[OSM-dev] minute diff - max delay

[Tom Hughes]

On 14/08/10 00:19, Grant Slater wrote:
> On 14 August 2010 00:10, Brett Henderson<brett at bretth.com>  wrote:
>>
>> Is anybody aware of anything that happened on that day *other* than the
>> database upgrade?  Any new imports, etc.
>>
>
> The database was fully re-imported (planned and triple backed up) and
> the transaction IDs were reset due to this.
> zere was able to set the transaction id used by osmosis diff export
> because I believe you were not around or weren't available at the
> time.
>
> Also: Postgresql 8.3 ->  8.4. RAID10 on 10 disk to RAID 10 on 16 disks.
> RAID stripe size changed from 256KB to 64KB.

There's not really any great mystery here, we know it was the upgrade to 
postgres 8.4 (or just as likely the reimport of the db) that triggered it.

We just need to get to the bottom of what is making some of the queries 
run slowly, but it's not a very easy thing to do.

My assumption was that it was choosing a bad execution plan as the way 
our schema works tends to confuse Postgres's statistics, but the plan I 
looked at didn't show any sign of that.

Equally it doesn't seem to be a lock contention issue.

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/