In few test the table order was changed. The new plan looks identical
  or slighly better than the original.
This commit is contained in:
Michael Widenius
2022-05-15 15:46:29 +03:00
committed by Sergei Petrunia
parent f0ea7f7f33
commit 64f24b776d
13 changed files with 196 additions and 179 deletions
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4
mysql-test/main/join_nested.result
View File

@ -916,11 +916,11 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t6 ALL NULL NULL NULL NULL 3 100.00 Using where
1 SIMPLE t8 ALL NULL NULL NULL NULL 2 100.00 Using where
1 SIMPLE t2 ALL NULL NULL NULL NULL 8 100.00 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 2 100.00 Using where
1 SIMPLE t3 ALL NULL NULL NULL NULL 2 100.00 Using where
1 SIMPLE t4 ALL NULL NULL NULL NULL 2 100.00 Using where
1 SIMPLE t9 ALL NULL NULL NULL NULL 3 100.00 Using where; Using join buffer (flat, BNL join)
Warnings:
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) 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)) 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`.`t9`.`b` = `test`.`t8`.`b` or `test`.`t8`.`c` is null)
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) 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)) 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`.`t9`.`b` = `test`.`t8`.`b` or `test`.`t8`.`c` is null)
INSERT INTO t4 VALUES (-3,12,0), (-4,13,0), (-1,11,0), (-3,11,0), (-5,15,0);
INSERT INTO t5 VALUES (-3,11,0), (-2,12,0), (-3,13,0), (-4,12,0);
CREATE INDEX idx_b ON t4(b);