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MDEV-29361 Infinite recursive calls when detecting CTE dependencies

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This patch resolves the problem of improper name resolution of table
references to embedded CTEs for some queries. This improper binding could
lead to
  - infinite sequence of calls of recursive functions
  - crashes due to resolution of null pointers
  - wrong result sets returned by queries
  - bogus error messages

If the definition of a CTE contains with clauses then such CTE is called
embedding CTE while CTEs from the with clauses are called embedded CTEs.
If a table reference used in the definition of an embedded CTE cannot be
resolved within the unit that contains this reference it still may be
resolved against a CTE definition from the with clause with one of the
embedding CTEs.
A table reference can be resolved against a CTE definition if it used in
the the scope of this definition and it refers to the name of the CTE.
Table reference t is in the scope of the CTE definition of CTE cte if
- the definition of cte is an element of a with clause declared as
  RECURSIVE and the reference t belongs either to the unit to which
  this with clause is attached or to one of the elements of this clause
- the definition of cte is an element of a with clause without RECURSIVE
  specifier and the reference t belongs either to the unit to which this
  with clause is attached or to one of the elements from this clause that
  are placed before the definition of cte.
If a table reference can be resolved against several CTE definitions then
it is bound to the most embedded.

The code before this patch not always resolved table references used in
embedded CTE according to the above rules.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
This commit is contained in:
Igor Babaev
2022-09-22 21:40:33 -07:00
parent 9de9f105b5
commit 28ae361857
6 changed files with 1342 additions and 36 deletions
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586
mysql-test/main/cte_recursive.result
View File

@ -5017,5 +5017,591 @@ t2 CREATE TABLE `t2` (
set @@sql_mode=default;
drop table t1,t2;
#
# MDEV-29361: Embedded recursive / non-recursive CTE within
# the scope of another embedded CTE with the same name
#
create table t1 (a int);
insert into t1 values (4), (5);
create table t2 (a int);
insert into t2 values (6), (8);
create table t3 (a int);
insert into t3 values (1), (9);
with recursive
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1;
a
4
5
6
7
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2;
a
6
8
10
with
cte as
(
with recursive
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
6
with
cte as
(
with recursive
x(a) as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select s1.a from x as s1, x
where s1.a = x.a and
x.a in (
with recursive
x(a) as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
6
with
cte as
(
with
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
with recursive
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
6
7
with
cte as
(
with
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
with recursive
y as
(
select a from t1 union select a+1 from y as r1 where a < 7
)
select * from y as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
with
y(a) as
(
select a+5 from t1
)
select * from y as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
select (
with
x as
(
select a from x as r1
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
select (
with
x as
(
select a from x as r1
)
select * from x as s1
where s1.a < 5 and
s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
ERROR 42S02: Table 'test.x' doesn't exist
with
cte as
(
select (
with recursive
x(a) as
(
select a+3 from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a < 8 and
s1.a in (
with recursive
x(a) as
(
select a-2 from t2
union
select a+1 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
r
7
7
with
cte as
(
select (
with recursive
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
r
6
6
create table x (a int);
insert into x values (3), (7), (1), (5), (6);
with
cte as
(
select (
with
x as
(
select ( select a from x as r1 ) as a from t1
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x s2
)
) as r
from t3
)
select * from cte;
ERROR 21000: Subquery returns more than 1 row
with
cte as
(
select (
with
x as
(
select ( select a from x ) as a from t1
)
select exists (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x
)
) as r
from t3
)
select * from cte;
r
1
1
with
cte_e as
(
with
cte as
(
select (
with
x as
(
select ( select a from x ) from t1
)
select exists (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x
)
) as r
from t3
)
select * from cte
)
select s1.*, s2.* from cte_e as s1, cte_e as s2;
r r
1 1
1 1
1 1
1 1
with
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1;
a
4
5
2
6
7
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2;
a
6
8
5
9
3
7
with recursive
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1;
a
4
5
6
7
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2;
a
6
8
10
with
cte as
(
with
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with recursive
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
6
with
cte as
(
with
x as
(
select a from t1 union select a+1 from x as r1 where a < 7
)
select * from x as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
4
6
7
with
cte as
(
with recursive
y as
(
select a from t1 union select a+1 from y as r1 where a < 7
)
select * from y as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
5
6
7
with
cte as
(
with
y(a) as
(
select a+5 from t1
)
select * from y as s1
where s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
)
select * from cte;
a
9
with
cte as
(
select (
with
x as
(
select a from x as r1
)
select * from x as s1
where s1.a in (
with
recursive x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
r
6
6
with
cte as
(
select (
with
x as
(
select a from x as r1
)
select * from x as s1
where s1.a < 5 and
s1.a in (
with
x as
(
select a from t2
union
select a+2 from x as r2 where a < 10
)
select a from x as s2
)
) as r
from t3
)
select * from cte;
r
3
3
drop table t1,t2,t3,x;
#
# End of 10.3 tests
#