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Commit 074bef4d authored by Igor Babaev's avatar Igor Babaev
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MDEV-30248 Infinite sequence of recursive calls when processing embedded CTE 

This patch fixes the patch for bug MDEV-30248 that unsatisfactorily
resolved the problem of resolution of references to CTE. In some cases
when such a reference has the same table name as the name of one of
CTEs containing this reference the reference could be resolved incorrectly
that led to an invalid select tree where units could be mutually dependent.
This in its turn could lead to an infinite sequence of recursive calls or
to falls into infinite loops.

The patch also removes LEX::resolve_references_to_cte_in_hanging_cte() as
with the new code for resolution of CTE references the call of this
function is not needed anymore.

Approved by Oleksandr Byelkin <sanja@mariadb.com>
parent f18c2b6c
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Showing with 311 additions and 81 deletions
mysql-test/main/cte_recursive.result
View file @ 074bef4d
......@@ -5604,5 +5604,177 @@ r
3
drop table t1,t2,t3,x;
#
# MDEV-30248: Embedded non-recursive CTE referring to base table 'x'
# within a CTE with name 'x' used in a subquery from
# select list of another CTE
#
CREATE TABLE x (a int) ENGINE=MyISAM;
INSERT INTO x VALUES (3),(7),(1);
CREATE TABLE t1 (b int) ENGINE=MYISAM;
INSERT INTO t1 VALUES (1);
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
c
1
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
c
1
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
c
1
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM y)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
c
3
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM x)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
c
3
WITH x AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT x.c from x;
c
1
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 2 AS b)
SELECT r1.b FROM x AS r1, x AS r2 WHERE r1.b=r2.b
) AS c
)
SELECT cte.c from cte;
c
2
DROP TABLE x;
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
ERROR 42S02: Table 'test.x' doesn't exist
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
ERROR 42S02: Table 'test.x' doesn't exist
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
ERROR 42S02: Table 'test.x' doesn't exist
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM y)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
ERROR 42S02: Table 'test.x' doesn't exist
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM x)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
ERROR 42S02: Table 'test.x' doesn't exist
WITH x AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT x.c from x;
ERROR 42S02: Table 'test.x' doesn't exist
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 2 AS b)
SELECT r1.b FROM x AS r1, x AS r2 WHERE r1.b=r2.b
) AS c
)
SELECT cte.c from cte;
ERROR 42S02: Table 'test.x' doesn't exist
DROP TABLE t1;
#
# End of 10.3 tests
#
mysql-test/main/cte_recursive.test
View file @ 074bef4d
......@@ -3871,6 +3871,129 @@ select * from cte;
drop table t1,t2,t3,x;
--echo #
--echo # MDEV-30248: Embedded non-recursive CTE referring to base table 'x'
--echo # within a CTE with name 'x' used in a subquery from
--echo # select list of another CTE
--echo #
CREATE TABLE x (a int) ENGINE=MyISAM;
INSERT INTO x VALUES (3),(7),(1);
CREATE TABLE t1 (b int) ENGINE=MYISAM;
INSERT INTO t1 VALUES (1);
let $q1=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
eval $q1;
let $q2=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
eval $q2;
let $q3=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y AS (SELECT a FROM x AS t) SELECT b FROM t1)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
eval $q3;
let $q4=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH y(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM y)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
eval $q4;
let $q5=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x(b) AS (SELECT a FROM x AS t LIMIT 1) SELECT b FROM x)
SELECT b FROM x AS r
) AS c
)
SELECT cte.c FROM cte;
eval $q5;
let $q6=
WITH x AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 1 AS b)
SELECT b FROM x AS r
) AS c
)
SELECT x.c from x;
eval $q6;
let $q7=
WITH cte AS
(
SELECT
(
WITH x AS
(WITH x AS (SELECT a FROM x AS t) SELECT 2 AS b)
SELECT r1.b FROM x AS r1, x AS r2 WHERE r1.b=r2.b
) AS c
)
SELECT cte.c from cte;
eval $q7;
DROP TABLE x;
--ERROR ER_NO_SUCH_TABLE
eval $q1;
--ERROR ER_NO_SUCH_TABLE
eval $q2;
--ERROR ER_NO_SUCH_TABLE
eval $q3;
--ERROR ER_NO_SUCH_TABLE
