Does PostgreSQL support read replicas?
Read replica limitations with PostgreSQL Each PostgreSQL read replicas is read-only. You can’t make a writable read replica. You can’t create a read replica from another read replica. Thus, you can’t create cascading read replicas.
How does Postgres read replica work?
PostgreSQL streaming replication leverages the Write Ahead Log (WAL). The replication works by continuously shipping segments of the WAL from the primary to any connected replicas. Each replica then applies the WAL changes and makes them available for querying.
What is Pg_last_xact_replay_timestamp?
pg_last_xact_replay_timestamp() timestamp with time zone. Get time stamp of last transaction replayed during recovery. This is the time at which the commit or abort WAL record for that transaction was generated on the primary. If no transactions have been replayed during recovery, this function returns NULL.
What is logical replication?
Logical replication is a method of replicating data objects and their changes, based upon their replication identity (usually a primary key). The subscriber applies the data in the same order as the publisher so that transactional consistency is guaranteed for publications within a single subscription.
How to export a snapshot in PostgreSQL 9.4?
The function pg_export_snapshot saves the current snapshot and returns a text string identifying the snapshot. This string must be passed (outside the database) to clients that want to import the snapshot. The snapshot is available for import only until the end of the transaction that exported it.
How does physical replication work in PostgreSQL master replica?
Depending on data streaming: Physical replication (WAL files are copied across the network and then replayed on the replica) and Logical replication (streaming is used to send data over real time).
What is the return value of PG _ switch _ xlog?
The return value is the ending transaction log location + 1 within the just-completed transaction log file. If there has been no transaction log activity since the last transaction log switch, pg_switch_xlog does nothing and returns the start location of the transaction log file currently in use.
Can a logical slot be moved from replication to replication?
There’s no way to copy an exported snapshot from primary to replica in order to dump data from a replica that’s consistent with a replication slot’s exported snapshot on the primary. (Nor is there any way to create or move a logical slot to be exactly consistently with an existing exported snapshot).