Re: BUG #17607: Server process crashes when PLpgSQL function raises error in subtransaction

... and after yet more poking at it, I see why c5b7ba4e6 masked
the problem: it added an optimization such that we don't use the
storeslot at all unless a tuple mapping conversion is required.
That led me to the test case shown in the attached, which exhibits
this symptom in all branches since v12.

I had been planning to let this wait until after 15rc1 wrap,
but now that I have evidence that the bug is still live in v15,
I'm going to go ahead and push.  Both components of the fix
seem like extremely safe changes, even for the day before wrap.

            regards, tom lane

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 0ec8d84a1b..0fcf090f22 100644
--- a/src/backend/commands/trigger.c
+++ b/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);
+        }
     }

     /*
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index 641f5e67c4..8b8eadd181 100644
--- a/src/test/regress/expected/triggers.out
+++ b/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)
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index 9d21bbe2a9..4d8504fb24 100644
--- a/src/test/regress/sql/triggers.sql
+++ b/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);