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MDEV-23811: With large number of indexes optimizer chooses an ineffic… 
…ient plan

This bug could manifest itself for a query with WHERE condition containing
top level OR formula such that each conjunct contained a single-range
condition supported by the same index. One of these range conditions must
be fully covered by another range condition that is used later in the OR
formula. Additionally at least one of these condition should be ANDed with
a sargable range condition supported by a different index.

There were several attempts to fix related problems for OR conditions after
the backport of range optimizer code from MySQL (commit
0e19f3e). Unfortunately the first of these
fixes contained typo remained unnoticed until recently. This typo bug led
to rejection of valid range accesses. This patch fixed this typo bug.
The fix revealed another two bugs: one in a constructor for SEL_ARG,
the other in the function tree_or(). Both are fixed in this patch.
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@igorbabaev
igorbabaev committed Oct 6, 2020
1 parent 1595189 commit 291be49
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74 mysql-test/r/range.result
View file
@@ -1274,7 +1274,7 @@ SELECT * FROM t1 WHERE
5 <= a AND b = 3 OR
3 <= a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a a 5 NULL 4 Using where; Using index
1 SIMPLE t1 range a a 5 NULL 3 Using where; Using index
SELECT * FROM t1 WHERE
3 <= a AND a <= 5 OR
5 <= a AND b = 3 OR
@@ -3054,5 +3054,77 @@ a b
set eq_range_index_dive_limit=default;
drop table t1;
#
# MDEV-23811: Both disjunct of WHERE condition contain range conditions
# for the same index such that the second range condition
# fully covers the first one. Additionally one of the disjuncts
# contains a range condition for the other index.
#
create table t1 (
pk int primary key auto_increment, a int, b int,
index idx1(a), index idx2(b)
);
insert into t1(a,b) values
(5,50), (1,10), (3,30), (7,70), (8,80), (4,40), (2,20), (6,60);
insert into t1(a,b) select a+10, b+100 from t1;
insert into t1(a,b) select a+20, b+200 from t1;
insert into t1(a,b) select a+30, b+300 from t1;
insert into t1(a,b) select a,b from t1;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
explain select * from t1 where ((a between 3 and 4) and b < 100) or (a between 2 and 5);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where
select * from t1 where ((a between 3 and 4) and b < 100) or (a between 2 and 5);
pk a b
7 2 20
71 2 20
3 3 30
67 3 30
6 4 40
70 4 40
1 5 50
65 5 50
explain select * from t1 where (a between 2 and 5) or ((a between 3 and 4) and b < 100);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where
select * from t1 where (a between 2 and 5) or ((a between 3 and 4) and b < 100);
pk a b
7 2 20
71 2 20
3 3 30
67 3 30
6 4 40
70 4 40
1 5 50
65 5 50
explain select * from t1 where (a between 3 and 4) or ((a between 2 and 5) and b < 100);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where
select * from t1 where (a between 3 and 4) or ((a between 2 and 5) and b < 100);
pk a b
7 2 20
71 2 20
3 3 30
67 3 30
6 4 40
70 4 40
1 5 50
65 5 50
explain select * from t1 where ((a between 2 and 5) and b < 100) or (a between 3 and 4);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where
select * from t1 where ((a between 2 and 5) and b < 100) or (a between 3 and 4);
pk a b
7 2 20
71 2 20
3 3 30
67 3 30
6 4 40
70 4 40
1 5 50
65 5 50
drop table t1;
#
# End of 10.2 tests
#
74 mysql-test/r/range_mrr_icp.result
View file
@@ -1276,7 +1276,7 @@ SELECT * FROM t1 WHERE
5 <= a AND b = 3 OR
3 <= a;
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range a a 5 NULL 4 Using where; Using index
1 SIMPLE t1 range a a 5 NULL 3 Using where; Using index
SELECT * FROM t1 WHERE
3 <= a AND a <= 5 OR
5 <= a AND b = 3 OR
@@ -3066,6 +3066,78 @@ a b
set eq_range_index_dive_limit=default;
drop table t1;
#
# MDEV-23811: Both disjunct of WHERE condition contain range conditions
# for the same index such that the second range condition
# fully covers the first one. Additionally one of the disjuncts
# contains a range condition for the other index.
#
create table t1 (
pk int primary key auto_increment, a int, b int,
index idx1(a), index idx2(b)
);
insert into t1(a,b) values
(5,50), (1,10), (3,30), (7,70), (8,80), (4,40), (2,20), (6,60);
insert into t1(a,b) select a+10, b+100 from t1;
insert into t1(a,b) select a+20, b+200 from t1;
insert into t1(a,b) select a+30, b+300 from t1;
insert into t1(a,b) select a,b from t1;
analyze table t1;
Table Op Msg_type Msg_text
test.t1 analyze status OK
explain select * from t1 where ((a between 3 and 4) and b < 100) or (a between 2 and 5);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where; Rowid-ordered scan
select * from t1 where ((a between 3 and 4) and b < 100) or (a between 2 and 5);
pk a b
1 5 50
3 3 30
6 4 40
7 2 20
65 5 50
67 3 30
70 4 40
71 2 20
explain select * from t1 where (a between 2 and 5) or ((a between 3 and 4) and b < 100);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where; Rowid-ordered scan
select * from t1 where (a between 2 and 5) or ((a between 3 and 4) and b < 100);
pk a b
1 5 50
3 3 30
6 4 40
7 2 20
65 5 50
67 3 30
70 4 40
71 2 20
explain select * from t1 where (a between 3 and 4) or ((a between 2 and 5) and b < 100);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where; Rowid-ordered scan
select * from t1 where (a between 3 and 4) or ((a between 2 and 5) and b < 100);
pk a b
1 5 50
3 3 30
6 4 40
7 2 20
65 5 50
67 3 30
70 4 40
71 2 20
explain select * from t1 where ((a between 2 and 5) and b < 100) or (a between 3 and 4);
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE t1 range idx1,idx2 idx1 5 NULL 11 Using index condition; Using where; Rowid-ordered scan
select * from t1 where ((a between 2 and 5) and b < 100) or (a between 3 and 4);
pk a b
1 5 50
3 3 30
6 4 40
7 2 20
65 5 50
67 3 30
70 4 40
71 2 20
drop table t1;
#
# End of 10.2 tests
#
set optimizer_switch=@mrr_icp_extra_tmp;
2 mysql-test/r/range_vs_index_merge_innodb.result
View file
@@ -369,7 +369,7 @@ WHERE ((ID < 200) AND (Name LIKE 'Ha%' OR (Country > 'A' AND Country < 'ARG')))
OR ((ID BETWEEN 100 AND 200) AND
(Name LIKE 'Pa%' OR (Population > 103000 AND Population < 104000)));
id select_type table type possible_keys key key_len ref rows Extra
1 SIMPLE City index_merge PRIMARY,Population,Country,Name Name,Population,PRIMARY 39,4,4 NULL 307 Using sort_union(Name,Population,PRIMARY); Using where
1 SIMPLE City range PRIMARY,Population,Country,Name PRIMARY 4 NULL 200 Using where
SELECT * FROM City USE INDEX ()
WHERE ((ID < 10) AND (Name LIKE 'H%' OR (Country > 'A' AND Country < 'ARG')))
OR ((ID BETWEEN 100 AND 110) AND
42 mysql-test/t/range.test
View file
@@ -2095,6 +2095,48 @@ set eq_range_index_dive_limit=default;

