Fast default trigger and expand_tuple fixes

Ensure that triggers get properly filled in tuples for the OLD value.
Also fix the logic of detecting missing null values. The previous logic
failed to detect a missing null column before the first missing column
with a default. Fixing this has simplified the logic a bit.

Regression tests are added to test changes. This should ensure better
coverage of expand_tuple().

Original bug reports, and some code and test scripts from Tomas Vondra

Backpatch to release 11.

4 files changed, 328 insertions, 33 deletions

diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index 2ec7e6a4392..efe4ac0e7dc 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -823,44 +823,35 @@ expand_tuple(HeapTuple *targetHeapTuple,
 		{
 			if (attrmiss[firstmissingnum].am_present)
 				break;
+			else
+				hasNulls = true;
 		}
 
 		/*
-		 * If there are no more missing values everything else must be NULL
+		 * Now walk the missing attributes. If there is a missing value
+		 * make space for it. Otherwise, it's going to be NULL.
 		 */
-		if (firstmissingnum >= natts)
-		{
-			hasNulls = true;
-		}
-		else
+		for (attnum = firstmissingnum;
+			 attnum < natts;
+			 attnum++)
 		{
-
-			/*
-			 * Now walk the missing attributes. If there is a missing value
-			 * make space for it. Otherwise, it's going to be NULL.
-			 */
-			for (attnum = firstmissingnum;
-				 attnum < natts;
-				 attnum++)
+			if (attrmiss[attnum].am_present)
 			{
-				if (attrmiss[attnum].am_present)
-				{
-					Form_pg_attribute att = TupleDescAttr(tupleDesc, attnum);
+				Form_pg_attribute att = TupleDescAttr(tupleDesc, attnum);
 
-					targetDataLen = att_align_datum(targetDataLen,
-													att->attalign,
-													att->attlen,
-													attrmiss[attnum].am_value);
+				targetDataLen = att_align_datum(targetDataLen,
+												att->attalign,
+												att->attlen,
+												attrmiss[attnum].am_value);
 
-					targetDataLen = att_addlength_pointer(targetDataLen,
-														  att->attlen,
-														  attrmiss[attnum].am_value);
-				}
-				else
-				{
-					/* no missing value, so it must be null */
-					hasNulls = true;
-				}
+				targetDataLen = att_addlength_pointer(targetDataLen,
+													  att->attlen,
+													  attrmiss[attnum].am_value);
+			}
+			else
+			{
+				/* no missing value, so it must be null */
+				hasNulls = true;
 			}
 		}
 	}							/* end if have missing values */
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 2436692eb85..0665f110ba3 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -3396,7 +3396,10 @@ ltrmark:;
 		LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
 	}
 
-	result = heap_copytuple(&tuple);
+	if (HeapTupleHeaderGetNatts(tuple.t_data) < relation->rd_att->natts)
+		result = heap_expand_tuple(&tuple, relation->rd_att);
+	else
+		result = heap_copytuple(&tuple);
 	ReleaseBuffer(buffer);
 
 	return result;
diff --git a/src/test/regress/expected/fast_default.out b/src/test/regress/expected/fast_default.out
index f3d783c2813..48bd360a799 100644
--- a/src/test/regress/expected/fast_default.out
+++ b/src/test/regress/expected/fast_default.out
@@ -539,8 +539,197 @@ FROM t1;
  1 | 0
 (20 rows)
 
-DROP TABLE t1;
 DROP TABLE T;
+-- test that we account for missing columns without defaults correctly
+-- in expand_tuple, and that rows are correctly expanded for triggers
+CREATE FUNCTION test_trigger()
+RETURNS trigger
+LANGUAGE plpgsql
+AS $$
+
+begin
+    raise notice 'old tuple: %', to_json(OLD)::text;
+    if TG_OP = 'DELETE'
+    then
+       return OLD;
+    else
+       return NEW;
+    end if;
+end;
+
+$$;
+-- 2 new columns, both have defaults
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 | 4 | 5
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":3,"x":4,"y":5}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 | 4 | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, first has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 | 4 |  
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":3,"x":4,"y":null}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 | 4 | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, second has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 |   | 5
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":3,"x":null,"y":5}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 |   | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, neither has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 |   |  
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":3,"x":null,"y":null}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 | 3 |   | 2
+(1 row)
+
+DROP TABLE t;
+-- same as last 4 tests but here the last original column has a NULL value
+-- 2 new columns, both have defaults
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   | 4 | 5
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":null,"x":4,"y":5}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   | 4 | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, first has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   | 4 |  
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":null,"x":4,"y":null}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   | 4 | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, second has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   |   | 5
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":null,"x":null,"y":5}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   |   | 2
+(1 row)
+
+DROP TABLE t;
+-- 2 new columns, neither has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   |   |  
+(1 row)
+
+UPDATE t SET y = 2;
+NOTICE:  old tuple: {"id":1,"a":1,"b":2,"c":null,"x":null,"y":null}
+SELECT * FROM t;
+ id | a | b | c | x | y 
+----+---+---+---+---+---
+  1 | 1 | 2 |   |   | 2
+(1 row)
+
+DROP TABLE t;
+-- cleanup
+DROP FUNCTION test_trigger();
+DROP TABLE t1;
 DROP FUNCTION set(name);
 DROP FUNCTION comp();
 DROP TABLE m;
diff --git a/src/test/regress/sql/fast_default.sql b/src/test/regress/sql/fast_default.sql
index 7b9cc47cef5..06205cb39f0 100644
--- a/src/test/regress/sql/fast_default.sql
+++ b/src/test/regress/sql/fast_default.sql
@@ -360,8 +360,120 @@ SELECT a,
        AS z
 FROM t1;
 
-DROP TABLE t1;
 DROP TABLE T;
+
+-- test that we account for missing columns without defaults correctly
+-- in expand_tuple, and that rows are correctly expanded for triggers
+
+CREATE FUNCTION test_trigger()
+RETURNS trigger
+LANGUAGE plpgsql
+AS $$
+
+begin
+    raise notice 'old tuple: %', to_json(OLD)::text;
+    if TG_OP = 'DELETE'
+    then
+       return OLD;
+    else
+       return NEW;
+    end if;
+end;
+
+$$;
+
+-- 2 new columns, both have defaults
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, first has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, second has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, neither has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,3);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- same as last 4 tests but here the last original column has a NULL value
+-- 2 new columns, both have defaults
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, first has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int NOT NULL DEFAULT 4;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, second has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int NOT NULL DEFAULT 5;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- 2 new columns, neither has default
+CREATE TABLE t (id serial PRIMARY KEY, a int, b int, c int);
+INSERT INTO t (a,b,c) VALUES (1,2,NULL);
+ALTER TABLE t ADD COLUMN x int;
+ALTER TABLE t ADD COLUMN y int;
+CREATE TRIGGER a BEFORE UPDATE ON t FOR EACH ROW EXECUTE PROCEDURE test_trigger();
+SELECT * FROM t;
+UPDATE t SET y = 2;
+SELECT * FROM t;
+DROP TABLE t;
+
+-- cleanup
+DROP FUNCTION test_trigger();
+DROP TABLE t1;
 DROP FUNCTION set(name);
 DROP FUNCTION comp();
 DROP TABLE m;