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Change cost for REF to take into account cost for 1 extra key read_next

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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
2022-12-27 14:49:27 +02:00
parent b5df077e85
commit 3fa99f0c0e
81 changed files with 765 additions and 740 deletions
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8
mysql-test/suite/versioning/r/cte.result
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@@ -61,7 +61,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 4 100.00
2 DERIVED e ALL NULL NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION e ALL mgr-fk NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 2 100.00
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 1 100.00
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 with recursive ancestors as (/* select#2 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` where `test`.`e`.`name` = 'bill' and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1` union /* select#3 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` join `ancestors` `a` where `a`.`emp_id` = `test`.`e`.`mgr` and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1`)/* select#1 */ select `ancestors`.`emp_id` AS `emp_id`,`ancestors`.`name` AS `name`,`ancestors`.`mgr` AS `mgr`,`ancestors`.`salary` AS `salary` from `ancestors`
@@ -102,7 +102,7 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY <derived2> ALL NULL NULL NULL NULL 4 100.00
2 DERIVED e ALL NULL NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION e ALL mgr-fk NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 2 100.00
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 1 100.00
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 with recursive ancestors as (/* select#2 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` where `test`.`e`.`name` = 'bill' and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1` union /* select#3 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` join `ancestors` `a` where `a`.`emp_id` = `test`.`e`.`mgr` and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1`)/* select#1 */ select `ancestors`.`emp_id` AS `emp_id`,`ancestors`.`name` AS `name`,`ancestors`.`mgr` AS `mgr`,`ancestors`.`salary` AS `salary` from `ancestors`
@@ -140,10 +140,10 @@ where e.mgr = a.emp_id
select name from emp where emp_id in (select emp_id from ancestors for system_time as of timestamp @ts_1);
id select_type table type possible_keys key key_len ref rows filtered Extra
1 PRIMARY emp ALL PRIMARY NULL NULL NULL 4 100.00 Using where
1 PRIMARY <derived2> ref key0 key0 5 test.emp.emp_id 2 50.00 FirstMatch(emp)
1 PRIMARY <derived2> ref key0 key0 5 test.emp.emp_id 1 100.00 FirstMatch(emp)
2 DERIVED e ALL NULL NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION e ALL mgr-fk NULL NULL NULL 4 100.00 Using where
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 2 100.00
3 RECURSIVE UNION <derived2> ref key0 key0 5 test.e.mgr 1 100.00
NULL UNION RESULT <union2,3> ALL NULL NULL NULL NULL NULL NULL
Warnings:
Note 1003 with recursive ancestors as (/* select#2 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` where `test`.`e`.`name` = 'bill' and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1` union /* select#3 */ select `test`.`e`.`emp_id` AS `emp_id`,`test`.`e`.`name` AS `name`,`test`.`e`.`mgr` AS `mgr`,`test`.`e`.`salary` AS `salary` from `test`.`emp` FOR SYSTEM_TIME AS OF TIMESTAMP @`ts_1` `e` join `ancestors` `a` where `a`.`emp_id` = `test`.`e`.`mgr` and `test`.`e`.`row_end` > @`ts_1` and `test`.`e`.`row_start` <= @`ts_1`)/* select#1 */ select `test`.`emp`.`name` AS `name` from `test`.`emp` semi join (`ancestors`) where `ancestors`.`emp_id` = `test`.`emp`.`emp_id` and `test`.`emp`.`row_end` = TIMESTAMP'2038-01-19 03:14:07.999999'