Re: reindex concurrently and two toast indexes

On Thu, Mar 05, 2020 at 12:53:54PM +0900, Michael Paquier wrote:
> On Wed, Mar 04, 2020 at 09:21:45AM +0100, Julien Rouhaud wrote:
> > Thanks for the patch!  I started to look at it during the weekend, but
> > I got interrupted and unfortunately didn't had time to look at it
> > since.
>
> No problem, thanks for looking at it.  I have looked at it again this
> morning, and applied it.
>
> > The fix looks good to me.  I also tried multiple failure scenario and
> > it's unsurprisingly working just fine.  Should we add some regression
> > tests for that?  I guess most of it could be borrowed from the patch
> > to fix the toast index issue I sent last week.
>
> I have doubts when it comes to use a strategy based on
> pg_cancel_backend() and a match of application_name (see for example
> 5ad72ce but I cannot find the associated thread).  I think that we
> could design something more robust here and usable by all tests, with
> two things coming into my mind:
> - A new meta-command for isolation tests to be able to cancel a
> session with PQcancel().
> - Fault injection in the backend.
> For the case of this thread, the cancellation command would be a better
> match.

I agree that the approach wasn't quite robust.  I'll try to look at adding a
new command for isolationtester, but that's probably not something we want to
put in pg13?

Here's a v3 that takes address the various comments you previously noted, and
for which I also removed the regression tests.

Note that while looking at it, I noticed another bug in RIC:

# create table t1(id integer, val text); create index on t1(val);
CREATE TABLE

CREATE INDEX

# reindex table concurrently t1;
^CCancel request sent
ERROR:  57014: canceling statement due to user request
LOCATION:  ProcessInterrupts, postgres.c:3171

# select indexrelid::regclass, indrelid::regclass, indexrelid, indrelid from pg_index where not indisvalid;
             indexrelid              |        indrelid         | indexrelid | indrelid
-------------------------------------+-------------------------+------------+----------
 t1_val_idx_ccold                    | t1                      |      16401 |    16395
 pg_toast.pg_toast_16395_index_ccold | pg_toast.pg_toast_16395 |      16400 |    16398
(2 rows)


# reindex table concurrently t1;
WARNING:  0A000: cannot reindex invalid index "public.t1_val_idx_ccold" concurrently, skipping
LOCATION:  ReindexRelationConcurrently, indexcmds.c:2821
WARNING:  XX002: cannot reindex invalid index "pg_toast.pg_toast_16395_index_ccold" concurrently, skipping
LOCATION:  ReindexRelationConcurrently, indexcmds.c:2867
REINDEX

# reindex index concurrently t1_val_idx_ccold;
REINDEX

That case is also fixed in this patch.