Allow primary node data modification with ALTER NODE

When trying to use ALTER NODE on a primary node, node manager was complaining
about the fact that there cannot be two primary nodes even if the data altered
was something else like host IP or port number.
The origin of the error was the error handling of primary node inside node
manager. For a newly-created node, it is checked with this new node is primary
and an error is returned if there is already a node defined. For an altered
node, it is checked if a node different than the one altered is primary and
if yes an error is returned. This check was originally moved inside
check_node_options but this was a bad bet as it decentralized the primary
node error check which is really different for new and altered nodes.

1 files changed, 25 insertions, 6 deletions

diff --git a/src/backend/pgxc/nodemgr/nodemgr.c b/src/backend/pgxc/nodemgr/nodemgr.c
index 1d1b5fb1a1..ee5ef63efb 100644
--- a/src/backend/pgxc/nodemgr/nodemgr.c
+++ b/src/backend/pgxc/nodemgr/nodemgr.c
@@ -184,18 +184,14 @@ check_node_options(const char *node_name, List *options, char **node_host,
 		}
 	}
 
-	/* Checks on primary and preferred nodes */
+	/* A primary node has to be a Datanode */
 	if (*is_primary && *node_type != PGXC_NODE_DATANODE)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
 				 errmsg("PGXC node %s: cannot be a primary node, it has to be a Datanode",
 						node_name)));
-	if (*is_primary && OidIsValid(primary_data_node))
-		ereport(ERROR,
-				(errcode(ERRCODE_SYNTAX_ERROR),
-				 errmsg("PGXC node %s: two nodes cannot be primary",
-						node_name)));
 
+	/* A preferred node has to be a Datanode */
 	if (*is_preferred && *node_type != PGXC_NODE_DATANODE)
 		ereport(ERROR,
 				(errcode(ERRCODE_SYNTAX_ERROR),
@@ -524,6 +520,16 @@ PgxcNodeCreate(CreateNodeStmt *stmt)
 	node_id = generate_node_id(node_name);
 
 	/*
+	 * Check that this node is not created as a primary if one already
+	 * exists.
+	 */
+	if (is_primary && OidIsValid(primary_data_node))
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("PGXC node %s: two nodes cannot be primary",
+						node_name)));
+
+	/*
 	 * Then assign default values if necessary
 	 * First for port.
 	 */
@@ -636,6 +642,19 @@ PgxcNodeAlter(AlterNodeStmt *stmt)
 				&node_port, &node_type,
 				&is_primary, &is_preferred);
 
+	/*
+	 * Two nodes cannot be primary at the same time. If the primary
+	 * node is this node itself, well there is no point in having an
+	 * error.
+	 */
+	if (is_primary &&
+		OidIsValid(primary_data_node) &&
+		node_id != primary_data_node)
+		ereport(ERROR,
+				(errcode(ERRCODE_SYNTAX_ERROR),
+				 errmsg("PGXC node %s: two nodes cannot be primary",
+						node_name)));
+
 	/* Check type dependency */
 	if (node_type_old == PGXC_NODE_COORDINATOR &&
 		node_type == PGXC_NODE_DATANODE)