r/PostgreSQL • u/darkcoderrises • 13d ago
Feature Read your writes: WAIT FOR in PostgreSQL 19
https://clickhouse.com/blog/postgresql-19-wait-for-read-your-writes•
u/znpy 13d ago
Super cool!
How does it work with multiple replicas? Can I request a LSN to be acknowledged by like a majority of the replicas, or does it just need one replica to acknowledge that, or does it need all the replicas to acknowledge that ?
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u/rThoro 12d ago
it's actually for running a read query on the replica
so, assume your app only writes and never reads from primary, and all your reads go through the replica - if synchronous commit is off - you'll sometimes not be able to read you just written row - this let's you wait on the replica until the row is available
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u/znpy 11d ago
it's actually for running a read query on the replica
oh, i think i got it wrong then. i re-read the article, please help me check if i understood this correctly:
so basically my application does its usual write agains the primary node, but now i also ask the for the primary node LSN.
What changes is that now from SQL i can wait for the replica to catch up to (at least) the LSN i got earlier.
So basically i can manage the consistency guarantees from client side.
Is my understanding correct ?
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12d ago edited 12d ago
[removed] — view removed comment
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u/rThoro 12d ago
as explained here: https://www.reddit.com/r/PostgreSQL/s/j2mPkZOa4v
it's not about enforcing durability
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u/Inkbot_dev 6d ago
I've been waiting for this feature since it was first discussed on the mailing list well over a decade ago. So freaking happy it's finally in.
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u/forurspam 13d ago
It’s gonna be legendary