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Synchronous replication! Yay!Synchronous replication! Yay!Posted May 5, 2011 20:25 UTC (Thu) by Cyberax (✭ supporter ✭, #52523)In reply to: Synchronous replication! Yay! by intgr Parent article: New features in PostgreSQL 9.1
Ok, I'm confused.
What happens when I commit a transaction? I understand that by the time COMMIT completes, the data is replicated to all the slaves. Right?
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Synchronous replication! Yay! Posted May 6, 2011 7:30 UTC (Fri) by intgr (subscriber, #39733) [Link]
Yes, by the end of COMMIT, the WAL data from the transaction is replicated to the slaves, but changes from the WAL haven't been applied to slave databases yet -- so not visible to queries. Applying/recovering the WAL on slaves still takes place asynchronously.
In the event of a failover/promotion, PostgreSQL applies all outstanding WAL changes, so no data is lost.
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