Christopher Browne wrote:
> Cyril SCETBON wrote:
>>
>>
>> Jan Wieck wrote:
>>> On 9/10/2007 10:07 AM, Cyril SCETBON wrote:
>>>> Hi,
>>>>
>>>> We're hitting 400 requests per second and noticed that sl_log_? are 
>>>> growing a lot. This is also due to the fact that our tables have a 
>>>> lot of columns (more that 100). We noticed that slony stores each 
>>>> column and its value for each request in sl_log_x. Would it not be 
>>>> more optimized to store just the user request ? Actually, a user is 
>>>> just updating a few column, or inserting a tuple by giving some 
>>>> attributes but not all, however as slony stores every column with 
>>>> its value it sl_log_x, these tables are growing very fast :-(
>>>
>>> Slony only logs columns where the value actually has changed. Please 
>>> explain in detail how you propose that the log table would contain 
>>> which columns have changed without naming them.
>> when I execute this command on the master :
>>
>> insert into t1(ise) values('cyril100001');
>>
>> I can see in sl_log_1 :
>>
>> psql>select log_cmddata from sl_log_1;
>> (ise,id,id2) values ('cyril100001','24161',NULL)
>>
>> dbtest=# \d t1;
>>                                Table "public.t1"
>> Column |         Type          |                    
>> Modifiers                   
>> --------+-----------------------+------------------------------------------------- 
>>
>> ise    | character varying(54) | not null
>> id     | integer               | not null default 
>> nextval('t1_id_seq'::regclass)
>> id2    | integer               |
>> Indexes:
>>    "t1_pkey" PRIMARY KEY, btree (ise)
>> Triggers:
>>    "_CLUSTER1_logtrigger_1" AFTER INSERT OR DELETE OR UPDATE ON t1 
>> FOR EACH ROW EXECUTE PROCEDURE "_CLUSTER1".logtrigger('_CLUSTER1', 
>> '1', 'kvv')
>>
>> I agree for id which is an auto_increment but not for id2 :-(
>>
>> In another plateform my table has more than  100 columns as said 
>> earlier and that's really matter :-(
> Jan's request seems to remain perfectly good...
>
> "Please explain in detail how you propose that the log table would 
> contain which columns have changed without naming them."
>
> It is *not* obvious how to avoid naming all of the columns.  It is not 
> safe to simply assume "that column was null so we may omit it" - 
> different nodes may be configured differently, and it may well be 
> important to actually have that NULL value.
I was just thinking of using the same way as other statement based 
replication way like does mysql, that is to say just log the request 
that user did. However, I forgot that slony uses triggers to log 
requests :-( Maybe finding a way to know which current request is done 
on the table for which the trigger has been called would be possible ?
>
>
>

-- 
Cyril SCETBON - Ingénieur bases de données
AUSY pour France Télécom - SCR/HDI/DOP/HEBEX

Tél : +33 (0)4 97 12 87 60
Jabber : cscetbon at jabber.org
France Telecom - Orange
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Bâtiment Marco Polo C2 
06250 Mougins
France

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