Fix tupdesc lifespan bug with AfterTriggersTableData.storeslot.

Commit 25936fd46 adjusted things so that the "storeslot" we use
for remapping trigger tuples would have adequate lifespan, but it
neglected to consider the lifespan of the tuple descriptor that
the slot depends on.  It turns out that in at least some cases, the
tupdesc we are passing is a refcounted tupdesc, and the refcount for
the slot's reference can get assigned to a resource owner having
different lifespan than the slot does.  That leads to an error like
"tupdesc reference 0x7fdef236a1b8 is not owned by resource owner
SubTransaction".  Worse, because of a second oversight in the same
commit, we'd try to free the same tupdesc refcount again while
cleaning up after that error, leading to recursive errors and an
"ERRORDATA_STACK_SIZE exceeded" PANIC.

To fix the initial problem, let's just make a non-refcounted copy
of the tupdesc we're supposed to use.  That seems likely to guard
against additional problems, since there's no strong reason for
this code to assume that what it's given is a refcounted tupdesc;
in which case there's an independent hazard of the tupdesc having
shorter lifespan than the slot does.  (I didn't bother trying to
free said copy, since it should go away anyway when the (sub)
transaction context is cleaned up.)

The other issue can be fixed by making the code added to
AfterTriggerFreeQuery work like the rest of that function, ie be
sure that it doesn't try to free the same slot twice in the event
of recursive error cleanup.

While here, also clean up minor stylistic issues in the test case
added by 25936fd46: don't use "create or replace function", as any
name collision within the tests is likely to have ill effects
that that won't mask; and don't use function names as generic as
trigger_function1, especially if you're not going to drop them
at the end of the test stanza.

Per bug #17607 from Thomas Mc Kay.  Back-patch to v12, as the
previous fix was.

Discussion: https://postgr.es/m/17607-bd8ccc81226f7f80@postgresql.org

src/backend/commands/trigger.c

@@ -4775,11 +4775,13 @@ GetAfterTriggersStoreSlot(AfterTriggersTableData *table,
 		MemoryContext oldcxt;
 
 		/*
-		 * We only need this slot only until AfterTriggerEndQuery, but making
-		 * it last till end-of-subxact is good enough.  It'll be freed by
-		 * AfterTriggerFreeQuery().
+		 * We need this slot only until AfterTriggerEndQuery, but making it
+		 * last till end-of-subxact is good enough.  It'll be freed by
+		 * AfterTriggerFreeQuery().  However, the passed-in tupdesc might have
+		 * a different lifespan, so we'd better make a copy of that.
 		 */
 		oldcxt = MemoryContextSwitchTo(CurTransactionContext);
+		tupdesc = CreateTupleDescCopy(tupdesc);
 		table->storeslot = MakeSingleTupleTableSlot(tupdesc, &TTSOpsVirtual);
 		MemoryContextSwitchTo(oldcxt);
 	}
@@ -5098,7 +5100,12 @@ AfterTriggerFreeQuery(AfterTriggersQueryData *qs)
 		if (ts)
 			tuplestore_end(ts);
 		if (table->storeslot)
-			ExecDropSingleTupleTableSlot(table->storeslot);
+		{
+			TupleTableSlot *slot = table->storeslot;
+
+			table->storeslot = NULL;
+			ExecDropSingleTupleTableSlot(slot);
+		}
 	}
 
