[OSM-talk] osm2pgsql diff application with filtered OSM data

[Frederik Ramm]

Hi,

On 08.11.2018 15:34, Nick Whitelegg wrote:
> My question is this; given that not everything in the diff will be in my
> database (as I filter out what I don't need during the import process),
> will osm2pgsql apply the diff successfully or will it complain that not
> all features in the diff are in my database?

It will apply the diff as far as possible, but it will also add a lot of
unwanted/unnecessary stuff from the diff to the database which you would
then have to filter out again.

There's also a danger that you will miss some things. For example,
consider a rural garage (shop=car_repair) mapped as a way with four
nodes; you filter that out because you're not interested. Half a year
later the shop closes, and a tourism=hostel opens instead. Assuming you
are interested in this kind of POI, the diff that you process contains
the way with the new tags, but not the nodes since these have not
changed. The hostel will not appear in your osm2pgsql database because
the geometry cannot be built due to lack of nodes.

One way to avoid this downloading the full files, filtering them, and
then generating a diff by comparing the filtered file to the last
filtered file, and importing *that* diff.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"