[Pgpool-general] Order of Query Results

[Guillaume Lelarge]

Le 28/07/2010 17:16, Sean Brown a écrit :
> On Wednesday, July 28, 2010 10:56:27 am you wrote:
>> Le 28/07/2010 16:50, Sean Brown a écrit :
>>> Does PgPool have an issue with the order of results from a query being
>>> returned in a different order?
>>>
>>> With the ongoing issue of our cluster falling out, we just had one member
>>> fall out again and again, no error in PostgreSQLs log is recorded.
>>> PgPool reports the possible last query was:
>>> select * from carts where cart_id in (11835,11824,11819)
>>>
>>> Specifically the error in PgPools log is:
>>> read_kind_from_backend: 1 th kind D does not match with master or
>>> majority connection kind ^@
>>> 2010-07-28 10:21:23 ERROR: pid 28242: kind mismatch among backends.
>>> Possible last query was: "select * from carts where cart_id in
>>> (11835,11824,11819)" kind details are: 1[D]
>>>
>>> If I run that query on the remaining node and on the one that just fell
>>> out, I get the same 3 results, but the orders of the records are
>>> different.
>>
>> The query you show doesn't ask for a specific order (no "ORDER BY"
>> clause), so each backend can send the data in whatever order they "prefer".
> 
> That I understand, what I am wondering is if this will cause PgPool to believe 
> there is an error in the information returned from the backends, even if the 
> only difference is the difference in order?
> 
> If it does, I assume the best way to deal with it is add order by's to every 
> query passed to pgpool?
> 

That's actually really good questions, and I don't have an answer to
them. CC back the list to know if other people have an answer to give us.


-- 
Guillaume
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