[Tile-serving] [osm2pgsql] Bad multipolygon tags (#80)

[apmon]

Thank you for your effort of creating those test cases. However, I am starting to wonder, if this might be a "won't fix" bug and the recommendation is to simply tag the multi-polygon relation correctly rather than try and infer/transfer the tagging from the member ways.

There is just too much semantic knowledge of the tags necessary to get this transfer correct in all cases with simple algorithms. The relevant code (for the c transform) is https://github.com/openstreetmap/osm2pgsql/blob/master/tagtransform.c#L523 to line 603.
There are some tags like "fixme" or "import:xyz" that should be ignored altogether, some tags that should be copied to the relation, and some tags should determine if the ways should remain as independent lines in addition to the multi-polygon. But how do you decide which tag is which for the 1000s of different tags?

At the moment it takes the hints from the import.style to decide which ones are which, but there are clearly more complex combinations that are relevant in this decision.

Nevertheless, the algorithm can probably be improved by only copying tags from outer ways that are present on all outer ways, rather than tags that are present on at least one outer way.

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Reply to this email directly or view it on GitHub:
https://github.com/openstreetmap/osm2pgsql/issues/80#issuecomment-24789354
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