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Richard Guo
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Fix Assert failure in XMLTABLE parser
In an XMLTABLE expression, columns can be marked NOT NULL, and the parser internally fabricates an option named "is_not_null" to represent this. However, the parser also allows users to specify arbitrary option names. This creates a conflict: a user can explicitly use "is_not_null" as an option name and assign it a non-Boolean value, which violates internal assumptions and triggers an assertion failure. To fix, this patch checks whether a user-supplied name collides with the internally reserved option name and raises an error if so. Additionally, the internal name is renamed to "__pg__is_not_null" to further reduce the risk of collision with user-defined names. Reported-by: Евгений Горбанев <gorbanyoves@basealt.ru> Author: Richard Guo <guofenglinux@gmail.com> Reviewed-by: Alvaro Herrera <alvherre@kurilemu.de> Discussion: https://postgr.es/m/6bac9886-65bf-4cec-96bd-e304159f28db@basealt.ru Backpatch-through: 15
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‎src/backend/parser/gram.y

Lines changed: 11 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -14230,7 +14230,7 @@ xmltable_column_el:
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parser_errposition(defel->location)));
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fc->colexpr = defel->arg;
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}
14233-
else if (strcmp(defel->defname, "is_not_null") == 0)
14233+
else if (strcmp(defel->defname, "__pg__is_not_null") == 0)
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{
1423514235
if (nullability_seen)
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ereport(ERROR,
@@ -14273,13 +14273,20 @@ xmltable_column_option_list:
1427314273

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xmltable_column_option_el:
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IDENT b_expr
14276-
{ $$ = makeDefElem($1, $2, @1); }
14276+
{
14277+
if (strcmp($1, "__pg__is_not_null") == 0)
14278+
ereport(ERROR,
14279+
(errcode(ERRCODE_SYNTAX_ERROR),
14280+
errmsg("option name \"%s\" cannot be used in XMLTABLE", $1),
14281+
parser_errposition(@1)));
14282+
$$ = makeDefElem($1, $2, @1);
14283+
}
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| DEFAULT b_expr
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{ $$ = makeDefElem("default", $2, @1); }
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| NOT NULL_P
14280-
{ $$ = makeDefElem("is_not_null", (Node *) makeBoolean(true), @1); }
14287+
{ $$ = makeDefElem("__pg__is_not_null", (Node *) makeBoolean(true), @1); }
1428114288
| NULL_P
14282-
{ $$ = makeDefElem("is_not_null", (Node *) makeBoolean(false), @1); }
14289+
{ $$ = makeDefElem("__pg__is_not_null", (Node *) makeBoolean(false), @1); }
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| PATH b_expr
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{ $$ = makeDefElem("path", $2, @1); }
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;

‎src/test/regress/expected/xml.out

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1373,6 +1373,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
13731373
-- errors
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SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
13751375
ERROR: XMLTABLE function has 1 columns available but 2 columns specified
1376+
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
1377+
ERROR: option name "__pg__is_not_null" cannot be used in XMLTABLE
1378+
LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
1379+
^
13761380
-- XMLNAMESPACES tests
13771381
SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
13781382
'/zz:rows/zz:row'

‎src/test/regress/expected/xml_1.out

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1047,6 +1047,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
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-- errors
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SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
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ERROR: XMLTABLE function has 1 columns available but 2 columns specified
1050+
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
1051+
ERROR: option name "__pg__is_not_null" cannot be used in XMLTABLE
1052+
LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
1053+
^
10501054
-- XMLNAMESPACES tests
10511055
SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
10521056
'/zz:rows/zz:row'

‎src/test/regress/expected/xml_2.out

Lines changed: 4 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -1359,6 +1359,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
13591359
-- errors
13601360
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
13611361
ERROR: XMLTABLE function has 1 columns available but 2 columns specified
1362+
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
1363+
ERROR: option name "__pg__is_not_null" cannot be used in XMLTABLE
1364+
LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
1365+
^
13621366
-- XMLNAMESPACES tests
13631367
SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
13641368
'/zz:rows/zz:row'

‎src/test/regress/sql/xml.sql

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -435,6 +435,8 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
435435
-- errors
436436
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
437437

438+
SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
439+
438440
-- XMLNAMESPACES tests
439441
SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
440442
'/zz:rows/zz:row'

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