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help / color / mirror / Atom feedFrom: Mihail Nikalayeu <[email protected]>
To: Amit Kapila <[email protected]>
Cc: Zhijie Hou (Fujitsu) <[email protected]>
Cc: Peter Geoghegan <[email protected]>
Cc: Hayato Kuroda (Fujitsu) <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: [email protected]
Subject: Re: [BUG?] check_exclusion_or_unique_constraint false negative
Date: Wed, 27 Aug 2025 10:53:57 +0200
Message-ID: <CADzfLwWiTiT_LSMfPi+_NAp21aeO5m=09K2VuiF2pB4PJ6Ee2A@mail.gmail.com> (raw)
In-Reply-To: <CAA4eK1+7bNcjF5gRnfACgLMq1VPKQdD8fR43Rd93wdMzLqCbdA@mail.gmail.com>
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Hello, Amit!
Amit Kapila <[email protected]>:
> Now, I
> would like to know the opinion of others who were involved in the
> initial commit, so added Peter E. to see what he thinks of the same.
Seems like you added another Peter in [0] - I added Peter Eisentraut :)
> > Hmm.... Yes - if the TID lands to the page left of the current
> > position, we’ll miss it as well.
> > A lock‑based solution (version in the v10) would require keeping all
> > pages with the same key under a read lock, which feels too expensive.
> Right.
I think it is possible to achieve the same guarantees and logic using
GetLatestSnapshot + HeapTupleSatisfiesDirty, but without the "tuple
not found" case - I'll try to experiment with it.
GetLatestSnapshot is called before tuple lock anyway.
> I think it is better to document this race somewhere in a logical
> replication document for now unless we have a consensus on a way to
> move forward.
Yes, it is an option, but what documentation is going to be strange:
* there is delete_missing type of conflict stats\logs, but be aware it
may be wrong (actually it delete_missing)
* the same for update_missing vs update_origin_differs
* the same for update_deleted vs update_origin_differs
* also DELETE or UPDATE from publisher may be missed in case of update
on subscriber even if update touches subscriber-only columns
It looks like "if something is updating on subscriber - no
guarantees". And the worst thing - it is the actual state.
[0]: https://www.postgresql.org/message-id/flat/CAA4eK1LZxzORgAoDhix9MWrOqYOsNZuZLW2sTfGsJFM99yRgrg%40mai...
Best regards,
MIkhail.
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Subject: Re: [BUG?] check_exclusion_or_unique_constraint false negative
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