Re: COPY, lock release and MVCC

Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> writes:
> On Mon, 2020-05-11 at 15:43 -0400, Robert Haas wrote:
>> On Fri, May 8, 2020 at 4:58 AM Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at> wrote:
>>> I happened to notice that COPY TO releases the ACCESS SHARE lock
>>> on the table right when the command ends rather than holding it
>>> until the end of the transaction:

>> That seems inconsistent with what an INSERT statement would do, and thus bad.

> Well, should we fix the code or the documentation?

I'd agree with fixing the code. Early lock release is something we do on
system catalog accesses, and while it hasn't bitten us yet, I've been
kind of expecting that someday it will. We should not do it on SQL-driven
accesses to user tables.

Having said that, I'd vote for just changing it in HEAD, not
back-patching. It's not clear that there are consequences bad enough
to merit a back-patched behavior change.

regards, tom lane