Don't crash on reference to an un-available system column.

Adopt a more consistent policy about what slot-type-specific
getsysattr functions should do when system attributes are not
available.  To wit, they should all throw the same user-oriented
error, rather than variously crashing or emitting developer-oriented
messages.

This closes a identifiable problem in commits a71cfc56b and
3fb93103a (in v13 and v12), so back-patch into those branches,
along with a test case to try to ensure we don't break it again.
It is not known that any of the former crash cases are reachable
in HEAD, but this seems like a good safety improvement in any case.

Discussion: https://postgr.es/m/141051591267657@mail.yandex.ru

2 files changed, 85 insertions, 0 deletions

diff --git a/src/test/regress/expected/update.out b/src/test/regress/expected/update.out
index ad91e5aedb8..bbf6705b656 100644
--- a/src/test/regress/expected/update.out
+++ b/src/test/regress/expected/update.out
@@ -795,6 +795,59 @@ DETAIL:  Failing row contains (a, 10).
 -- ok
 UPDATE list_default set a = 'x' WHERE a = 'd';
 DROP TABLE list_parted;
+-- Test retrieval of system columns with non-consistent partition row types.
+-- This is only partially supported, as seen in the results.
+create table utrtest (a int, b text) partition by list (a);
+create table utr1 (a int check (a in (1)), q text, b text);
+create table utr2 (a int check (a in (2)), b text);
+alter table utr1 drop column q;
+alter table utrtest attach partition utr1 for values in (1);
+alter table utrtest attach partition utr2 for values in (2);
+insert into utrtest values (1, 'foo')
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;
+ a |  b  | tableoid | xmin_ok 
+---+-----+----------+---------
+ 1 | foo | utr1     | t
+(1 row)
+
+insert into utrtest values (2, 'bar')
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;  -- fails
+ERROR:  cannot retrieve a system column in this context
+insert into utrtest values (2, 'bar')
+  returning *, tableoid::regclass;
+ a |  b  | tableoid 
+---+-----+----------
+ 2 | bar | utr2
+(1 row)
+
+update utrtest set b = b || b from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;
+ a |   b    | x | tableoid | xmin_ok 
+---+--------+---+----------+---------
+ 1 | foofoo | 1 | utr1     | t
+ 2 | barbar | 2 | utr2     | t
+(2 rows)
+
+update utrtest set a = 3 - a from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;  -- fails
+ERROR:  cannot retrieve a system column in this context
+update utrtest set a = 3 - a from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass;
+ a |   b    | x | tableoid 
+---+--------+---+----------
+ 2 | foofoo | 1 | utr2
+ 1 | barbar | 2 | utr1
+(2 rows)
+
+delete from utrtest
+  returning *, tableoid::regclass, xmax = pg_current_xact_id()::xid as xmax_ok;
+ a |   b    | tableoid | xmax_ok 
+---+--------+----------+---------
+ 1 | barbar | utr1     | t
+ 2 | foofoo | utr2     | t
+(2 rows)
+
+drop table utrtest;
 --------------
 -- Some more update-partition-key test scenarios below. This time use list
 -- partitions.
diff --git a/src/test/regress/sql/update.sql b/src/test/regress/sql/update.sql
index 8c558a7bc72..d0bc8e9228b 100644
--- a/src/test/regress/sql/update.sql
+++ b/src/test/regress/sql/update.sql
@@ -502,6 +502,38 @@ UPDATE list_default set a = 'x' WHERE a = 'd';
 
 DROP TABLE list_parted;
 
+-- Test retrieval of system columns with non-consistent partition row types.
+-- This is only partially supported, as seen in the results.
+
+create table utrtest (a int, b text) partition by list (a);
+create table utr1 (a int check (a in (1)), q text, b text);
+create table utr2 (a int check (a in (2)), b text);
+alter table utr1 drop column q;
+alter table utrtest attach partition utr1 for values in (1);
+alter table utrtest attach partition utr2 for values in (2);
+
+insert into utrtest values (1, 'foo')
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;
+insert into utrtest values (2, 'bar')
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;  -- fails
+insert into utrtest values (2, 'bar')
+  returning *, tableoid::regclass;
+
+update utrtest set b = b || b from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;
+
+update utrtest set a = 3 - a from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass, xmin = pg_current_xact_id()::xid as xmin_ok;  -- fails
+
+update utrtest set a = 3 - a from (values (1), (2)) s(x) where a = s.x
+  returning *, tableoid::regclass;
+
+delete from utrtest
+  returning *, tableoid::regclass, xmax = pg_current_xact_id()::xid as xmax_ok;
+
+drop table utrtest;
+
+
 --------------
 -- Some more update-partition-key test scenarios below. This time use list
 -- partitions.