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Commitabe60b6

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Don't corrupt plpython's "TD" dictionary in a recursive trigger call.
If a plpython-language trigger caused another one to be invoked,the "TD" dictionary created for the inner one would overwrite theouter one's "TD" dictionary. This is more or less the same problemthat1d2fe56 fixed for ordinary functions in plpython, so fix itthe same way, by saving and restoring "TD" during a recursiveinvocation.This fix makes an ABI-incompatible change in struct PLySavedArgs.I'm not too worried about that because it seems highly unlikely thatany extension is messing with those structs. We could imagine doingsomething weird to preserve nominal ABI compatibility in the backbranches, like keeping the saved TD object in an extra element ofnamedargs[]. However, that would only be very nominal compatibility:if anything *is* touching PLySavedArgs, it would likely do the wrongthing due to not knowing about the additional value. So I judge itnot worth the ugliness to do something different there.(I also changed struct PLyProcedure, but its added field fitsinto formerly-padding space, so that should be safe.)Per bug #18456 from Jacques Combrink. This bug is very ancient,so back-patch to all supported branches.Discussion:https://postgr.es/m/3008982.1714853799@sss.pgh.pa.us
1 parent8e5faba commitabe60b6

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5 files changed

+80
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‎src/pl/plpython/expected/plpython_trigger.out

Lines changed: 27 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -618,3 +618,30 @@ SELECT * FROM trigger_test_generated;
618618
---+---
619619
(0 rows)
620620

621+
-- recursive call of a trigger mustn't corrupt TD (bug #18456)
622+
CREATE TABLE recursive_trigger_test (a int, b int);
623+
CREATE FUNCTION recursive_trigger_func() RETURNS trigger
624+
LANGUAGE plpythonu
625+
AS $$
626+
if TD["event"] == "UPDATE":
627+
plpy.execute("INSERT INTO recursive_trigger_test VALUES (1, 2)")
628+
plpy.notice("TD[event] => " + str(TD["event"]) + ", expecting UPDATE");
629+
else:
630+
plpy.notice("TD[event] => " + str(TD["event"]) + ", expecting INSERT");
631+
return None
632+
$$;
633+
CREATE TRIGGER recursive_trigger_trig
634+
AFTER INSERT OR UPDATE ON recursive_trigger_test
635+
FOR EACH ROW EXECUTE PROCEDURE recursive_trigger_func();
636+
INSERT INTO recursive_trigger_test VALUES (0, 0);
637+
NOTICE: TD[event] => INSERT, expecting INSERT
638+
UPDATE recursive_trigger_test SET a = 11 WHERE b = 0;
639+
NOTICE: TD[event] => INSERT, expecting INSERT
640+
NOTICE: TD[event] => UPDATE, expecting UPDATE
641+
SELECT * FROM recursive_trigger_test;
642+
a | b
643+
----+---
644+
11 | 0
645+
1 | 2
646+
(2 rows)
647+

‎src/pl/plpython/plpy_exec.c

Lines changed: 26 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -335,6 +335,13 @@ PLy_exec_trigger(FunctionCallInfo fcinfo, PLyProcedure *proc)
335335
PLy_output_setup_tuple(&proc->result,rel_descr,proc);
336336
PLy_input_setup_tuple(&proc->result_in,rel_descr,proc);
337337

338+
/*
339+
* If the trigger is called recursively, we must push outer-level
340+
* arguments into the stack. This must be immediately before the PG_TRY
341+
* to ensure that the corresponding pop happens.
342+
*/
343+
PLy_global_args_push(proc);
344+
338345
PG_TRY();
339346
{
340347
intrcPG_USED_FOR_ASSERTS_ONLY;
@@ -401,6 +408,7 @@ PLy_exec_trigger(FunctionCallInfo fcinfo, PLyProcedure *proc)
401408
}
402409
PG_FINALLY();
403410
{
411+
PLy_global_args_pop(proc);
404412
Py_XDECREF(plargs);
405413
Py_XDECREF(plrv);
406414
}
@@ -505,6 +513,13 @@ PLy_function_save_args(PLyProcedure *proc)
505513
result->args=PyDict_GetItemString(proc->globals,"args");
506514
Py_XINCREF(result->args);
507515

516+
/* If it's a trigger, also save "TD" */
517+
if (proc->is_trigger)
518+
{
519+
result->td=PyDict_GetItemString(proc->globals,"TD");
520+
Py_XINCREF(result->td);
521+
}
522+
508523
/* Fetch all the named arguments */
509524
if (proc->argnames)
510525
{
@@ -554,6 +569,13 @@ PLy_function_restore_args(PLyProcedure *proc, PLySavedArgs *savedargs)
554569
Py_DECREF(savedargs->args);
555570
}
556571

