Darcy Buskermolen wrote:
> On Wednesday 12 July 2006 10:01, Rod Taylor wrote:
>   
>> On Wed, 2006-07-12 at 12:43 -0400, Jan Wieck wrote:
>>     
>>> On 7/11/2006 12:43 PM, Christopher Browne wrote:
>>>       
>>>> I have set up tarballs for a first release candidate; Jan should be
>>>> uploading those soon, and I'll see about updating the web site when
>>>> they are uploaded...
>>>>         
>>> I have run them through a compile and a few tests and uploaded them to
>>> the usual location at
>>>
>>> http://developer.postgresql.org/~wieck/slony1/download/
>>>
>>> One thing I wanted to discuss is related to a recent discussion on the
>>> hackers mailing list with respect to possible btree corruption due to
>>> xxid not being suitable. With a single origin setup, there is not
>>>       
>> How about one partial index per node?
>>
>> CREATE INDEX node5_xid_idx ON sl_log_1(log_xid) WHERE log_origin = 5;
>>
>> This should give the performance benefits and prevent index rollover
>> problems.
>>
>> Since you rotate sl_log_N structures, it should be possible to slip in
>> the index creation or destruction when you truncate the sl_log_N
>> structure.
>>     
>
> This sounds like a valid solution to me,  Anybody else have any thoughts on 
> this ?
>   
It sure sounds like an interesting answer.

There would presumably be two times when you could safely create the
indexes without risk of slowing things up...

1.  When you do STORE NODE, it is known that sl_log_* will be empty on
that node.

2.  At truncate time, it is known that sl_log_* will be empty.

3.  When other nodes receive STORE_NODE events, then if there *isn't* a
log switch under way, the unused log is "fodder for modification."

4.  When other nodes receive STORE_NODE events, then if there *is* a log
switch under way, then one of the logs will shortly get modified.

5.  If STORE_NODE initiates a request for a log switch, that would lead
to adding in a missing index...

Open question:  Does partitioning the indices truly address the btree
corruption problem?  That feels like a question for Jan/Tom...