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

diff --git a/src/backend/executor/execTuples.c b/src/backend/executor/execTuples.c
index 73c35df9c9686db3ac5171ae39905189cc6b10ba..f4478028431f031fc16535b917e0498fd16f514d 100644 (file)
--- a/src/backend/executor/execTuples.c
+++ b/src/backend/executor/execTuples.c
@@ -122,9 +122,8 @@ tts_virtual_clear(TupleTableSlot *slot)
 }
 
 /*
- * Attribute values are readily available in tts_values and tts_isnull array
- * in a VirtualTupleTableSlot. So there should be no need to call either of the
- * following two functions.
+ * VirtualTupleTableSlots always have fully populated tts_values and
+ * tts_isnull arrays.  So this function should never be called.
  */
 static void
 tts_virtual_getsomeattrs(TupleTableSlot *slot, int natts)
@@ -132,10 +131,19 @@ tts_virtual_getsomeattrs(TupleTableSlot *slot, int natts)
    elog(ERROR, "getsomeattrs is not required to be called on a virtual tuple table slot");
 }
 
+/*
+ * VirtualTupleTableSlots never provide system attributes (except those
+ * handled generically, such as tableoid).  We generally shouldn't get
+ * here, but provide a user-friendly message if we do.
+ */
 static Datum
 tts_virtual_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
 {
-   elog(ERROR, "virtual tuple table slot does not have system attributes");
+   Assert(!TTS_EMPTY(slot));
+
+   ereport(ERROR,
+           (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+            errmsg("cannot retrieve a system column in this context")));
 
    return 0;                   /* silence compiler warnings */
 }
@@ -335,6 +343,15 @@ tts_heap_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
 
    Assert(!TTS_EMPTY(slot));
 
+   /*
+    * In some code paths it's possible to get here with a non-materialized
+    * slot, in which case we can't retrieve system columns.
+    */
+   if (!hslot->tuple)
+       ereport(ERROR,
+               (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                errmsg("cannot retrieve a system column in this context")));
+
    return heap_getsysattr(hslot->tuple, attnum,
                           slot->tts_tupleDescriptor, isnull);
 }
@@ -497,7 +514,11 @@ tts_minimal_getsomeattrs(TupleTableSlot *slot, int natts)
 static Datum
 tts_minimal_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
 {
-   elog(ERROR, "minimal tuple table slot does not have system attributes");
+   Assert(!TTS_EMPTY(slot));
+
+   ereport(ERROR,
+           (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+            errmsg("cannot retrieve a system column in this context")));
 
    return 0;                   /* silence compiler warnings */
 }
@@ -681,6 +702,15 @@ tts_buffer_heap_getsysattr(TupleTableSlot *slot, int attnum, bool *isnull)
 
    Assert(!TTS_EMPTY(slot));
 
+   /*
+    * In some code paths it's possible to get here with a non-materialized
+    * slot, in which case we can't retrieve system columns.
+    */
+   if (!bslot->base.tuple)
+       ereport(ERROR,
+               (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                errmsg("cannot retrieve a system column in this context")));
+
    return heap_getsysattr(bslot->base.tuple, attnum,
                           slot->tts_tupleDescriptor, isnull);
 }

diff --git a/src/test/regress/expected/update.out b/src/test/regress/expected/update.out
index ad91e5aedb871e971814edd99fb68f2000bf4cef..bbf6705b656c095388f7cdef60be867d8fb33f50 100644 (file)
--- 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 8c558a7bc7286f01331fbf97236e97c08ed9e622..d0bc8e9228bac263ec7399d09b42c613fc3ca163 100644 (file)
--- 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.