[openstreetmap/openstreetmap-website] Increase may key and value max length (#2025)

Tobias Zwick notifications at github.com
Fri Oct 12 15:59:07 UTC 2018


Some OSM tags do not (always) fit into the 255-character-limit imposed by the OSM API. This is a feature request to either increase the limit or remove it altogether.

### Discussion

There is a [discussion in the tagging mailing list right now](https://lists.openstreetmap.org/pipermail/tagging/2018-October/039889.html) about how to deal with a very complicated opening hours which is too long to fit into one value.

Citing @simonpoole :
> We have a number of keys for which the values can easily exceed 255 chars besides opening_hours, lane destinations and conditional restrictions are good candidates. Not to mention changeset tags. With other words it is a general problem which should be tackled with a general solution.

So, we passed the point where value-lengths above 255 characters are unrealistic for structured data, data that is not prose.

### Solutions

In the above discussion, the general opinion seemed to be that the OSM API will not change (until the unicorny API 0.7) and thus we have to workaround this.

There have been some suggestions towards a general-purpose syntax splitting up the actual value in different keys, like `opening_hours`, `opening_hours#2`, ... I think this is a very bad solution, because it requires **each and every** application and library that works with OSM data to implement this kind of tag concatenation - for any key, not just `opening_hours`, because this kind of enumeration scheme is supposed to be a generic solution

In #1593, I read that the limitation to 255 characters is actually a legacy from back when the OSM database was running on MySQL. So, removing that limitation, or increasing it somewhat, seems to be the swiftest solution because a weird workaround is avoided and it doesn't require a change in applications that use OSM data.
The only change that should be done would be to remove/change the client-side checks for tag lengths (editors).

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