Not quite - the history tables have all versions including
the current version.
So when a change is made to a node the current_nodes table is
changed to reflect the new details and a new record is added to
nodes with a new version number and the same details.
Yes, that is denormalised, but all real world databases are to
some extent ;-)
Tom
On 09/01/2020 11:54, Lorenzo Stucchi wrote:
So the meaning is that the last version of a node is saved in a table called
node_current, instead, all the old version are saved into a node table that has
the number of the version?
So the node is created in the current_node table, when it is modified the raw
is moved into the nodes table and the current_nodes is updated with the new
change. It is correct?
Thanks for pointing out this,
Lorenzo
Il giorno 9 gen 2020, alle ore 12:45, Tom Hughes <t...@compton.nu> ha scritto:
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 <t...@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
<dieterdre...@gmail.com> ha scritto:
sent from a phone
On 4. Jan 2020, at 17:28, Jean Marie Falisse <fa003...@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
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