database/mariadb
1
0
Fork 0
mirror of https://github.com/MariaDB/server.git synced 2025-07-30 16:24:05 +03:00
Code Activity

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

Browse Source 
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
Download Patch File Download Diff File Expand all files Collapse all files

26
mysql-test/main/statistics_json.result
View File

@ -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;

19
mysql-test/main/statistics_json.test
View File

@ -276,3 +276,22 @@ select histogram from mysql.column_stats where table_name = 't1';
drop table t1;
--echo #
--echo # MDEV-26750: Estimation for filtered rows is far off with JSON_HB histogram
--echo #
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;
analyze
select c from t1 where c > '1';
drop table t1;

25
sql/opt_histogram_json.cc
View File

@ -569,21 +569,34 @@ double position_in_interval(Field *field, const uchar *key, uint key_len,
if (field->pos_through_val_str())
{
StringBuffer<64> buf1, buf2, buf3;
String empty_buf1, empty_buf2, empty_buf3;
store_key_image_to_rec_no_null(field, left.data(), left.size());
String *min_str= field->val_str(&buf1, &empty_buf1);
String *min_str= field->val_str(&buf1);
/*
Make sure we've saved a copy of the data, not a pointer into the
field->ptr. We will overwrite the contents of field->ptr with the next
store_key_image_to_rec_no_null call
*/
if (&buf1 != min_str)
buf1.copy(*min_str);
else
buf1.copy();
store_key_image_to_rec_no_null(field, right.data(), right.size());
String *max_str= field->val_str(&buf2, &empty_buf2);
String *max_str= field->val_str(&buf2);
/* Same as above */
if (&buf2 != max_str)
buf2.copy(*max_str);
else
buf2.copy();
store_key_image_to_rec_no_null(field, (const char*)key, key_len);
String *midp_str= field->val_str(&buf3, &empty_buf3);
String *midp_str= field->val_str(&buf3);
res= pos_in_interval_for_string(field->charset(),
(const uchar*)midp_str->ptr(), midp_str->length(),
(const uchar*)min_str->ptr(), min_str->length(),
(const uchar*)max_str->ptr(), max_str->length());
(const uchar*)buf1.ptr(), buf1.length(),
(const uchar*)buf2.ptr(), buf2.length());
}
else
{