[OSM-dev] OSM Database schema

[Tom Hughes]

Because 99% of the time all that is needed is the current version
of the object.

Now you could probably do something clever with a flag to mark the
current version which was included in the index, or as a condition
on a partial index, so that you could efficiently find the current
versions but bear in mind this schema originated many years ago on
a different database engine with less capabilities.

Basically a lot of what you see is history rather than design.

Tom

On 09/01/2020 11:39, Lorenzo Stucchi wrote:
> Thanks to both, for the redaction I forgot to add them, I initially skipped and after I forgot to put them.
> 
> Thanks also Maarteen for the quick explanation of the parameters.
> 
> Can you quickly explain the reason for having double tables for the element, like nodes and current_nodes? It is also related to the change in the license?
> 
> Thanks,
> Lorenzo
> 
>> Il giorno 9 gen 2020, alle ore 12:27, Tom Hughes <tom at compton.nu> ha scritto:
>>
>> There are redactions as well, when data has had to be removed and hidden
>> from the history for copyright reasons or whatever. There is a list:
>>
>> https://www.openstreetmap.org/redactions
>>
>> Tom
>>
>> On 09/01/2020 11:17, Maarten Deen wrote:
>>> Redaction_id will have bearing on the redaction bot https://wiki.openstreetmap.org/wiki/OSMF_Redaction_Bot
>>> Background: when OSM changed to ODbl, all changes made by people who did not agree had to be redacted.
>>> visible in the changeset will be the same as for node/way/relation: you can delete an item, and when it is deleted, visible=0.
>>> Maarten
>>> On 2020-01-09 11:29, Lorenzo Stucchi wrote:
>>>> Dear all,
>>>>
>>>> After the discussion that I started about the database schema I tried
>>>> to create a wiki page that explains it, I started the page on my user
>>>> wiki-page [1]. I started with few tables, but some elements present in
>>>> the tables are not so clear to me.
>>>>
>>>> So If you wanna try to contribute to that page, since a description of
>>>> the database can be provided to everyone. I will continue to modify it
>>>> ,trying to understand all the tables.
>>>>
>>>> Thanks to everyone that will help, or just make a suggestion about it.
>>>>
>>>>
>>>> Best,
>>>> Lorenzo
>>>>
>>>> [1]
>>>> https://wiki.openstreetmap.org/wiki/User:LorenzoStucchi/Description_DatabaseSchema
>>>>
>>>>
>>>>> Il giorno 4 gen 2020, alle ore 23:01, Martin Koppenhoefer
>>>>> <dieterdreist at gmail.com> ha scritto:
>>>>>
>>>>> sent from a phone
>>>>>
>>>>>> On 4. Jan 2020, at 17:28, Jean Marie Falisse <fa003029 at skynet.be>
>>>>>> wrote:
>>>>>>
>>>>>> Is it still true that in the OSM database, areas are not
>>>>>> represented as such?
>>>>>
>>>>> areas can be represented as areas through multipolygon relations
>>>>> which are always areas or by help of an additional tag
>>>>> (area=yes/no), or through plausibility (tags and their combinations
>>>>> may imply an area or not). There isn’t a dedicated area object,
>>>>> maybe this is what you meant. Areas are represented with ways, and
>>>>> tags or relations are required to define the ways as areas.
>>>>>
>>>>>> That would mean, for instance, that a pedestrian zone, let’s say
>>>>>> a big square in a city, cannot be made to be crossed diagonally
>>>>>> when used in a route planner. Am I right?
>>>>>
>>>>> typically routing engines operate on graphs, i.e. they do not route
>>>>> diagonally across areas, but this isn’t related to the question
>>>>> whether there is a dedicated datatype for areas or not.
>>>>>
>>>>> Cheers Martin
>>>>> _______________________________________________
>>>>> dev mailing list
>>>>> dev at openstreetmap.org
>>>>> https://lists.openstreetmap.org/listinfo/dev
>>>> _______________________________________________
>>>> dev mailing list
>>>> dev at openstreetmap.org
>>>> https://lists.openstreetmap.org/listinfo/dev
>>> _______________________________________________
>>> dev mailing list
>>> dev at openstreetmap.org
>>> https://lists.openstreetmap.org/listinfo/dev
>>
>>
>> -- 
>> Tom Hughes (tom at compton.nu)
>> http://compton.nu/
> 


-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/