Fix the initial sync tables with no columns.

The copy command formed for initial sync was using parenthesis for tables
with no columns leading to syntax error. This patch avoids adding
parenthesis for such tables.

Reported-by: Justin G
Author: Vignesh C
Reviewed-by: Peter Smith, Amit Kapila
Backpatch-through: 15
Discussion: http://postgr.es/m/18203-df37fe354b626670@postgresql.org

Author: Amit Kapila

src/backend/replication/logical/tablesync.c

@@ -1124,22 +1124,30 @@ copy_table(Relation rel)
 	/* Regular table with no row filter */
 	if (lrel.relkind == RELKIND_RELATION && qual == NIL)
 	{
-		appendStringInfo(&cmd, "COPY %s (",
+		appendStringInfo(&cmd, "COPY %s",
 						 quote_qualified_identifier(lrel.nspname, lrel.relname));
 
-		/*
-		 * XXX Do we need to list the columns in all cases? Maybe we're
-		 * replicating all columns?
-		 */
-		for (int i = 0; i < lrel.natts; i++)
+		/* If the table has columns, then specify the columns */
+		if (lrel.natts)
 		{
-			if (i > 0)
-				appendStringInfoString(&cmd, ", ");
+			appendStringInfoString(&cmd, " (");
 
-			appendStringInfoString(&cmd, quote_identifier(lrel.attnames[i]));
+			/*
+			 * XXX Do we need to list the columns in all cases? Maybe we're
+			 * replicating all columns?
+			 */
+			for (int i = 0; i < lrel.natts; i++)
+			{
+				if (i > 0)
+					appendStringInfoString(&cmd, ", ");
+
+				appendStringInfoString(&cmd, quote_identifier(lrel.attnames[i]));
+			}
+
+			appendStringInfoString(&cmd, ")");
 		}
 
-		appendStringInfoString(&cmd, ") TO STDOUT");
+		appendStringInfoString(&cmd, " TO STDOUT");
 	}
 	else
 	{

src/test/subscription/t/001_rep_changes.pl

@@ -57,6 +57,11 @@
 	"CREATE INDEX idx_no_replidentity_index ON tab_no_replidentity_index(c1)"
 );
 
+# Replicate the changes without columns
+$node_publisher->safe_psql('postgres', "CREATE TABLE tab_no_col()");
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab_no_col default VALUES");
+
 # Setup structure on subscriber
 $node_subscriber->safe_psql('postgres', "CREATE TABLE tab_notrep (a int)");
 $node_subscriber->safe_psql('postgres', "CREATE TABLE tab_ins (a int)");
@@ -87,13 +92,16 @@
 	"CREATE INDEX idx_no_replidentity_index ON tab_no_replidentity_index(c1)"
 );
 
+# replication of the table without columns
+$node_subscriber->safe_psql('postgres', "CREATE TABLE tab_no_col()");
+
 # Setup logical replication
 my $publisher_connstr = $node_publisher->connstr . ' dbname=postgres';
 $node_publisher->safe_psql('postgres', "CREATE PUBLICATION tap_pub");
 $node_publisher->safe_psql('postgres',
 	"CREATE PUBLICATION tap_pub_ins_only WITH (publish = insert)");
 $node_publisher->safe_psql('postgres',
-	"ALTER PUBLICATION tap_pub ADD TABLE tab_rep, tab_full, tab_full2, tab_mixed, tab_include, tab_nothing, tab_full_pk, tab_no_replidentity_index"
+	"ALTER PUBLICATION tap_pub ADD TABLE tab_rep, tab_full, tab_full2, tab_mixed, tab_include, tab_nothing, tab_full_pk, tab_no_replidentity_index, tab_no_col"
 );
 $node_publisher->safe_psql('postgres',
 	"ALTER PUBLICATION tap_pub_ins_only ADD TABLE tab_ins");
@@ -141,6 +149,9 @@
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab_no_replidentity_index VALUES(1)");
 
+$node_publisher->safe_psql('postgres',
+	"INSERT INTO tab_no_col default VALUES");
+
 $node_publisher->wait_for_catchup('tap_sub');
 
 $result = $node_subscriber->safe_psql('postgres',
@@ -169,6 +180,10 @@
 	1,
 	"value replicated to subscriber without replica identity index");
 
+$result =
+  $node_subscriber->safe_psql('postgres', "SELECT count(*) FROM tab_no_col");
+is($result, qq(2), 'check replicated changes for table having no columns');
+
 # insert some duplicate rows
 $node_publisher->safe_psql('postgres',
 	"INSERT INTO tab_full SELECT generate_series(1,10)");