Re: Allow ERROR from heap_prepare_freeze_tuple to be downgraded to WARNING

On Tue, Jul 21, 2020 at 9:21 AM Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> In the previous version, the feature was enabled for cluster/vacuum
> full command as well. in the attached patch I have enabled it only
> if we are running vacuum command. It will not be enabled during a
> table rewrite. If we think that it should be enabled for the 'vacuum
> full' then we might need to pass a flag from the cluster_rel, all the
> way down to the heap_freeze_tuple.

I think this is a somewhat clunky way of accomplishing this. The
caller passes down a flag to heap_prepare_freeze_tuple() which decides
whether or not an error is forced, and then that function and
FreezeMultiXactId use vacuum_damage_elevel() to combine the results of
that flag with the value of the vacuum_tolerate_damage GUC. But that
means that a decision that could be made in one place is instead made
in many places. If we just had heap_freeze_tuple() and
FreezeMultiXactId() take an argument int vacuum_damage_elevel, then
heap_freeze_tuple() could pass ERROR and lazy_scan_heap() could
arrange to pass WARNING or ERROR based on the value of
vacuum_tolerate_damage. I think that would likely end up cleaner. What
do you think?

I also suggest renaming is_corrupted_xid to found_corruption. With the
current name, it's not very clear which XID we're saying is corrupted;
in fact, the problem might be a MultiXactId rather than an XID, and
the real issue might be with the table's pg_class entry or something.

The new arguments to heap_prepare_freeze_tuple() need to be documented
in its header comment.

--
Robert Haas
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