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Fix Assert failure in XMLTABLE parser

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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
This commit is contained in:
Richard Guo
2025-05-15 17:09:04 +09:00
parent 2c0ed86d39
commit fe29b2a1da
5 changed files with 25 additions and 4 deletions
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15
src/backend/parser/gram.y
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@ -14230,7 +14230,7 @@ xmltable_column_el:
parser_errposition(defel->location)));
fc->colexpr = defel->arg;
}
else if (strcmp(defel->defname, "is_not_null") == 0)
else if (strcmp(defel->defname, "__pg__is_not_null") == 0)
{
if (nullability_seen)
ereport(ERROR,
@ -14273,13 +14273,20 @@ xmltable_column_option_list:
xmltable_column_option_el:
IDENT b_expr
{ $$ = makeDefElem($1, $2, @1); }
{
if (strcmp($1, "__pg__is_not_null") == 0)
ereport(ERROR,
(errcode(ERRCODE_SYNTAX_ERROR),
errmsg("option name \"%s\" cannot be used in XMLTABLE", $1),
parser_errposition(@1)));
$$ = makeDefElem($1, $2, @1);
}
| DEFAULT b_expr
{ $$ = makeDefElem("default", $2, @1); }
| NOT NULL_P
{ $$ = makeDefElem("is_not_null", (Node *) makeBoolean(true), @1); }
{ $$ = makeDefElem("__pg__is_not_null", (Node *) makeBoolean(true), @1); }
| NULL_P
{ $$ = makeDefElem("is_not_null", (Node *) makeBoolean(false), @1); }
{ $$ = makeDefElem("__pg__is_not_null", (Node *) makeBoolean(false), @1); }
| PATH b_expr
{ $$ = makeDefElem("path", $2, @1); }
;