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Fixed bug mdev-6843.

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The function  get_column_range_cardinality() returned a wrong result for any column
containing only null values.
This commit is contained in:
Igor Babaev 2014-10-28 22:31:52 -07:00
parent 2d088e265c
commit 100b10d8ef
4 changed files with 91 additions and 1 deletions
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28
mysql-test/r/selectivity.result
View File

@ -1380,5 +1380,33 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ref a a 5 test.t1.a 10 100.00
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`a` = `test`.`t1`.`a`) and (`test`.`t1`.`a` < 10))
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
#
# Bug mdev-6843: col IS NULL in where condition when col is always NULL
#
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int);
insert into t1 select A.a + B.a* 10 + C.a * 100 from t0 A, t0 B, t0 C;
create table t2 (a int, b int);
insert into t2 select NULL, a from t1;
set use_stat_tables='preferably';
set histogram_size=100;
set optimizer_use_condition_selectivity=4;
analyze table t2 persistent for all;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
explain extended
select * from t2 A straight_join t2 B where A.a is null;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE A ALL NULL NULL NULL NULL 1000 100.00 Using where
1 SIMPLE B ALL NULL NULL NULL NULL 1000 100.00 Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`A`.`a` AS `a`,`test`.`A`.`b` AS `b`,`test`.`B`.`a` AS `a`,`test`.`B`.`b` AS `b` from `test`.`t2` `A` straight_join `test`.`t2` `B` where isnull(`test`.`A`.`a`)
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
set use_stat_tables=@save_use_stat_tables;

28
mysql-test/r/selectivity_innodb.result
View File

@ -1390,6 +1390,34 @@ id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE t2 ref a a 5 test.t1.a 10 100.00
Warnings:
Note 1003 select `test`.`t1`.`a` AS `a`,`test`.`t2`.`a` AS `a`,`test`.`t2`.`b` AS `b` from `test`.`t1` straight_join `test`.`t2` where ((`test`.`t2`.`a` = `test`.`t1`.`a`) and (`test`.`t1`.`a` < 10))
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
#
# Bug mdev-6843: col IS NULL in where condition when col is always NULL
#
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int);
insert into t1 select A.a + B.a* 10 + C.a * 100 from t0 A, t0 B, t0 C;
create table t2 (a int, b int);
insert into t2 select NULL, a from t1;
set use_stat_tables='preferably';
set histogram_size=100;
set optimizer_use_condition_selectivity=4;
analyze table t2 persistent for all;
Table Op Msg_type Msg_text
test.t2 analyze status Engine-independent statistics collected
test.t2 analyze status OK
explain extended
select * from t2 A straight_join t2 B where A.a is null;
id select_type table type possible_keys key key_len ref rows filtered Extra
1 SIMPLE A ALL NULL NULL NULL NULL 1000 100.00 Using where
1 SIMPLE B ALL NULL NULL NULL NULL 1000 100.00 Using join buffer (flat, BNL join)
Warnings:
Note 1003 select `test`.`A`.`a` AS `a`,`test`.`A`.`b` AS `b`,`test`.`B`.`a` AS `a`,`test`.`B`.`b` AS `b` from `test`.`t2` `A` straight_join `test`.`t2` `B` where isnull(`test`.`A`.`a`)
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
set use_stat_tables=@save_use_stat_tables;
set optimizer_switch=@save_optimizer_switch_for_selectivity_test;

29
mysql-test/t/selectivity.test
View File

@ -912,6 +912,35 @@ select * from t1 straight_join t2 where t1.a=t2.a and t1.a<10;
explain extended
select * from t1 straight_join t2 where t1.a=t2.a and t2.a<10;
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
--echo #
--echo # Bug mdev-6843: col IS NULL in where condition when col is always NULL
--echo #
create table t0(a int);
insert into t0 values (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
create table t1(a int);
insert into t1 select A.a + B.a* 10 + C.a * 100 from t0 A, t0 B, t0 C;
create table t2 (a int, b int);
insert into t2 select NULL, a from t1;
set use_stat_tables='preferably';
set histogram_size=100;
set optimizer_use_condition_selectivity=4;
analyze table t2 persistent for all;
explain extended
select * from t2 A straight_join t2 B where A.a is null;
set histogram_size=@save_histogram_size;
set optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
drop table t0,t1,t2;
set use_stat_tables=@save_use_stat_tables;

7
sql/sql_statistics.cc
View File

@ -3502,7 +3502,12 @@ double get_column_range_cardinality(Field *field,
!(range_flag & NEAR_MIN);
if (col_non_nulls < 1)
res= 0; /* this is likely wrong, see MDEV-6843 */
{
if (nulls_incl)
res= col_nulls;
else
res= 0;
}
else if (min_endp && max_endp && min_endp->length == max_endp->length &&
!memcmp(min_endp->key, max_endp->key, min_endp->length))
{