Re: recovering from "found xmin ... from before relfrozenxid ..."

On Wed, Sep 16, 2020 at 9:14 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Ashutosh Sharma <ashu(dot)coek88(at)gmail(dot)com> writes:
> > On Wed, Sep 16, 2020 at 1:25 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> * Should any of the other tables in the test be converted to temp?
>
> > Are you trying to say that we can achieve the things being done in
> > test-case 1 and 2 by having a single temp table and we should aim for
> > it because it will make the test-case more efficient and easy to
> > maintain?
>
> Well, I'm just looking at the comment that says the reason for the
> begin/rollback structure is to keep autovacuum's hands off the table.
> In most if not all of the other places where we need that, the preferred
> method is to make the table temp or mark it with (autovacuum = off).
> While this way isn't wrong exactly, nor inefficient, it does seem
> a little restrictive. For instance, you can't easily test cases that
> involve intentional errors.
>
> Another point is that we have a few optimizations that apply to tables
> created in the current transaction. I'm not sure whether any of them
> would fire in this test case, but if they do (now or in the future)
> that might mean you aren't testing the usual scenario for use of
> pg_surgery, which is surely not going to be a new-in-transaction
> table. (That might be an argument for preferring autovacuum = off
> over a temp table, too.)
>

I agree with you on both the above points. I'll try to make the
necessary changes to address all your comments. Also, I'd prefer
creating a normal heap table with autovacuum = off over the temp table
for the reasons you mentioned in the second point.

--
With Regards,
Ashutosh Sharma
EnterpriseDB:http://www.enterprisedb.com