[OSM-dev] database schema

[Matt Amos]

2009/3/31 Pierre-André Jacquod <pjacquod at alumni.ethz.ch>:
> After some mapping, I am starting to have a look at the programming side
> of OSM. Just a question about the Database.

awesome :-)

> If I understood what I read under SVN (
> http://svn.openstreetmap.org/sites/rails_port/db/migrate/  currently
> Revision 14372) and the wiki
> http://wiki.openstreetmap.org/wiki/Database_schema (despite out of date
> warning), this is true that the nodes will still keep the key/val tag
> within the node's table as text DB column, and will not have a separated
> table / entry for that? (I am speaking with API 0.6 release, despite DB
> is not strictly an API issue)
>
> Or a change has not been yet committed?

the API 0.6 code is on a different branch:
http://svn.openstreetmap.org/sites/rails_port_branches/api06/ and
keeps node tags separately in a node_tags table.

the api06 migrations is probably the best place to look for the
current 0.6 schema - unless someone has a current
development_structure.sql lying around?

> By the way, would it be possible to setup the internet page in order to
> see the date / time of file commit? As hint about the accuracy of the entry?

on the wiki, just go to the history tab. for the schema page it was
last updated 12:16, 17 January 2009.

> If yes, could someone give me a reason (except historic one?).
>
> I am currently analyzing some osm-file entry (currently Switzerland) and
> found some value that are huge and not making any sense (just erroneous
> / bogus text without meaning). A limitation to varchar (255 or some
> greater) would not be better ?

this limit is present (and correctly enforced) in API 0.6. in 0.5 we
didn't have such a restriction on node tags, but it was present on way
and relation tags, albeit sometimes incorrectly truncated.

cheers,

matt