3 files changed, 90 insertions, 1 deletions

diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 5d8eb29f247..390933b0366 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -89,6 +89,8 @@ 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,
@@ -3034,7 +3036,7 @@ ExecBRUpdateTriggers(EState *estate, EPQState *epqstate,
 				ExecCopySlot(newslot, epqslot_clean);
 		}
 
-		trigtuple = ExecFetchSlotHeapTuple(oldslot, true, &should_free_trig);
+		trigtuple = MaterializeTupleForTrigger(oldslot, &should_free_trig);
 	}
 	else
 	{
@@ -3286,6 +3288,9 @@ ExecASTruncateTriggers(EState *estate, ResultRelInfo *relinfo)
 }
 
 
+/*
+ * Fetch tuple into "oldslot", dealing with locking and EPQ if necessary
+ */
 static bool
 GetTupleForTrigger(EState *estate,
 				   EPQState *epqstate,
@@ -3400,6 +3405,40 @@ GetTupleForTrigger(EState *estate,
 }
 
 /*
+ * 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?
  */
 static bool
diff --git a/src/test/regress/expected/triggers.out b/src/test/regress/expected/triggers.out
index 440e8e10784..b2f6d9e27e6 100644
--- a/src/test/regress/expected/triggers.out
+++ b/src/test/regress/expected/triggers.out
@@ -215,6 +215,38 @@ 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 (
 	price_id	int4,
diff --git a/src/test/regress/sql/triggers.sql b/src/test/regress/sql/triggers.sql
index 67eb8ad0416..abf91f23f5e 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 (