From d88d8ad28484a745fffe036a4085f4674b3064bc Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Sun, 25 Oct 2020 13:57:46 -0400 Subject: [PATCH] Fix corner case for a BEFORE ROW UPDATE trigger returning OLD. If the old row has any "missing" attributes that are supposed to be retrieved from an associated tuple descriptor, the wrong things happened because the trigger result is shoved directly into an executor slot that lacks the missing-attribute data. Notably, CHECK-constraint verification would incorrectly see those columns as NULL, and so would RETURNING-list evaluation. Band-aid around this by forcibly expanding the tuple before passing it to the trigger function. (IMO it was a fundamental misdesign to put the missing-attribute data into tuple constraints, which so much of the system considers to be optional. But we're probably stuck with that now, and will have to continue to apply band-aids as we find other places with similar issues.) Back-patch to v12. v11 would also have the issue, except that commit 920311ab1 already applied a similar band-aid. That forced expansion in more cases than seem really necessary, though, so this isn't a directly equivalent fix. Amit Langote, with some cosmetic changes by me Discussion: https://postgr.es/m/16644-5da7ef98a7ac4545@postgresql.org --- src/backend/commands/trigger.c | 41 +++++++++++++++++++++++++- src/test/regress/expected/triggers.out | 32 ++++++++++++++++++++ src/test/regress/sql/triggers.sql | 18 +++++++++++ 3 files changed, 90 insertions(+), 1 deletion(-) diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c index bbaa5cdf4b2..d4427917476 100644 --- a/src/backend/commands/trigger.c +++ b/src/backend/commands/trigger.c @@ -88,6 +88,8 @@ static bool GetTupleForTrigger(EState *estate, LockTupleMode lockmode, TupleTableSlot *oldslot, TupleTableSlot **newSlot); +static HeapTuple MaterializeTupleForTrigger(TupleTableSlot *slot, + bool *shouldFree); static bool TriggerEnabled(EState *estate, ResultRelInfo *relinfo, Trigger *trigger, TriggerEvent event, Bitmapset *modifiedCols, @@ -2671,7 +2673,7 @@ ExecBRUpdateTriggers(EState *estate, EPQState *epqstate, ExecCopySlot(newslot, epqslot_clean); } - trigtuple = ExecFetchSlotHeapTuple(oldslot, true, &should_free_trig); + trigtuple = MaterializeTupleForTrigger(oldslot, &should_free_trig); } else { @@ -2924,6 +2926,9 @@ ExecASTruncateTriggers(EState *estate, ResultRelInfo *relinfo) } +/* + * Fetch tuple into "oldslot", dealing with locking and EPQ if necessary + */ static bool GetTupleForTrigger(EState *estate, EPQState *epqstate, @@ -3037,6 +3042,40 @@ GetTupleForTrigger(EState *estate, return true; } +/* + * Extract a HeapTuple that we can pass off to trigger functions. + * + * We must materialize the tuple and make sure it is not dependent on any + * attrmissing data. This is needed for the old row in BEFORE UPDATE + * triggers, since they can choose to pass back this exact tuple as the update + * result, causing the tuple to be inserted into an executor slot that lacks + * the attrmissing data. + * + * Currently we don't seem to need to remove the attrmissing dependency in any + * other cases, but keep this as a separate function to simplify fixing things + * if that changes. + */ +static HeapTuple +MaterializeTupleForTrigger(TupleTableSlot *slot, bool *shouldFree) +{ + HeapTuple tup; + TupleDesc tupdesc = slot->tts_tupleDescriptor; + + tup = ExecFetchSlotHeapTuple(slot, true, shouldFree); + if (HeapTupleHeaderGetNatts(tup->t_data) < tupdesc->natts && + tupdesc->constr && tupdesc->constr->missing) + { + HeapTuple newtup; + + newtup = heap_expand_tuple(tup, tupdesc); + if (*shouldFree) + heap_freetuple(tup); + *shouldFree = true; + tup = newtup; + } + return tup; +} + /* * Is trigger enabled to fire? */ diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out index 57efa290207..c19aac96742 100644 --- a/src/test/regress/expected/triggers.out +++ b/src/test/regress/expected/triggers.out @@ -214,6 +214,38 @@ select * from trigtest; ----+---- (0 rows) +drop table trigtest; +-- Check behavior with an implicit column default, too (bug #16644) +create table trigtest (a integer); +create trigger trigger_return_old + before insert or delete or update on trigtest + for each row execute procedure trigger_return_old(); +insert into trigtest values(1); +select * from trigtest; + a +--- + 1 +(1 row) + +alter table trigtest add column b integer default 42 not null; +select * from trigtest; + a | b +---+---- + 1 | 42 +(1 row) + +update trigtest set a = 2 where a = 1 returning *; + a | b +---+---- + 1 | 42 +(1 row) + +select * from trigtest; + a | b +---+---- + 1 | 42 +(1 row) + drop table trigtest; create sequence ttdummy_seq increment 10 start 0 minvalue 0; create table tttest ( diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql index 8f66df9f3b4..bf2e73abf60 100644 --- a/src/test/regress/sql/triggers.sql +++ b/src/test/regress/sql/triggers.sql @@ -154,6 +154,24 @@ select * from trigtest; drop table trigtest; +-- Check behavior with an implicit column default, too (bug #16644) +create table trigtest (a integer); + +create trigger trigger_return_old + before insert or delete or update on trigtest + for each row execute procedure trigger_return_old(); + +insert into trigtest values(1); +select * from trigtest; + +alter table trigtest add column b integer default 42 not null; + +select * from trigtest; +update trigtest set a = 2 where a = 1 returning *; +select * from trigtest; + +drop table trigtest; + create sequence ttdummy_seq increment 10 start 0 minvalue 0; create table tttest (