 	/*

src/test/regress/expected/triggers.out

@@ -3468,7 +3468,7 @@ insert into convslot_test_parent(col1) values ('1');
 insert into convslot_test_child(col1) values ('1');
 insert into convslot_test_parent(col1) values ('3');
 insert into convslot_test_child(col1) values ('3');
-create or replace function trigger_function1()
+create function convslot_trig1()
 returns trigger
 language plpgsql
 AS $$
@@ -3478,7 +3478,7 @@ raise notice 'trigger = %, old_table = %',
           (select string_agg(old_table::text, ', ' order by col1) from old_table);
 return null;
 end; $$;
-create or replace function trigger_function2()
+create function convslot_trig2()
 returns trigger
 language plpgsql
 AS $$
@@ -3490,10 +3490,10 @@ return null;
 end; $$;
 create trigger but_trigger after update on convslot_test_child
 referencing new table as new_table
-for each statement execute function trigger_function2();
+for each statement execute function convslot_trig2();
 update convslot_test_parent set col1 = col1 || '1';
 NOTICE:  trigger = but_trigger, new table = (11,tutu), (31,tutu)
-create or replace function trigger_function3()
+create function convslot_trig3()
 returns trigger
 language plpgsql
 AS $$
@@ -3506,16 +3506,42 @@ return null;
 end; $$;
 create trigger but_trigger2 after update on convslot_test_child
 referencing old table as old_table new table as new_table
-for each statement execute function trigger_function3();
+for each statement execute function convslot_trig3();
 update convslot_test_parent set col1 = col1 || '1';
 NOTICE:  trigger = but_trigger, new table = (111,tutu), (311,tutu)
 NOTICE:  trigger = but_trigger2, old_table = (11,tutu), (31,tutu), new table = (111,tutu), (311,tutu)
 create trigger bdt_trigger after delete on convslot_test_child
 referencing old table as old_table
-for each statement execute function trigger_function1();
+for each statement execute function convslot_trig1();
 delete from convslot_test_parent;
 NOTICE:  trigger = bdt_trigger, old_table = (111,tutu), (311,tutu)
 drop table convslot_test_child, convslot_test_parent;
+drop function convslot_trig1();
+drop function convslot_trig2();
+drop function convslot_trig3();
+-- Bug #17607: variant of above in which trigger function raises an error;
+-- we don't see any ill effects unless trigger tuple requires mapping
+create table convslot_test_parent (id int primary key, val int)
+partition by range (id);
+create table convslot_test_part (val int, id int not null);
+alter table convslot_test_parent
+  attach partition convslot_test_part for values from (1) to (1000);
+create function convslot_trig4() returns trigger as
+$$begin raise exception 'BOOM!'; end$$ language plpgsql;
+create trigger convslot_test_parent_update
+    after update on convslot_test_parent
+    referencing old table as old_rows new table as new_rows
+    for each statement execute procedure convslot_trig4();
+insert into convslot_test_parent (id, val) values (1, 2);
+begin;
+savepoint svp;
+update convslot_test_parent set val = 3;  -- error expected
+ERROR:  BOOM!
+CONTEXT:  PL/pgSQL function convslot_trig4() line 1 at RAISE
+rollback to savepoint svp;
+rollback;
+drop table convslot_test_parent;
+drop function convslot_trig4();
 -- Test trigger renaming on partitioned tables
 create table grandparent (id int, primary key (id)) partition by range (id);
 create table middle partition of grandparent for values from (1) to (10)

src/test/regress/sql/triggers.sql

@@ -2615,7 +2615,7 @@ insert into convslot_test_child(col1) values ('1');
 insert into convslot_test_parent(col1) values ('3');
 insert into convslot_test_child(col1) values ('3');
 
-create or replace function trigger_function1()
+create function convslot_trig1()
 returns trigger
 language plpgsql
 AS $$
@@ -2626,7 +2626,7 @@ raise notice 'trigger = %, old_table = %',
 return null;
 end; $$;
 
-create or replace function trigger_function2()
+create function convslot_trig2()
 returns trigger
 language plpgsql
 AS $$
@@ -2639,11 +2639,11 @@ end; $$;
 
 create trigger but_trigger after update on convslot_test_child
 referencing new table as new_table
-for each statement execute function trigger_function2();
+for each statement execute function convslot_trig2();
 
 update convslot_test_parent set col1 = col1 || '1';
 
-create or replace function trigger_function3()
+create function convslot_trig3()
 returns trigger
 language plpgsql
 AS $$
@@ -2657,15 +2657,48 @@ end; $$;
 
 create trigger but_trigger2 after update on convslot_test_child
 referencing old table as old_table new table as new_table
-for each statement execute function trigger_function3();
+for each statement execute function convslot_trig3();
 update convslot_test_parent set col1 = col1 || '1';
 
 create trigger bdt_trigger after delete on convslot_test_child
 referencing old table as old_table
-for each statement execute function trigger_function1();
+for each statement execute function convslot_trig1();
 delete from convslot_test_parent;
 
 drop table convslot_test_child, convslot_test_parent;
+drop function convslot_trig1();
+drop function convslot_trig2();
+drop function convslot_trig3();
+
+-- Bug #17607: variant of above in which trigger function raises an error;
+-- we don't see any ill effects unless trigger tuple requires mapping
+
+create table convslot_test_parent (id int primary key, val int)
+partition by range (id);
+
+create table convslot_test_part (val int, id int not null);
+
+alter table convslot_test_parent
+  attach partition convslot_test_part for values from (1) to (1000);
+
+create function convslot_trig4() returns trigger as
+$$begin raise exception 'BOOM!'; end$$ language plpgsql;
+
+create trigger convslot_test_parent_update
+    after update on convslot_test_parent
+    referencing old table as old_rows new table as new_rows
+    for each statement execute procedure convslot_trig4();
+
+insert into convslot_test_parent (id, val) values (1, 2);
+
+begin;
+savepoint svp;
+update convslot_test_parent set val = 3;  -- error expected
+rollback to savepoint svp;
+rollback;
+
+drop table convslot_test_parent;
+drop function convslot_trig4();
 
 -- Test trigger renaming on partitioned tables
 create table grandparent (id int, primary key (id)) partition by range (id);