Re: row filtering for logical replication

On 11/23/18 8:14 PM, Petr Jelinek wrote:
> On 23/11/2018 19:29, Fabrízio de Royes Mello wrote:
>>
>> On Fri, Nov 23, 2018 at 4:13 PM Petr Jelinek
>> <petr.jelinek@2ndquadrant.com <mailto:petr.jelinek@2ndquadrant.com>> wrote:
>>>
>>>>
>>>> If carefully documented I see no problem with it... we already have an
>>>> analogous problem with functional indexes.
>>>
>>> The difference is that with functional indexes you can recreate the
>>> missing object and everything is okay again. With logical replication
>>> recreating the object will not help.
>>>
>>
>> In this case with logical replication you should rsync the object. That
>> is the price of misunderstanding / bad use of the new feature.
>>
>> As usual, there are no free beer ;-)
>>
> 
> Yeah but you have to resync whole subscription, not just single table
> (removing table from the publication will also not help), that's pretty
> severe punishment. What if you have triggers downstream that do
> calculations or logging which you can't recover by simply rebuilding
> replica? I think it's better to err on the side of no data loss.
> 

Yeah, having to resync everything because you accidentally dropped a
function is quite annoying. Of course, you should notice that while
testing the upgrade in a testing environment, but still ...

> We could also try to figure out a way to recover from this that does not
> require resync, ie perhaps we could somehow temporarily force evaluation
> of the expression to have current snapshot.
> 

That seems like huge a can of worms ...


cheers

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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