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Commit49076fd

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Fix list-manipulation bug in WITH RECURSIVE processing.
makeDependencyGraphWalker and checkWellFormedRecursionWalkerthought they could hold onto a pointer to a list's firstcons cell while the list was modified by recursive calls.That was okay when the cons cell was actually separatelypalloc'd ... but since commit1cff1b9, it's quite unsafe,leading to core dumps or incorrect complaints of faultyWITH nesting.In the field this'd require at least a seven-deep WITH nestto cause an issue, but enabling DEBUG_LIST_MEMORY_USAGEallows the bug to be seen with lesser nesting depths.Per bug #16801 from Alexander Lakhin. Back-patch to v13.Michael Paquier and Tom LaneDiscussion:https://postgr.es/m/16801-393c7922143eaa4d@postgresql.org
1 parent1f56ae3 commit49076fd

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3 files changed

+109
-6
lines changed

3 files changed

+109
-6
lines changed

‎src/backend/parser/parse_cte.c

Lines changed: 6 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -537,15 +537,15 @@ makeDependencyGraphWalker(Node *node, CteState *cstate)
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* In the non-RECURSIVE case, query names are visible to the
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* WITH items after them and to the main query.
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*/
540-
ListCell*cell1;
541-
542540
cstate->innerwiths=lcons(NIL,cstate->innerwiths);
543-
cell1=list_head(cstate->innerwiths);
544541
foreach(lc,stmt->withClause->ctes)
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{
546543
CommonTableExpr*cte= (CommonTableExpr*)lfirst(lc);
544+
ListCell*cell1;
547545

548546
(void)makeDependencyGraphWalker(cte->ctequery,cstate);
547+
/* note that recursion could mutate innerwiths list */
548+
cell1=list_head(cstate->innerwiths);
549549
lfirst(cell1)=lappend((List*)lfirst(cell1),cte);
550550
}
551551
(void)raw_expression_tree_walker(node,
@@ -813,15 +813,15 @@ checkWellFormedRecursionWalker(Node *node, CteState *cstate)
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* In the non-RECURSIVE case, query names are visible to the
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* WITH items after them and to the main query.
815815
*/
816-
ListCell*cell1;
817-
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cstate->innerwiths=lcons(NIL,cstate->innerwiths);
819-
cell1=list_head(cstate->innerwiths);
820817
foreach(lc,stmt->withClause->ctes)
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{
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CommonTableExpr*cte= (CommonTableExpr*)lfirst(lc);
820+
ListCell*cell1;
823821

824822
(void)checkWellFormedRecursionWalker(cte->ctequery,cstate);
823+
/* note that recursion could mutate innerwiths list */
824+
cell1=list_head(cstate->innerwiths);
825825
lfirst(cell1)=lappend((List*)lfirst(cell1),cte);
826826
}
827827
checkWellFormedSelectStmt(stmt,cstate);

‎src/test/regress/expected/with.out

Lines changed: 59 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -167,6 +167,65 @@ ERROR: operator does not exist: text + integer
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LINE 4: SELECT n+1 FROM t WHERE n < 10
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^
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HINT: No operator matches the given name and argument types. You might need to add explicit type casts.
170+
-- Deeply nested WITH caused a list-munging problem in v13
171+
-- Detection of cross-references and self-references
172+
WITH RECURSIVE w1(c1) AS
173+
(WITH w2(c2) AS
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(WITH w3(c3) AS
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(WITH w4(c4) AS
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(WITH w5(c5) AS
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(WITH RECURSIVE w6(c6) AS
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(WITH w6(c6) AS
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(WITH w8(c8) AS
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(SELECT 1)
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SELECT * FROM w8)
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SELECT * FROM w6)
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SELECT * FROM w6)
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SELECT * FROM w5)
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SELECT * FROM w4)
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SELECT * FROM w3)
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SELECT * FROM w2)
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SELECT * FROM w1;
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c1
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----
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1
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(1 row)
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-- Detection of invalid self-references
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WITH RECURSIVE outermost(x) AS (
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SELECT 1
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UNION (WITH innermost1 AS (
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SELECT 2
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UNION (WITH innermost2 AS (
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SELECT 3
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UNION (WITH innermost3 AS (
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SELECT 4
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UNION (WITH innermost4 AS (
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SELECT 5
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UNION (WITH innermost5 AS (
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SELECT 6
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UNION (WITH innermost6 AS
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(SELECT 7)
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SELECT * FROM innermost6))
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SELECT * FROM innermost5))
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SELECT * FROM innermost4))
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SELECT * FROM innermost3))
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SELECT * FROM innermost2))
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SELECT * FROM outermost
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UNION SELECT * FROM innermost1)
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)
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SELECT * FROM outermost ORDER BY 1;
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x
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---
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1
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2
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3
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4
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5
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6
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7
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(7 rows)
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170229
--
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-- Some examples with a tree
172231
--

‎src/test/regress/sql/with.sql

Lines changed: 44 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -87,6 +87,50 @@ UNION ALL
8787
)
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SELECT n, n IS OF (int)AS is_intFROM t;
8989

90+
-- Deeply nested WITH caused a list-munging problem in v13
91+
-- Detection of cross-references and self-references
92+
WITH RECURSIVE w1(c1)AS
93+
(WITH w2(c2)AS
94+
(WITH w3(c3)AS
95+
(WITH w4(c4)AS
96+
(WITH w5(c5)AS
97+
(WITH RECURSIVE w6(c6)AS
98+
(WITH w6(c6)AS
99+
(WITH w8(c8)AS
100+
(SELECT1)
101+
SELECT*FROM w8)
102+
SELECT*FROM w6)
103+
SELECT*FROM w6)
104+
SELECT*FROM w5)
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SELECT*FROM w4)
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SELECT*FROM w3)
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SELECT*FROM w2)
108+
SELECT*FROM w1;
109+
-- Detection of invalid self-references
110+
WITH RECURSIVE outermost(x)AS (
111+
SELECT1
112+
UNION (WITH innermost1AS (
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SELECT2
114+
UNION (WITH innermost2AS (
115+
SELECT3
116+
UNION (WITH innermost3AS (
117+
SELECT4
118+
UNION (WITH innermost4AS (
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SELECT5
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UNION (WITH innermost5AS (
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SELECT6
122+
UNION (WITH innermost6AS
123+
(SELECT7)
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SELECT*FROM innermost6))
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SELECT*FROM innermost5))
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SELECT*FROM innermost4))
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SELECT*FROM innermost3))
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SELECT*FROM innermost2))
129+
SELECT*FROM outermost
130+
UNIONSELECT*FROM innermost1)
131+
)
132+
SELECT*FROM outermostORDER BY1;
133+
90134
--
91135
-- Some examples with a tree
92136
--

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