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Commit25d639e

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Further refine _SPI_execute_plan's rule for atomic execution.
Commit2dc1dea turns out to have been still a brick shy of a load,because CALL statements executing within a plpgsql exception blockcould still pass the wrong snapshot to stable functions within theCALL's argument list. That happened because standard_ProcessUtilityforces isAtomicContext to true if IsTransactionBlock is true, whichit always will be inside a subtransaction. Then ExecuteCallStmtwould think it does not need to push a new snapshot --- but_SPI_execute_plan didn't do so either, since it thought it was innonatomic mode.The best fix for this seems to be for _SPI_execute_plan to operatein atomic execution mode if IsSubTransaction() is true, even when theSPI context as a whole is non-atomic. This makes _SPI_execute_planhave the same rules about when non-atomic execution is allowed as_SPI_commit/_SPI_rollback have about when COMMIT/ROLLBACK are allowed,which seems appropriately symmetric. (If anyone ever tries to allowCOMMIT/ROLLBACK inside a subtransaction, this would all need to berethought ... but I'm unconvinced that such a thing could be logicallyconsistent at all.)For further consistency, also check IsSubTransaction() inSPI_inside_nonatomic_context. That does not matter for itsone present-day caller StartTransaction, which can't be reachedinside a subtransaction. But if any other callers ever arise,they'd presumably want this definition.Per bug #18656 from Alexander Alehin. Back-patch to allsupported branches, like previous fixes in this area.Discussion:https://postgr.es/m/18656-cade1780866ef66c@postgresql.org
1 parent05e982c commit25d639e

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3 files changed

+47
-4
lines changed

3 files changed

+47
-4
lines changed

‎src/backend/executor/spi.c‎

Lines changed: 10 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -335,13 +335,13 @@ _SPI_rollback(bool chain)
335335
MemoryContextoldcontext=CurrentMemoryContext;
336336
SavedTransactionCharacteristicssavetc;
337337

338-
/* seeunder SPI_commit() */
338+
/* seecomments in _SPI_commit() */
339339
if (_SPI_current->atomic)
340340
ereport(ERROR,
341341
(errcode(ERRCODE_INVALID_TRANSACTION_TERMINATION),
342342
errmsg("invalid transaction termination")));
343343

344-
/* seeunder SPI_commit() */
344+
/* seecomments in _SPI_commit() */
345345
if (IsSubTransaction())
346346
ereport(ERROR,
347347
(errcode(ERRCODE_INVALID_TRANSACTION_TERMINATION),
@@ -583,8 +583,11 @@ SPI_inside_nonatomic_context(void)
583583
{
584584
if (_SPI_current==NULL)
585585
return false;/* not in any SPI context at all */
586+
/* these tests must match _SPI_commit's opinion of what's atomic: */
586587
if (_SPI_current->atomic)
587588
return false;/* it's atomic (ie function not procedure) */
589+
if (IsSubTransaction())
590+
return false;/* if within subtransaction, it's atomic */
588591
return true;
589592
}
590593

@@ -2410,9 +2413,12 @@ _SPI_execute_plan(SPIPlanPtr plan, const SPIExecuteOptions *options,
24102413

24112414
/*
24122415
* We allow nonatomic behavior only if options->allow_nonatomic is set
2413-
* *and* the SPI_OPT_NONATOMIC flag was given when connecting.
2416+
* *and* the SPI_OPT_NONATOMIC flag was given when connecting and we are
2417+
* not inside a subtransaction. The latter two tests match whether
2418+
* _SPI_commit() would allow a commit; see there for more commentary.
24142419
*/
2415-
allow_nonatomic=options->allow_nonatomic&& !_SPI_current->atomic;
2420+
allow_nonatomic=options->allow_nonatomic&&
2421+
!_SPI_current->atomic&& !IsSubTransaction();
24162422

24172423
/*
24182424
* Setup error traceback support for ereport()

‎src/pl/plpgsql/src/expected/plpgsql_call.out‎

Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -597,6 +597,26 @@ NOTICE: f_get_x(1)
597597
NOTICE: f_print_x(1)
598598
NOTICE: f_get_x(2)
599599
NOTICE: f_print_x(2)
600+
-- test in non-atomic context, except exception block is locally atomic
601+
DO $$
602+
BEGIN
603+
BEGIN
604+
UPDATE t_test SET x = x + 1;
605+
RAISE NOTICE 'f_get_x(%)', f_get_x();
606+
CALL f_print_x(f_get_x());
607+
UPDATE t_test SET x = x + 1;
608+
RAISE NOTICE 'f_get_x(%)', f_get_x();
609+
CALL f_print_x(f_get_x());
610+
EXCEPTION WHEN division_by_zero THEN
611+
RAISE NOTICE '%', SQLERRM;
612+
END;
613+
ROLLBACK;
614+
END
615+
$$;
616+
NOTICE: f_get_x(1)
617+
NOTICE: f_print_x(1)
618+
NOTICE: f_get_x(2)
619+
NOTICE: f_print_x(2)
600620
-- test in atomic context
601621
BEGIN;
602622
DO $$

‎src/pl/plpgsql/src/sql/plpgsql_call.sql‎

Lines changed: 17 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -557,6 +557,23 @@ BEGIN
557557
END
558558
$$;
559559

560+
-- test in non-atomic context, except exception block is locally atomic
561+
DO $$
562+
BEGIN
563+
BEGIN
564+
UPDATE t_testSET x= x+1;
565+
RAISE NOTICE'f_get_x(%)', f_get_x();
566+
CALL f_print_x(f_get_x());
567+
UPDATE t_testSET x= x+1;
568+
RAISE NOTICE'f_get_x(%)', f_get_x();
569+
CALL f_print_x(f_get_x());
570+
EXCEPTION WHEN division_by_zero THEN
571+
RAISE NOTICE'%', SQLERRM;
572+
END;
573+
ROLLBACK;
574+
END
575+
$$;
576+
560577
-- test in atomic context
561578
BEGIN;
562579

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