Re: logical replication of truncate command with trigger causes Assert

Mark Dilger <mark(dot)dilger(at)enterprisedb(dot)com> writes:
> On master, when a statement level trigger is fired for a replicated truncate command, the following stack trace is generated:

Hmm.

> I believe the issue was introduced in commit 84f5c2908da which added EnsurePortalSnapshotExists. That's not going to work in the case of logical replication, because there isn't an ActivePortal nor a snapshot.

The right way to say that is "commit 84f5c2908da exposed the pre-existing
unsafe behavior of this code". It's not okay to run arbitrary user code
without holding a snapshot to protect TOAST dereference operations.

I suppose that either apply_dispatch or LogicalRepApplyLoop needs to
grow some more snapshot management logic, but I've not looked at that
code much, so I don't have an opinion on just where to add it.

There's a reasonable case to be made that running user code outside
a Portal is a just-plain-bad idea, so we should fix the logical
apply worker to make it create a suitable Portal. I speculated about
that in the commit message for 84f5c2908da, but I don't feel like
taking point on such work.

regards, tom lane