On 11/9/2004 8:54 AM, Ed L. wrote:
> On Tuesday November 9 2004 5:58, cbbrowne at ca.afilias.info wrote:
>> > On Monday November 8 2004 8:59, Jan Wieck wrote:
>> >> On 11/8/2004 9:58 PM, Ed L. wrote:
>> >> > I just had a 1.0.5 initial "copy set" fail after 2 hours of data
>> >> > copying. This was not slony's fault; the slon process got clobbered.
>> >> > Unfortunately, it rolled back all 2 hours of progress.  I don't have
>> >> > a patch to offer for this, but it would be nice to be able to commit
>> >> > partially thru the copy set and pick up where it left off ...
>> >>
>> >> Right, it would be nice. But I failed to figure out how to do this
>> >> without relying on the masters MVCC features while at the same time
>> >> ensuring that restarting against a possibly all the time heavily
>> >> updated master would still lead to a consistent initial copy. I don't
>> >> expect a patch ... I would settle for an idea.
>> >
>> > I wonder if you could somehow take note of a progress checkpoint after
>> > some
>> > amount of time on the nearest "truncateTable(...); copy table" boundary
>> > after the amount of time elapses?  Maybe sl_table.tab_initialized =
>> > false until each table is committed on the slave, then
>> > sl_table.tab_initialized
>> >
>> > := 'true'?  Then, if lights go out, you pick up with slave listing of
>> >
>> > tables where sl_table.tab_initialized = false before moving on to
>> > events. Not sure that qualifies as a usable idea.
>>
>> Alas, no...  The problem is in determining which table updates since the
>> COPY SET started need to be applied to the subscriber.
>>
>> If everything is done as one transaction, the answer is simple:  All of
>> it.
>>
>> Elsewhere lies madness, or at least something similar to madness.
> 
> I see the madness, no way to bookmark progress on the master without getting 
> way into MVCC. 

And with that MVCC mess, make "sure" that no vacuum on that master 
accidentially removes old rows. These are not locked by any existing 
transaction any more, because the COPYing slon got clobbered ... but we 
would like them to hang in there longer anyway. It is madness, indeed.


Jan

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