drop table t1;

--echo #
--echo # MDEV-23811: Both disjunct of WHERE condition contain range conditions
--echo # for the same index such that the second range condition
--echo # fully covers the first one. Additionally one of the disjuncts
--echo # contains a range condition for the other index.
--echo #

create table t1 (
pk int primary key auto_increment, a int, b int,
index idx1(a), index idx2(b)
);
insert into t1(a,b) values
(5,50), (1,10), (3,30), (7,70), (8,80), (4,40), (2,20), (6,60);
insert into t1(a,b) select a+10, b+100 from t1;
insert into t1(a,b) select a+20, b+200 from t1;
insert into t1(a,b) select a+30, b+300 from t1;
insert into t1(a,b) select a,b from t1;

analyze table t1;

let $q1=
select * from t1 where ((a between 3 and 4) and b < 100) or (a between 2 and 5);
eval explain $q1;
eval $q1;

let $q2=
select * from t1 where (a between 2 and 5) or ((a between 3 and 4) and b < 100);
eval explain $q2;
eval $q2;

let $q3=
select * from t1 where (a between 3 and 4) or ((a between 2 and 5) and b < 100);
eval explain $q3;
eval $q3;

let $q4=
select * from t1 where ((a between 2 and 5) and b < 100) or (a between 3 and 4);
eval explain $q4;
eval $q4;

drop table t1;

--echo #
--echo # End of 10.2 tests
--echo #
20 sql/opt_range.cc
View file
@@ -1852,6 +1852,9 @@ SEL_ARG::SEL_ARG(SEL_ARG &arg) :Sql_alloc()
next_key_part=arg.next_key_part;
max_part_no= arg.max_part_no;
use_count=1; elements=1;
next= 0;
if (next_key_part)
++next_key_part->use_count;
}


@@ -8869,9 +8872,15 @@ tree_or(RANGE_OPT_PARAM *param,SEL_TREE *tree1,SEL_TREE *tree2)
}
bool no_imerge_from_ranges= FALSE;

SEL_TREE *rt1= tree1;
SEL_TREE *rt2= tree2;
/* Build the range part of the tree for the formula (1) */
if (sel_trees_can_be_ored(param, tree1, tree2, &ored_keys))
{
if (no_merges1)
rt1= new SEL_TREE(tree1, TRUE, param);
if (no_merges2)
rt2= new SEL_TREE(tree2, TRUE, param);
bool must_be_ored= sel_trees_must_be_ored(param, tree1, tree2, ored_keys);
no_imerge_from_ranges= must_be_ored;

@@ -8929,12 +8938,6 @@ tree_or(RANGE_OPT_PARAM *param,SEL_TREE *tree1,SEL_TREE *tree2)
else if (!no_ranges1 && !no_ranges2 && !no_imerge_from_ranges)
{
/* Build the imerge part of the tree for the formula (1) */
SEL_TREE *rt1= tree1;
SEL_TREE *rt2= tree2;
if (no_merges1)
rt1= new SEL_TREE(tree1, TRUE, param);
if (no_merges2)
rt2= new SEL_TREE(tree2, TRUE, param);
if (!rt1 || !rt2 ||
result->merges.push_back(imerge_from_ranges) ||
imerge_from_ranges->or_sel_tree(param, rt1) ||
@@ -9597,10 +9600,11 @@ key_or(RANGE_OPT_PARAM *param, SEL_ARG *key1,SEL_ARG *key2)

if (!tmp->next_key_part)
{
SEL_ARG *key2_next= key2->next;
if (key2->use_count)
{
SEL_ARG *key2_cpy= new SEL_ARG(*key2);
if (key2_cpy)
if (!key2_cpy)
return 0;
key2= key2_cpy;
}
@@ -9621,7 +9625,7 @@ key_or(RANGE_OPT_PARAM *param, SEL_ARG *key1,SEL_ARG *key2)
Move on to next range in key2
*/
key2->increment_use_count(-1); // Free not used tree
key2=key2->next;
key2=key2_next;
continue;
}
else

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