Joining a heterogeneous cluster v5.6

A PGD 4.0 node can join an EDB Postgres Distributed cluster running 3.7.x at a specific minimum maintenance release (such as 3.7.6) or a mix of 3.7 and 4.0 nodes. This procedure is useful when you want to upgrade not just the PGD major version but also the underlying PostgreSQL major version. You can achieve this by joining a 3.7 node running on PostgreSQL 12 or 13 to an EDB Postgres Distributed cluster running 3.6.x on PostgreSQL 11. The new node can also run on the same PostgreSQL major release as all of the nodes in the existing cluster.

PGD ensures that the replication works correctly in all directions even when some nodes are running 3.6 on one PostgreSQL major release and other nodes are running 3.7 on another PostgreSQL major release. However, we recommend that you quickly bring the cluster into a homogenous state by parting the older nodes once enough new nodes join the cluster. Don't run any DDLs that might not be available on the older versions and vice versa.

A node joining with a different major PostgreSQL release can't use physical backup taken with bdr_init_physical, and the node must join using the logical join method. Using this method is necessary because the major PostgreSQL releases aren't on-disk compatible with each other.

When a 3.7 node joins the cluster using a 3.6 node as a source, certain configurations, such as conflict resolution, aren't copied from the source node. The node must be configured after it joins the cluster.