missing outer polygon(s) when diff update deletes a multipolygon relation

[cquest]

When a multipolygon is deleted by diff updates, its polygon is correctly deleted from planet_osm_polygon, but if the outer member ways are still there in the DB, their polygons are not recreated and thus missing after the update because they were not created because of the multipolygon.

It looks like delete_rels query may set pending back true on members to workaround this, but I'm not familiar enough with osm2pgsql code to offer a patch.

[apmon]

Yes, this is a long standing bug in the diff import code. It has been reported as https://trac.openstreetmap.org/ticket/4525
There also exists a patch to fix it, but so far it has never been committed, as the impact of it wasn't clear or if there is a better way.

However, as no one has done such an assessment or come up with a better way in the last 10 month, I will likely just go ahead and commit it soon and we will just have to live with the consequences to performance it entails.

[cquest]

I doubt it will have a big consequences on performances. Deleting relations is not something that happens so much.

[apmon]

Well, I have now committed the patch, which I believe should fix this.

If anyone does notice a significant drop in performance (or other issues), please report.

[apmon]

On 08/29/2013 12:09 PM, cquest wrote:

We've deployed this patch on a test server (layers.openstreetmap.fr)
but my first tests show that it does not fix the issue... :(

Do you have an example of where it doesn't work? It did fix the examples
I was aware of and I included in the test suite.

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[cquest]

I posted my comment a bit too quickly... i was just too impatient. The patch seems ok, sorry.

I'm just wondering now how to recover the lost polygons...