Re: fixing old_snapshot_threshold's time->xid mapping

On Tue, Apr 21, 2020 at 3:44 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>
> On Tue, Apr 21, 2020 at 2:05 PM Thomas Munro <thomas.munro@gmail.com> wrote:
> > As before, these two apply on top of Robert's patches (or at least his
> > 0001 and 0002).
>
> While trying to figure out if Robert's 0003 patch was correct, I added
> yet another patch to this stack to test it.  0006 does basic xid map
> maintenance that exercises the cases 0003 fixes, and I think it
> demonstrates that they now work correctly.

+1,  I think we should also add a way to test the case, where we
advance the timestamp by multiple slots.  I see that you have such
case
e.g
+# test adding minutes while the map is not full
+set_time('3000-01-01 02:01:00Z');
+is(summarize_mapping(), "2|02:00:00|02:01:00");
+set_time('3000-01-01 02:05:00Z');
+is(summarize_mapping(), "6|02:00:00|02:05:00");
+set_time('3000-01-01 02:19:00Z');
+is(summarize_mapping(), "20|02:00:00|02:19:00");

But, I think we should try to extend it to test that we have put the
new xid only in those slots where we suppose to and not in other
slots?.


--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com