Hi,
On 11/05/2011 06:58 PM, mar...@gmx.eu wrote:
Meanwhile I found out that this node simply did not appear in the daily diffs:
http://www.openstreetmap.org/browse/node/1470178889
It was crated at 2011-10-16T23:58Z by a large changeset along with 23.000 other
nodes.
Neither the 16/17 nor the 17/18 daily diff contain this node whereas the hourly
diff from October 17 01:00 does.
There are two types of diffs; "replication diffs" and normal diffs. A
replication diff contains everything that happened between two
timestamps, including multiple changes of the same object, whereas a
normal diff only contains the information required to get from state 1
to state 2.
Also, replication diffs are created in a relatively fail-safe process
with Osmosis whereas the normal diffs can miss changes in some cases
when a long-running database transaction that was created before 0:00
extends past the time when the diff is created. (There was a time when
we had only "normal" diffs, and it was near impossible to make sure the
minutely/hourly ones did not miss anything.)
For minutely and hourly diffs, we only offer replication diffs these
days. For daily diffs, we have the normal ones under
planet.openstreetmap.org/daily, as well as the replication diffs under
planet.openstreetmap.org/history.
The normal diff indeed lacks the node in question, but the daily
replication diff under history/2011/1016-1017.osc.gz has it.
So, if you want to use daily diffs but avoid the danger of missing
edits, use the replication diff.
Frankly I don't know why the normal daily diffs are still created at
all; if one really wanted to offer a reduced-traffic version of the
replication diffs then it would indeed make sense to simply deflate the
replication diff using Osmosis' --simplify-change task.
Bye
Frederik
--
Frederik Ramm ## eMail frede...@remote.org ## N49°00'09" E008°23'33"
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