Re: Re: new patch of MERGE (merge_204) & a question about duplicated ctid

* Robert Haas (robertmhaas@gmail.com) wrote:
> Like Heikki, I'd rather have the feature without a workaround for the
> concurrency issues than no feature.

I'm still trying to figure out the problem with having the table-level
lock, unless we really think people will be doing concurrent MERGE's
where they won't overlap..?  I'm also a bit nervous about if the result
of concurrent MERGE's would actually be correct if we're not taking a
bigger lock than row-level (I assume we're taking row-level locks as it
goes through..).

In general, I also thought/expected to have some kind of UPSERT type
capability with our initial MERGE support, even if it requires a big
lock and won't operate concurrently, etc.

> But I have to admit that the
> discussion we've had thus far gives me very little confidence that
> this code is anywhere close to bug-free.  So I think we're going to
> end up punting it to 9.2 not so much because it's not concurrency-safe
> as because it doesn't work.

That's certainly a concern. :/
Stephen