572+
/* Restore the "TD" object, too */
573+
if (savedargs->td)
574+
{
575+
PyDict_SetItemString(proc->globals,"TD",savedargs->td);
576+
Py_DECREF(savedargs->td);
577+
}
578+
557579
/* And free the PLySavedArgs struct */
558580
pfree(savedargs);
559581
}
@@ -572,8 +594,9 @@ PLy_function_drop_args(PLySavedArgs *savedargs)
572594
Py_XDECREF(savedargs->namedargs[i]);
573595
}
574596

575-
/* Dropref to the "args"object, too */
597+
/* Droprefs to the "args"and "TD" objects, too */
576598
Py_XDECREF(savedargs->args);
599+
Py_XDECREF(savedargs->td);
577600

578601
/* And free the PLySavedArgs struct */
579602
pfree(savedargs);
@@ -582,9 +605,9 @@ PLy_function_drop_args(PLySavedArgs *savedargs)
582605
/*
583606
* Save away any existing arguments for the given procedure, so that we can
584607
* install new values for a recursive call. This should be invoked before
585-
* doing PLy_function_build_args().
608+
* doing PLy_function_build_args() or PLy_trigger_build_args().
586609
*
587-
* NB:caller must ensure that PLy_global_args_pop gets invoked once, and
610+
* NB:callers must ensure that PLy_global_args_pop gets invoked once, and
588611
* only once, per successful completion of PLy_global_args_push. Otherwise
589612
* we'll end up out-of-sync between the actual call stack and the contents
590613
* of proc->argstack.

‎src/pl/plpython/plpy_procedure.c

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -184,6 +184,7 @@ PLy_procedure_create(HeapTuple procTup, Oid fn_oid, bool is_trigger)
184184
proc->fn_readonly= (procStruct->provolatile!=PROVOLATILE_VOLATILE);
185185
proc->is_setof=procStruct->proretset;
186186
proc->is_procedure= (procStruct->prokind==PROKIND_PROCEDURE);
187+
proc->is_trigger=is_trigger;
187188
proc->src=NULL;
188189
proc->argnames=NULL;
189190
proc->args=NULL;

‎src/pl/plpython/plpy_procedure.h

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -16,6 +16,7 @@ typedef struct PLySavedArgs
1616
{
1717
structPLySavedArgs*next;/* linked-list pointer */
1818
PyObject*args;/* "args" element of globals dict */
19+
PyObject*td;/* "TD" element of globals dict, if trigger */
1920
intnargs;/* length of namedargs array */
2021
PyObject*namedargs[FLEXIBLE_ARRAY_MEMBER];/* named args */
2122
}PLySavedArgs;
@@ -32,6 +33,7 @@ typedef struct PLyProcedure
3233
boolfn_readonly;
3334
boolis_setof;/* true, if function returns result set */
3435
boolis_procedure;
36+
boolis_trigger;/* called as trigger? */
3537
PLyObToDatumresult;/* Function result output conversion info */
3638
PLyDatumToObresult_in;/* For converting input tuples in a trigger */
3739
char*src;/* textual procedure code, after mangling */

‎src/pl/plpython/sql/plpython_trigger.sql

Lines changed: 24 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -467,3 +467,27 @@ FOR EACH ROW EXECUTE PROCEDURE generated_test_func1();
467467
TRUNCATE trigger_test_generated;
468468
INSERT INTO trigger_test_generated (i)VALUES (1);
469469
SELECT*FROM trigger_test_generated;
470+
471+
472+
-- recursive call of a trigger mustn't corrupt TD (bug #18456)
473+
474+
CREATETABLErecursive_trigger_test (aint, bint);
475+
476+
CREATEFUNCTIONrecursive_trigger_func() RETURNS trigger
477+
LANGUAGE plpythonu
478+
AS $$
479+
if TD["event"]=="UPDATE":
480+
plpy.execute("INSERT INTO recursive_trigger_test VALUES (1, 2)")
481+
plpy.notice("TD[event] =>"+ str(TD["event"])+", expecting UPDATE");
482+
else:
483+
plpy.notice("TD[event] =>"+ str(TD["event"])+", expecting INSERT");
484+
return None
485+
$$;
486+
487+
CREATETRIGGERrecursive_trigger_trig
488+
AFTER INSERTORUPDATEON recursive_trigger_test
489+
FOR EACH ROW EXECUTE PROCEDURE recursive_trigger_func();
490+
491+
INSERT INTO recursive_trigger_testVALUES (0,0);
492+
UPDATE recursive_trigger_testSET a=11WHERE b=0;
493+
SELECT*FROM recursive_trigger_test;

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