Perfectly clear.
Thanks a lot Jan.


J?r?mie.
 

> -----Message d'origine-----
> De : Jan Wieck [mailto:JanWieck at Yahoo.com] 
> Envoy? : mardi 26 octobre 2004 18:56
> ? : J?r?mie LOPEZ
> Cc : Darcy Buskermolen; slony1-general at gborg.postgresql.org
> Objet : Re: [Slony1-general] does slony currently do support 
> sequences?
> 
> On 10/26/2004 12:02 PM, J?r?mie LOPEZ wrote:
> > Thanks Darcy,
> > 
> > but does this mean that if I execute a SETVAL or NEXTVAL for a 
> > sequence on the master, wait for the replication to be done and 
> > execute a CURRVAL for this sequence on the master and on a 
> slave, I should see the same value?
> > (because I don't obtain this result... :-S)
> 
> You will never be able to call currval() without a prior 
> nextval() in the same session. You probably mean "select 
> last_value from seq".
> 
> Sequences replicated by Slony do not follow exactly the same 
> semantics as tables. Each time a SYNC event is generated on 
> the origin of data, the current values of all sequences is 
> recorded. because of the difference in concurrency and 
> visibility of changes between tables and sequences, these 
> recorded values might include changes to the sequence that 
> are not yet visible (committed) and therefore the 
> corresponding table data changes will not yet get replicated 
> with that SYNC event. 
> Since sequences in PostgreSQL are not guaranteed to be gap 
> free and don't roll back, this is acceptable. The do get 
> correctly adjusted on switchover and they might be more 
> advanced due to lost transactions in the case of a failover. 
> So they follow exactly the PostgreSQL sequence semantics.
> 
> Calling nextval() or setval() on the origin alone will not 
> trigger any Slony replication activity by itself. To do so, 
> you would have to call
> nextval() on the sl_action_seq also.
> 
> 
> Jan
> 
> > 
> > 
> >> -----Message d'origine-----
> >> De : Darcy Buskermolen [mailto:darcy at wavefire.com] Envoy? 
> : mardi 26 
> >> octobre 2004 17:43 ? : slony1-general at gborg.postgresql.org
> >> Objet : Re: [Slony1-general] does slony currently do support 
> >> sequences?
> >> 
> >> On October 26, 2004 05:18 am, J?r?mie LOPEZ wrote:
> >> > Well, all is said in the subject, but I can clear the
> >> question by the
> >> > fact that when I first heard of slony, I was told it 
> didn't support 
> >> > sequences (i.e. the current value of a sequence isn't updated on 
> >> > slaves, so you have to update it manually before making a
> >> master from
> >> > a slave) ; now that I have tried slony (which is a real
> >> cool project
> >> > btw :)) and want to get deeper in its possibilities, I find some 
> >> > interesting slonik commands like SET ADD SEQUENCE.
> >> > So its seems that sequences should be supported (even if 
> there is a 
> >> > workaround - with MERGE SET - to use to add sequences to a 
> >> > already-subscribed set) ; but after having done some 
> tests, I can't 
> >> > succeed in replicating the current value of a sequence.
> >> >
> >> > So? Are the SET * SEQUENCE commands some kind of 'coming soon' 
> >> > commands? Or am I wrong somewhere?
> >> 
> >> Yes sequences are fully supported, and have been since the first 
> >> official release.
> >> 
> >> 
> >> >
> >> >
> >> > TIA,
> >> >
> >> > J?r?mie.
> >> 
> >> --
> >> Darcy Buskermolen
> >> Wavefire Technologies Corp.
> >> ph: 250.717.0200
> >> fx:  250.763.1759
> >> http://www.wavefire.com
> >> _______________________________________________
> >> Slony1-general mailing list
> >> Slony1-general at gborg.postgresql.org
> >> http://gborg.postgresql.org/mailman/listinfo/slony1-general
> >> 
> > 
> > 
> > 
> > 
> ----------------------------------------------------------------------
> > --
> > 
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> > Slony1-general at gborg.postgresql.org
> > http://gborg.postgresql.org/mailman/listinfo/slony1-general
> 
> 
> --
> #=============================================================
> =========#
> # It's easier to get forgiveness for being wrong than for 
> being right. #
> # Let's break this rule - forgive me.                         
>          #
> #================================================== 
> JanWieck at Yahoo.com #
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