Re: Single transaction in the tablesync worker?

On 11 Feb 2021, at 10:42, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Thu, Feb 11, 2021 at 1:51 PM Petr Jelinek
> <petr(dot)jelinek(at)enterprisedb(dot)com> wrote:
>>
>> On 10 Feb 2021, at 06:32, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>>
>>> On Wed, Feb 10, 2021 at 7:41 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>>>>
>>>> On Tue, Feb 9, 2021 at 10:38 AM Peter Smith <smithpb2250(at)gmail(dot)com> wrote:
>>>>>
>>>>
>>>> PSA v2 of this WalRcvExceResult patch (it is same as v1 but includes
>>>> some PG doc updates).
>>>> This applies OK on top of v30 of the main patch.
>>>>
>>>
>>> Thanks, I have integrated these changes into the main patch and
>>> additionally made some changes to comments and docs. I have also fixed
>>> the function name inconsistency issue you reported and ran pgindent.
>>
>> One thing:
>>
>>> + else if (res->status == WALRCV_ERROR &&
>>> + missing_ok &&
>>> + res->sqlstate == ERRCODE_UNDEFINED_OBJECT)
>>> + {
>>> + /* WARNING. Error, but missing_ok = true. */
>>> + ereport(WARNING,
>>> (errmsg("could not drop the replication slot \"%s\" on publisher",
>>> slotname),
>>> errdetail("The error was: %s", res->err)));
>>
>> Hmm, why is this WARNING, we mostly call it with missing_ok = true when the slot is not expected to be there, so it does not seem correct to report it as warning?
>>
>
> WARNING is for the cases where we don't always expect slots to exist
> and we don't want to stop the operation due to it. For example, in
> DropSubscription, for some of the rel states like (SUBREL_STATE_INIT
> and SUBREL_STATE_DATASYNC), the slot won't exist. Similarly, say if we
> fail (due to network error) after removing some of the slots, next
> time, it will again try to drop already dropped slots and fail. For
> these reasons, we need to use WARNING. Similarly for tablesync workers
> when we are trying to initially drop the slot there is no certainty
> that it exists, so we can't throw ERROR and stop the operation there.
> There are other cases like when the table sync worker has finished
> syncing the table, there we will raise an ERROR if the slot doesn't
> exist. Does this make sense?

Well, I was thinking it could be NOTICE or LOG to be honest, WARNING seems unnecessarily scary for those usecases to me.

—
Petr