Fix application of identity values in some cases

Investigation of 2d2d06b7e2 revealed that
identity values were not applied in some further cases, including
logical replication subscribers, VALUES RTEs, and ALTER TABLE ... ADD
COLUMN.  To fix all that, apply the identity column expression in
build_column_default() instead of repeating the same logic at each call
site.

For ALTER TABLE ... ADD COLUMN ... IDENTITY, the previous coding
completely ignored that existing rows for the new column should have
values filled in from the identity sequence.  The coding using
build_column_default() fails for this because the sequence ownership
isn't registered until after ALTER TABLE, and we can't do it before
because we don't have the column in the catalog yet.  So we specially
remember in ColumnDef the sequence name that we decided on and build a
custom NextValueExpr using that.

Reviewed-by: Michael Paquier <michael.paquier@gmail.com>

src/test/regress/expected/identity.out

@@ -104,6 +104,19 @@ SELECT * FROM itest4;
  2 | 
 (2 rows)
 
+-- VALUES RTEs
+INSERT INTO itest3 VALUES (DEFAULT, 'a');
+INSERT INTO itest3 VALUES (DEFAULT, 'b'), (DEFAULT, 'c');
+SELECT * FROM itest3;
+ a  | b 
+----+---
+  7 | 
+ 12 | 
+ 17 | a
+ 22 | b
+ 27 | c
+(5 rows)
+
 -- OVERRIDING tests
 INSERT INTO itest1 VALUES (10, 'xyz');
 INSERT INTO itest1 OVERRIDING USER VALUE VALUES (10, 'xyz');
@@ -237,6 +250,21 @@ SELECT * FROM itestv11;
  11 | xyz
 (3 rows)
 
+-- ADD COLUMN
+CREATE TABLE itest13 (a int);
+-- add column to empty table
+ALTER TABLE itest13 ADD COLUMN b int GENERATED BY DEFAULT AS IDENTITY;
+INSERT INTO itest13 VALUES (1), (2), (3);
+-- add column to populated table
+ALTER TABLE itest13 ADD COLUMN c int GENERATED BY DEFAULT AS IDENTITY;
+SELECT * FROM itest13;
+ a | b | c 
+---+---+---
+ 1 | 1 | 1
+ 2 | 2 | 2
+ 3 | 3 | 3
+(3 rows)
+
 -- various ALTER COLUMN tests
 -- fail, not allowed for identity columns
 ALTER TABLE itest1 ALTER COLUMN a SET DEFAULT 1;

src/test/regress/sql/identity.sql

@@ -54,6 +54,14 @@ SELECT * FROM itest3;
 SELECT * FROM itest4;
 
 
+-- VALUES RTEs
+
+INSERT INTO itest3 VALUES (DEFAULT, 'a');
+INSERT INTO itest3 VALUES (DEFAULT, 'b'), (DEFAULT, 'c');
+
+SELECT * FROM itest3;
+
+
 -- OVERRIDING tests
 
 INSERT INTO itest1 VALUES (10, 'xyz');
@@ -138,6 +146,17 @@ INSERT INTO itestv11 OVERRIDING SYSTEM VALUE VALUES (11, 'xyz');
 SELECT * FROM itestv11;
 
 
+-- ADD COLUMN
+
+CREATE TABLE itest13 (a int);
+-- add column to empty table
+ALTER TABLE itest13 ADD COLUMN b int GENERATED BY DEFAULT AS IDENTITY;
+INSERT INTO itest13 VALUES (1), (2), (3);
+-- add column to populated table
+ALTER TABLE itest13 ADD COLUMN c int GENERATED BY DEFAULT AS IDENTITY;
+SELECT * FROM itest13;
+
+
 -- various ALTER COLUMN tests
 
 -- fail, not allowed for identity columns

src/test/subscription/t/008_diff_schema.pl

@@ -3,7 +3,7 @@ use strict;
 use warnings;
 use PostgresNode;
 use TestLib;
-use Test::More tests => 3;
+use Test::More tests => 4;
 
 # Create publisher node
 my $node_publisher = get_new_node('publisher');
@@ -22,7 +22,7 @@ $node_publisher->safe_psql('postgres',
 	"INSERT INTO test_tab VALUES (1, 'foo'), (2, 'bar')");
 
 # Setup structure on subscriber
-$node_subscriber->safe_psql('postgres', "CREATE TABLE test_tab (a int primary key, b text, c timestamptz DEFAULT now(), d bigint DEFAULT 999)");
+$node_subscriber->safe_psql('postgres', "CREATE TABLE test_tab (a int primary key, b text, c timestamptz DEFAULT now(), d bigint DEFAULT 999, e int GENERATED BY DEFAULT AS IDENTITY)");
 
 # Setup logical replication
 my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
@@ -52,8 +52,8 @@ $node_publisher->safe_psql('postgres', "UPDATE test_tab SET b = md5(b)");
 $node_publisher->wait_for_catchup($appname);
 
 $result =
-  $node_subscriber->safe_psql('postgres', "SELECT count(*), count(c), count(d = 999) FROM test_tab");
-is($result, qq(2|2|2), 'check extra columns contain local defaults');
+  $node_subscriber->safe_psql('postgres', "SELECT count(*), count(c), count(d = 999), count(e) FROM test_tab");
+is($result, qq(2|2|2|2), 'check extra columns contain local defaults after copy');
 
 # Change the local values of the extra columns on the subscriber,
 # update publisher, and check that subscriber retains the expected
@@ -67,5 +67,15 @@ $result =
   $node_subscriber->safe_psql('postgres', "SELECT count(*), count(extract(epoch from c) = 987654321), count(d = 999) FROM test_tab");
 is($result, qq(2|2|2), 'check extra columns contain locally changed data');
 
+# Another insert
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO test_tab VALUES (3, 'baz')");
+
+$node_publisher->wait_for_catchup($appname);
+
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*), count(c), count(d = 999), count(e) FROM test_tab");
+is($result, qq(3|3|3|3), 'check extra columns contain local defaults after apply');
+
 $node_subscriber->stop;
 $node_publisher->stop;