Fix application of identity values in some cases

Investigation of 2d2d06b7e27e3177d5bef0061801c75946871db3 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/backend/commands/copy.c

@@ -23,7 +23,6 @@
 #include "access/sysattr.h"
 #include "access/xact.h"
 #include "access/xlog.h"
-#include "catalog/dependency.h"
 #include "catalog/pg_type.h"
 #include "commands/copy.h"
 #include "commands/defrem.h"
@@ -2996,19 +2995,8 @@ BeginCopyFrom(ParseState *pstate,
 		{
 			/* attribute is NOT to be copied from input */
 			/* use default value if one exists */
-			Expr	   *defexpr;
-
-			if (att->attidentity)
-			{
-				NextValueExpr *nve = makeNode(NextValueExpr);
-
-				nve->seqid = getOwnedSequence(RelationGetRelid(cstate->rel),
-											  attnum);
-				nve->typeId = att->atttypid;
-				defexpr = (Expr *) nve;
-			}
-			else
-				defexpr = (Expr *) build_column_default(cstate->rel, attnum);
+			Expr	   *defexpr = (Expr *) build_column_default(cstate->rel,
+																attnum);
 
 			if (defexpr != NULL)
 			{

src/backend/commands/tablecmds.c

@@ -5486,7 +5486,21 @@ ATExecAddColumn(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	if (relkind != RELKIND_VIEW && relkind != RELKIND_COMPOSITE_TYPE
 		&& relkind != RELKIND_FOREIGN_TABLE && attribute.attnum > 0)
 	{
-		defval = (Expr *) build_column_default(rel, attribute.attnum);
+		/*
+		 * For an identity column, we can't use build_column_default(),
+		 * because the sequence ownership isn't set yet.  So do it manually.
+		 */
+		if (colDef->identity)
+		{
+			NextValueExpr *nve = makeNode(NextValueExpr);
+
+			nve->seqid = RangeVarGetRelid(colDef->identitySequence, NoLock, false);
+			nve->typeId = typeOid;
+
+			defval = (Expr *) nve;
+		}
+		else
+			defval = (Expr *) build_column_default(rel, attribute.attnum);
 
 		if (!defval && DomainHasConstraints(typeOid))
 		{

src/backend/nodes/copyfuncs.c

@@ -2819,6 +2819,7 @@ _copyColumnDef(const ColumnDef *from)
 	COPY_NODE_FIELD(raw_default);
 	COPY_NODE_FIELD(cooked_default);
 	COPY_SCALAR_FIELD(identity);
+	COPY_NODE_FIELD(identitySequence);
 	COPY_NODE_FIELD(collClause);
 	COPY_SCALAR_FIELD(collOid);
 	COPY_NODE_FIELD(constraints);

src/backend/nodes/equalfuncs.c

@@ -2564,6 +2564,7 @@ _equalColumnDef(const ColumnDef *a, const ColumnDef *b)
 	COMPARE_NODE_FIELD(raw_default);
 	COMPARE_NODE_FIELD(cooked_default);
 	COMPARE_SCALAR_FIELD(identity);
+	COMPARE_NODE_FIELD(identitySequence);
 	COMPARE_NODE_FIELD(collClause);
 	COMPARE_SCALAR_FIELD(collOid);
 	COMPARE_NODE_FIELD(constraints);

src/backend/nodes/outfuncs.c

@@ -2814,6 +2814,7 @@ _outColumnDef(StringInfo str, const ColumnDef *node)
 	WRITE_NODE_FIELD(raw_default);
 	WRITE_NODE_FIELD(cooked_default);
 	WRITE_CHAR_FIELD(identity);
+	WRITE_NODE_FIELD(identitySequence);
 	WRITE_NODE_FIELD(collClause);
 	WRITE_OID_FIELD(collOid);
 	WRITE_NODE_FIELD(constraints);

src/backend/parser/parse_utilcmd.c

@@ -472,6 +472,14 @@ generateSerialExtraStmts(CreateStmtContext *cxt, ColumnDef *column,
 
 	cxt->blist = lappend(cxt->blist, seqstmt);
 
+	/*
+	 * Store the identity sequence name that we decided on.  ALTER TABLE
+	 * ... ADD COLUMN ... IDENTITY needs this so that it can fill the new
+	 * column with values from the sequence, while the association of the
+	 * sequence with the table is not set until after the ALTER TABLE.
+	 */
+	column->identitySequence = seqstmt->sequence;
+
 	/*
 	 * Build an ALTER SEQUENCE ... OWNED BY command to mark the sequence as
 	 * owned by this column, and add it to the list of things to be done after

src/backend/rewrite/rewriteHandler.c

@@ -844,17 +844,7 @@ rewriteTargetListIU(List *targetList,
 		{
 			Node	   *new_expr;
 
-			if (att_tup->attidentity)
-			{
-				NextValueExpr *nve = makeNode(NextValueExpr);
-
-				nve->seqid = getOwnedSequence(RelationGetRelid(target_relation), attrno);
-				nve->typeId = att_tup->atttypid;
-
-				new_expr = (Node *) nve;
-			}
-			else
-				new_expr = build_column_default(target_relation, attrno);
+			new_expr = build_column_default(target_relation, attrno);
 
 			/*
 			 * If there is no default (ie, default is effectively NULL), we
@@ -1123,6 +1113,16 @@ build_column_default(Relation rel, int attrno)
 	Node	   *expr = NULL;
 	Oid			exprtype;
 
+	if (att_tup->attidentity)
+	{
+		NextValueExpr *nve = makeNode(NextValueExpr);
+
+		nve->seqid = getOwnedSequence(RelationGetRelid(rel), attrno);
+		nve->typeId = att_tup->atttypid;
+
+		return (Node *) nve;
+	}
+
 	/*
 	 * Scan to see if relation has a default for this column.
 	 */

src/include/nodes/parsenodes.h

@@ -647,6 +647,8 @@ typedef struct ColumnDef
 	Node	   *raw_default;	/* default value (untransformed parse tree) */
 	Node	   *cooked_default; /* default value (transformed expr tree) */
 	char		identity;		/* attidentity setting */
+	RangeVar   *identitySequence; /* to store identity sequence name for ALTER
+								   * TABLE ... ADD COLUMN */
 	CollateClause *collClause;	/* untransformed COLLATE spec, if any */
 	Oid			collOid;		/* collation OID (InvalidOid if not set) */
 	List	   *constraints;	/* other constraints on column */

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;