Re: Adding REPACK [concurrently]

Mihail Nikalayeu <mihailnikalayeu@gmail.com> wrote:

> Antonin Houska <ah@cybertec.at>:
> > I think the problem is that HeapTupleSatisfiesSelf() uses
> > TransactionIdIsInProgress() instead of checking the snapshot:
>
> Yes, some issues might be possible for SnapshotSelf.
> Possible solution is to override TransactionIdIsCurrentTransactionId
> to true (like you did with nParallelCurrentXids but just return true).
> IIUC, in that case all checks are going to behave the same way as in v5 version.

I assume you mean v12-0005. Yes, that modifies
TransactionIdIsCurrentTransactionId(), so that the the transaction being
replayed recognizes if it (or its subtransaction) performed particular change
itself.

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.

But the primary issue is that in v12-0005,
TransactionIdIsCurrentTransactionId() gets the information on "current
transactions" from snapshots - see the calls of SetRepackCurrentXids() before
each scan. It's probably not what you want.

--
Antonin Houska
Web: https://www.cybertec-postgresql.com