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MDEV-26901: Estimation for filtered rows less precise ... #4

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In Histogram_json_hb::point_selectivity(), do return selectivity of 0.0
when the histogram says so.

The logic of "Do not return 0.0 estimate as it causes a multiply-by-zero
meltdown in cost and cardinality calculations" is moved into
records_in_column_ranges() where it is one *once* per column pair (as
opposed to doing once per range, which can cause the error to add-up
to large number when there are many ranges)
This commit is contained in:
Sergei Petrunia
2022-01-11 17:09:55 +03:00
parent db8f15be93
commit dae20dde4e
6 changed files with 42 additions and 6 deletions
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4
mysql-test/main/selectivity.result
View File

@ -1245,8 +1245,8 @@ EXPLAIN EXTENDED
SELECT * FROM language, country, continent
WHERE country_group = lang_group AND lang_group IS NULL;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE country ALL NULL NULL NULL NULL 2 0.00 Using where
1 SIMPLE language ALL NULL NULL NULL NULL 6 0.00 Using where; Using join buffer (flat, BNL join)
1 SIMPLE country ALL NULL NULL NULL NULL 2 50.00 Using where
1 SIMPLE language ALL NULL NULL NULL NULL 6 16.67 Using where; Using join buffer (flat, BNL join)
1 SIMPLE continent ALL NULL NULL NULL NULL 6 100.00 Using join buffer (incremental, BNL join)
Warnings:
Note 1003 select `test`.`language`.`lang_group` AS `lang_group`,`test`.`language`.`lang` AS `lang`,`test`.`country`.`code` AS `code`,`test`.`country`.`country_group` AS `country_group`,`test`.`continent`.`cont_group` AS `cont_group`,`test`.`continent`.`cont` AS `cont` from `test`.`language` join `test`.`country` join `test`.`continent` where `test`.`language`.`lang_group` = `test`.`country`.`country_group` and `test`.`country`.`country_group` is null

4
mysql-test/main/selectivity_innodb.result
View File

@ -1257,8 +1257,8 @@ EXPLAIN EXTENDED
SELECT * FROM language, country, continent
WHERE country_group = lang_group AND lang_group IS NULL;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE country ALL NULL NULL NULL NULL 2 0.00 Using where
1 SIMPLE language ALL NULL NULL NULL NULL 6 0.00 Using where; Using join buffer (flat, BNL join)
1 SIMPLE country ALL NULL NULL NULL NULL 2 50.00 Using where
1 SIMPLE language ALL NULL NULL NULL NULL 6 16.67 Using where; Using join buffer (flat, BNL join)
1 SIMPLE continent ALL NULL NULL NULL NULL 6 100.00 Using join buffer (incremental, BNL join)
Warnings:
Note 1003 select `test`.`language`.`lang_group` AS `lang_group`,`test`.`language`.`lang` AS `lang`,`test`.`country`.`code` AS `code`,`test`.`country`.`country_group` AS `country_group`,`test`.`continent`.`cont_group` AS `cont_group`,`test`.`continent`.`cont` AS `cont` from `test`.`language` join `test`.`country` join `test`.`continent` where `test`.`language`.`lang_group` = `test`.`country`.`country_group` and `test`.`country`.`country_group` is null

20
mysql-test/main/statistics_json.result
View File

@ -8264,3 +8264,23 @@ ANALYZE SELECT * FROM t1 WHERE f > '00:01:00';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 1000 1000.00 50.00 50.00 Using where
drop table t1;
#
# MDEV-26901: Estimation for filtered rows less precise ... #4
#
create table t1 (f int);
insert into t1 values
(7),(5),(0),(5),(112),(9),(9),(7),(5),(9),
(1),(7),(0),(6),(6),(2),(1),(6),(169),(7);
select f from t1 where f in (77, 1, 144, 73, 14, 12);
f
1
1
set histogram_type= JSON_HB;
analyze table t1 persistent for all;
Table Op Msg_type Msg_text
test.t1 analyze status Engine-independent statistics collected
test.t1 analyze status OK
analyze select f from t1 where f in (77, 1, 144, 73, 14, 12);
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t1 ALL NULL NULL NULL NULL 20 20.00 10.00 10.00 Using where
drop table t1;

16
mysql-test/main/statistics_json.test
View File

@ -429,3 +429,19 @@ ANALYZE TABLE t1 PERSISTENT FOR ALL;
ANALYZE SELECT * FROM t1 WHERE f > '00:01:00';
drop table t1;
--echo #
--echo # MDEV-26901: Estimation for filtered rows less precise ... #4
--echo #
create table t1 (f int);
insert into t1 values
(7),(5),(0),(5),(112),(9),(9),(7),(5),(9),
(1),(7),(0),(6),(6),(2),(1),(6),(169),(7);
select f from t1 where f in (77, 1, 144, 73, 14, 12);
set histogram_type= JSON_HB;
analyze table t1 persistent for all;
analyze select f from t1 where f in (77, 1, 144, 73, 14, 12);
drop table t1;

2
sql/opt_histogram_json.cc
View File

@ -921,7 +921,7 @@ double Histogram_json_hb::point_selectivity(Field *field, key_range *endpoint,
The bucket has a single value and it doesn't match! Return a very
small value.
*/
sel= 1.0 / total_rows;
sel= 0.0;
}
else
{

2
sql/opt_range.cc
View File

@ -3279,7 +3279,7 @@ double records_in_column_ranges(PARAM *param, uint idx,
total_rows += rows;
}
if (total_rows == 0)
total_rows= MY_MIN(1, param->table->stat_records());
total_rows= MY_MIN(1, rows2double(param->table->stat_records()));
return total_rows;
}