Re: logical decoding and replication of sequences, take 2

FWIW there's two questions related to the switch to XLOG_SMGR_CREATE.

1) Does smgr_decode() need to do the same block as sequence_decode()?

/* Skip the change if already processed (per the snapshot). */
if (transactional &&
!SnapBuildProcessChange(builder, xid, buf->origptr))
return;
else if (!transactional &&
(SnapBuildCurrentState(builder) != SNAPBUILD_CONSISTENT ||
SnapBuildXactNeedsSkip(builder, buf->origptr)))
return;

I don't think it does. Also, we don't have any transactional flag here.
Or rather, everything is transactional ...

2) Currently, the sequences hash table is in reorderbuffer, i.e. global.
I was thinking maybe we should have it in the transaction (because we
need to do cleanup at the end). It seem a bit inconvenient, because then
we'd need to either search htabs in all subxacts, or transfer the
entries to the top-level xact (otoh, we already do that with snapshots),
and cleanup on abort.

What do you think?

regards

--
Tomas Vondra
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