What does it mean to have a changeset open? (versus a closed one) What are the advantages of it?

I tried to search about this in the wiki with no success.

This question is marked "community wiki".

asked 19 Jan '14, 20:33

jgpacker's gravatar image

jgpacker
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What does it mean to have a changeset open?

It means that you can add new objects/actions to this changeset. It is the opposite of a closed changeset. Technically, changesets are "open" after their creation. Open changesets are (currently) automatically closed one hour after the last addition to them. You also can close a changeset manually (but that is not needed in many cases).

The approaches vary between the editor software: iD and JOSM (in the default settings) automatically close a changeset after uploading, whereas Potlatch 2 keeps a changeset open and stuffs the next upload into it, too.

What are the advantages of it?

You can add new objects/actions to this changeset by more uploads. If changesets would not have a "open" state you would need to upload all changes which should belong to a changeset in one go.

See also changeset in the wiki.

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answered 19 Jan '14, 22:02

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aseerel4c26 ♦
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edited 04 Dec '16, 00:10

Personally I think they could wait more time before automatically closing it, but maybe that's just me.

(19 Jan '14, 23:45) jgpacker

Think of a changeset as a way of grouping similar changes together. If there wasn't a concept of "leaving a changset open" the "changesets" would only be defined by the uploads to OSM that you make, which might be overly large (grouping together lots of edits in lots of different places) or overly small (making it difficult to see a series of changes as a whole).

It's especially useful to users of web-based editors such as Potlatch where the changes to be made are reflected in the browser state rather than a .osm file that can be uploaded later, and frequent saves are a way of avoiding data loss.

Of course, whichever editor they're using, mappers still need to think about using descriptive changeset comments, and ensuring that changesets aren't too geographically wide-ranging to enable other mappers to see what areas are actually being changed. For example, right now this is at the top of the history list for the map where I live, and I have no way of knowing without further analysis what changes are in there from the comment ("Diverses" is just "various" in French) or the bounding box (an area stretching from Western Canada to Western Germany).

(apologies to the author of that changeset BTW - I literally did pick the top of the history list, so it was an entirely random selection).

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answered 19 Jan '14, 21:48

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SomeoneElse ♦
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Changesets puts edits together and represent a transactional unit in OSM database(you can revert a whole changeset in the server side if there is a copyright infringement, vandalism and/or massive data corruption). Their comment tags are actually very meaningful if any reverts needed. You "finalize" the transaction by closing the changeset.

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answered 19 Jan '14, 20:44

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erkinalp
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edited 19 Jan '14, 20:50

I think I wasn't clear, I know what is a changeset, what I want to know is why is there an open versus a closed changeset. Why/How can I use an 'open' changeset? Is that like saving your work to continue later?

(19 Jan '14, 21:04) jgpacker
1

Suppose you are mapping a dense city. You would be adding large numbers of objects. The server has to create one by one. You can divide your editing into town or neighbourhood-sized changesets and ease the upload and DB change. If you leave your changeset open, you can return into that edit and make relevant changes more.

(19 Jan '14, 21:12) erkinalp
2

Ok, with all the answers, I think I got it now. For example, let's say I'm uploading various small changes from two distant neighborhoods, I can start uploading one changes from one of them as 'open'. If I see I forgot to upload together some change of this first neighborhood, I can simply add it to the already uploaded 'open' changeset.

Other case scenario: I added new objects, and uploaded them as a 'open' changeset. After the upload I noticed I could do some fine-tuning in some parts. I can upload this fine-tuning to the already uploaded 'open' changeset.

Thanks for the help!

(19 Jan '14, 22:10) jgpacker

Do not forget that there is a hour's long timeout.

(01 Mar '17, 19:03) erkinalp

This answer is actually wrong, a changeset is NOT a "transactional unit", a changeset is not more than a grouping of edits.

(01 Mar '17, 21:04) SimonPoole ♦

There is such a thing as a partial transaction, OSM changesets work exactly like that. They are applied immediately but reverted in full.

(02 Mar '17, 07:48) erkinalp
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question asked: 19 Jan '14, 20:33

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last updated: 02 Mar '17, 07:48

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