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help / color / mirror / Atom feedFrom: Mihail Nikalayeu <[email protected]>
To: Antonin Houska <[email protected]>
Cc: Alvaro Herrera <[email protected]>
Cc: Fujii Masao <[email protected]>
Cc: Robert Treat <[email protected]>
Cc: Pg Hackers <[email protected]>
Subject: Re: Adding REPACK [concurrently]
Date: Tue, 26 Aug 2025 11:02:01 +0200
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Antonin Houska <[email protected]>:
> Although it could work, I think it'd be confusing to consider the transactions
> being replayed as "current" from the point of view of the backend that
> executes REPACK CONCURRENTLY.
Just realized SnapshotDirty is the thing that fits into the role - it
respects not-yet committed transactions, giving enough information to
wait for them.
It is already used in a similar pattern in
check_exclusion_or_unique_constraint and RelationFindReplTupleByIndex.
So, it is easy to detect the case of the race you described previously
and retry + there is no sense to hack around
TransactionIdIsCurrentTransactionId.
BWT, btree + SnapshotDirty has issue [0], but it is a different story
and happens only with concurrent updates which are not present in the
current scope.
[0]: https://www.postgresql.org/message-id/flat/CADzfLwXGhH_qD6RGqPyEeKdmHgr-HpA-tASYdi5onP%2BRyP5TCw%40m...
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Subject: Re: Adding REPACK [concurrently]
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