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

diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 8379e48c97b1c7d6372df464dfb959bfa2f4f532..c77060c2cea8242a26a7043acabebb5af5064361 100644 (file)
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -13820,7 +13820,7 @@ 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,
@@ -13863,13 +13863,20 @@ 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); }
                ;
 
 xml_namespace_list:

diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out
index f9b7ec0bab8d49cbb8c4ba6f1974c66628eb1526..79054b753114b7acead32d6cc5fd3668f0e589eb 100644 (file)
--- a/src/test/regress/expected/xml.out
+++ b/src/test/regress/expected/xml.out
@@ -1139,6 +1139,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
 -- errors
 SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
 ERROR:  XMLTABLE function has 1 columns available but 2 columns specified
+SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
+ERROR:  option name "__pg__is_not_null" cannot be used in XMLTABLE
+LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
+                                                             ^
 -- XMLNAMESPACES tests
 SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
                       '/zz:rows/zz:row'

diff --git a/src/test/regress/expected/xml_1.out b/src/test/regress/expected/xml_1.out
index 5b28ea01eeafb84009c7e58d6475175a76847b84..abf27626a215ed7f40cad7a73667e572d410f7b9 100644 (file)
--- a/src/test/regress/expected/xml_1.out
+++ b/src/test/regress/expected/xml_1.out
@@ -876,6 +876,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
 -- errors
 SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
 ERROR:  XMLTABLE function has 1 columns available but 2 columns specified
+SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
+ERROR:  option name "__pg__is_not_null" cannot be used in XMLTABLE
+LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
+                                                             ^
 -- XMLNAMESPACES tests
 SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
                       '/zz:rows/zz:row'

diff --git a/src/test/regress/expected/xml_2.out b/src/test/regress/expected/xml_2.out
index 044a4917d86c1b24e88904be07fc376d0a8e04a3..23e0c14a2d228a3e5d505ba624c2fa67fd800e14 100644 (file)
--- a/src/test/regress/expected/xml_2.out
+++ b/src/test/regress/expected/xml_2.out
@@ -1125,6 +1125,10 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
 -- errors
 SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
 ERROR:  XMLTABLE function has 1 columns available but 2 columns specified
+SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
+ERROR:  option name "__pg__is_not_null" cannot be used in XMLTABLE
+LINE 1: ...MLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_n...
+                                                             ^
 -- XMLNAMESPACES tests
 SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
                       '/zz:rows/zz:row'

diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql
index e908b6c39572d1fce7967fa42c0305a58c43d18d..83c5b73d8d3e469ec983535a4b84ee6438cde3a8 100644 (file)
--- a/src/test/regress/sql/xml.sql
+++ b/src/test/regress/sql/xml.sql
@@ -387,6 +387,8 @@ EXPLAIN (COSTS OFF, VERBOSE) SELECT * FROM xmltableview1;
 -- errors
 SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp) AS f (v1, v2);
 
+SELECT * FROM XMLTABLE (ROW () PASSING null COLUMNS v1 timestamp __pg__is_not_null 1) AS f (v1);
+
 -- XMLNAMESPACES tests
 SELECT * FROM XMLTABLE(XMLNAMESPACES('http://x.y' AS zz),
                       '/zz:rows/zz:row'