Re: "page is not marked all-visible" warning in regression tests

On Thu, Jun 7, 2012 at 11:04 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On Thursday, June 07, 2012 04:27:32 PM Robert Haas wrote:
>> On Thu, Jun 7, 2012 at 9:41 AM, Andres Freund <andres(at)2ndquadrant(dot)com>
> wrote:
>> >> Proposed patch attached.  This adds some more comments in various
>> >> places, and implements your suggestion of retesting the visibility-map
>> >> bit when we detect a possible mismatch with the page-level bit.
>> >
>> > Thanks, will look at it in a bit.
> I wonder if
>                /* mark page all-visible, if appropriate */
>                if (all_visible && !PageIsAllVisible(page))
>                {
>                        PageSetAllVisible(page);
>                        MarkBufferDirty(buf);
>                        visibilitymap_set(onerel, blkno, InvalidXLogRecPtr, vmbuffer,
>                                                          visibility_cutoff_xid);
>                }
> shouldn't test
>                if (all_visible &&
>                    (!PageIsAllVisible(page) || !all_visible_according_to_vm)
> instead.

Hmm, I think you're right.

> Commentwise I am not totally content with the emphasis on memory ordering
> because some of the stuff is more locking than memory ordering. Except that I
> think its a pretty clear improvement. I can reformulate the places where I
> find that relevant but I have the feeling that wouldn't help the legibility.
> Its the big comment in vacuumlazy.c, the comment in nodeIndexonly.c and the
> one in the header of visibilitymap_test. Should be s/memory-
> ordering/concurrency/ except in nodeIndexonlyscan.c

Hmm, I see your point.

> The visibilitymap_clear/PageClearAllVisible in heap_multi_insert should be
> moved into the critical section, shouldn't it?

Yes, it should. I was thinking maybe we could go the other way and
have heap_insert do it before starting the critical section, but
that's no good: clearing the visibility map bit is part of the
critical data change, and we can't do it and then forget to WAL-log
it.

Updated patch attached.

--
Robert Haas
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