eval $q4;
--ERROR ER_NO_SUCH_TABLE
eval $q5;
--ERROR ER_NO_SUCH_TABLE
eval $q6;
--ERROR ER_NO_SUCH_TABLE
eval $q7;
DROP TABLE t1;
--echo #
--echo # End of 10.3 tests
--echo #
sql/sql_cte.cc
View file @ 074bef4d
......@@ -91,49 +91,6 @@ bool LEX::check_dependencies_in_with_clauses()
}
/**
@brief
Resolve references to CTE in specification of hanging CTE
@details
A CTE to which there are no references in the query is called hanging CTE.
Although such CTE is not used for execution its specification must be
subject to context analysis. All errors concerning references to
non-existing tables or fields occurred in the specification must be
reported as well as all other errors caught at the prepare stage.
The specification of a hanging CTE might contain references to other
CTE outside of the specification and within it if the specification
contains a with clause. This function resolves all such references for
all hanging CTEs encountered in the processed query.
@retval
false on success
true on failure
*/
bool
LEX::resolve_references_to_cte_in_hanging_cte()
{
for (With_clause *with_clause= with_clauses_list;
with_clause; with_clause= with_clause->next_with_clause)
{
for (With_element *with_elem= with_clause->with_list.first;
with_elem; with_elem= with_elem->next)
{
if (!with_elem->is_referenced())
{
TABLE_LIST *first_tbl=
with_elem->spec->first_select()->table_list.first;
TABLE_LIST **with_elem_end_pos= with_elem->head->tables_pos.end_pos;
if (first_tbl && resolve_references_to_cte(first_tbl, with_elem_end_pos))
return true;
}
}
}
return false;
}
/**
@brief
Resolve table references to CTE from a sub-chain of table references
......@@ -279,8 +236,6 @@ LEX::check_cte_dependencies_and_resolve_references()
return false;
if (resolve_references_to_cte(query_tables, query_tables_last))
return true;
if (resolve_references_to_cte_in_hanging_cte())
return true;
return false;
}
......@@ -479,47 +434,33 @@ With_element *find_table_def_in_with_clauses(TABLE_LIST *tbl,
st_unit_ctxt_elem *ctxt)
{
With_element *found= 0;
st_select_lex_unit *top_unit= 0;
for (st_unit_ctxt_elem *unit_ctxt_elem= ctxt;
unit_ctxt_elem;
unit_ctxt_elem= unit_ctxt_elem->prev)
{
st_select_lex_unit *unit= unit_ctxt_elem->unit;
With_clause *with_clause= unit->with_clause;
/*
First look for the table definition in the with clause attached to 'unit'
if there is any such clause.
*/
if (with_clause)
{
found= with_clause->find_table_def(tbl, NULL);
/*
If the reference to tbl that has to be resolved belongs to
the FROM clause of a descendant of top_unit->with_element
and this with element belongs to with_clause then this
element must be used as the barrier for the search in the
the list of CTEs from with_clause unless the clause contains
RECURSIVE.
*/
With_element *barrier= 0;
if (top_unit && !with_clause->with_recursive &&
top_unit->with_element &&
top_unit->with_element->get_owner() == with_clause)
barrier= top_unit->with_element;
found= with_clause->find_table_def(tbl, barrier);
if (found)
break;
}
/*
If 'unit' is the unit that defines a with element then reset 'unit'
to the unit whose attached with clause contains this with element.
*/
With_element *with_elem= unit->with_element;
if (with_elem)
{
if (!(unit_ctxt_elem= unit_ctxt_elem->prev))
break;
unit= unit_ctxt_elem->unit;
}
with_clause= unit->with_clause;
/*
Now look for the table definition in this with clause. If the with clause
contains RECURSIVE the search is performed through all CTE definitions in
clause, otherwise up to the definition of 'with_elem' unless it is NULL.
*/
if (with_clause)
{
found= with_clause->find_table_def(tbl,
with_clause->with_recursive ?
NULL : with_elem);
if (found)
break;
}
top_unit= unit;
}
return found;
}
......
sql/sql_cte.h
View file @ 074bef4d
......@@ -322,8 +322,6 @@ class With_element : public Sql_alloc
friend
bool LEX::resolve_references_to_cte(TABLE_LIST *tables,
TABLE_LIST **tables_last);
friend
bool LEX::resolve_references_to_cte_in_hanging_cte();
};
const uint max_number_of_elements_in_with_clause= sizeof(table_map)*8;
......@@ -435,9 +433,6 @@ class With_clause : public Sql_alloc
friend
bool LEX::check_dependencies_in_with_clauses();
friend
bool LEX::resolve_references_to_cte_in_hanging_cte();
};
inline
......
sql/sql_lex.h
View file @ 074bef4d
......@@ -4051,7 +4051,6 @@ struct LEX: public Query_tables_list
}
bool check_dependencies_in_with_clauses();
bool resolve_references_to_cte_in_hanging_cte();
bool check_cte_dependencies_and_resolve_references();
bool resolve_references_to_cte(TABLE_LIST *tables,
TABLE_LIST **tables_last);
......
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