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MDEV-26750: Estimation for filtered rows is far off with JSON_HB histogram

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Fix a bug in position_in_interval(). Do not overwrite one interval endpoint
with another.
This commit is contained in:
Sergei Petrunia
2021-10-18 16:31:18 +03:00
parent 27539cd2c8
commit f3f78bed85
3 changed files with 61 additions and 9 deletions
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26
mysql-test/main/statistics_json.result
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@ -4243,12 +4243,12 @@ test t1_json a a-0 a-9 0.0000 3.0000 1.0000 10 JSON_HB {
}
explain extended select * from t1_json where a between 'a-3a' and 'zzzzzzzzz';
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1_json ALL NULL NULL NULL NULL 10 50.00 Using where
1 SIMPLE t1_json ALL NULL NULL NULL NULL 10 58.71 Using where
Warnings:
Note 1003 select `test`.`t1_json`.`a` AS `a` from `test`.`t1_json` where `test`.`t1_json`.`a` between 'a-3a' and 'zzzzzzzzz'
analyze select * from t1_json where a between 'a-3a' and 'zzzzzzzzz';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE t1_json ALL NULL NULL NULL NULL 10 10.00 50.00 60.00 Using where
1 SIMPLE t1_json ALL NULL NULL NULL NULL 10 10.00 58.71 60.00 Using where
explain extended select * from t1_json where a < 'b-1a';
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t1_json ALL NULL NULL NULL NULL 10 90.00 Using where
@ -7280,7 +7280,7 @@ Percentage 0.0 99.9 47 JSON_HB {
}
analyze select * from Country use index () where Code between 'BBC' and 'GGG';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE Country ALL NULL NULL NULL NULL 239 239.00 25.10 25.52 Using where
1 SIMPLE Country ALL NULL NULL NULL NULL 239 239.00 24.58 25.52 Using where
analyze select * from Country use index () where Code < 'BBC';
id select_type table type possible_keys key key_len ref rows r_rows filtered r_filtered Extra
1 SIMPLE Country ALL NULL NULL NULL NULL 239 239.00 8.37 7.11 Using where
@ -7510,3 +7510,23 @@ histogram
]
}
drop table t1;
#
# MDEV-26750: Estimation for filtered rows is far off with JSON_HB histogram
#
create table t1 (c char(8));
insert into t1 values ('1x');
insert into t1 values ('1x');
insert into t1 values ('1xx');
insert into t1 values ('0xx');
insert into t1 select * from t1;
insert into t1 select * from t1;
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 c from t1 where c > '1';
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 16 16.00 75.00 75.00 Using where
drop table t1;