Andra/Dragan - 

I'm sorry if my original message wasn't clear, but you have misunderstood one part of it: I am not trying to match IDs from Wikidata into my own Wikibase. For purposes of my question, Wikidata doesn't even need to exist. (Though I love wikidata)

Wikibase is a database. Unfortunately it does not support inserting new items and properties with a primary key. Wikibase creates those IDs and tells you what it assigns as the primary key.

I would like to be able to create new items in a Wikibase while specifying what the primary key should be. I understand that Wikibase requires that item keys start with 'Q' and property keys start with 'P', I can live with that. But I want to be able to set the ID that follows the P and Q when I create an entity in my own Wikibase. 

Wikidata does not need to be able to support specifying an ID when an entity is created, which I assume is why Wikibase doesn't support it. I am trying to understand how hard would it be to add optional support into Wikibase to provide the ID at entity creation time, even though it will never be turned on for Wikidata. 

Longer-term I think it would be awesome if I could provide my own IRI to use in place of a P<ID> or Q<ID>, but I understand that that is a bigger conversation.


On Fri, Jan 29, 2021 at 4:30 AM Dragan Espenschied <> wrote:
Hi both,

I agree with Andra that trying to match exact IDs doesn't make sense.

But also Erik points out a real issue with migration: at the moment,
the only possibility to back up a Wikibase instance is a full MySQL
dump/restore, which for better or worse contains much more that just
Wikibase data, but also information on user accounts, installed
extensions, etc.

Overall, current Wikibase hosting services should offer the the option
of SQL dumps to be exported and ideally imported, otherwise I wouldn't
advise to commit any important data into one.

Erik, while your idea for extending the API would present a quick fix,
I believe in the long run Wikibase must learn to import RDF. The export
already works. As some suggestions for the Wikibase REST API looked
like just working on the RDBM level instead of linked data, I'm kind of
afraid of any idea that would be "easy to implement" on top of MySQL,
as it will entrench the idea that linked data items are just special
Wikipages and RDF is just a second thought, which is causing a lot of
issues. One of them is that you cannot define URLs for your properties
and items, exactly the problem you want to solve.


On Fr, Jan 29, 2021 at 10:23, Andra Waagmeester <> wrote:
> Hi Eric,
>       Whenever I create a new Wikibase, the first property (P1)  I
> create is "Wikidata mapping" with a value data type URL. And for each
> Item that reflects a concept that exists in Wikidata, I add the URL
> for that wikidata item to the related Wikibase item. Doing so the
> items are now connected.
> With quite some caveats it is possible to replicate the Q numbers
> from WIkidata in Wikibase, however, using a mapping property is IMHO
> a preferred and more stable solution. One of those caveats is that it
> is not 100% full proof. For example, if you make a copy of Wikidata
> (or a subset) on day one, both your Wikibase and Wikidata will have
> separate lives. If that is not the case why bother setting up a
> Wikibase not simply rely on wikidata. So if at some time later want
> to again sync with wikidata, you have suddenly Qids on your Wikibase
> (ie. items you created) that have the exact same Qid of a totally
> different Wikidata item. Meaning that in the long run, you will not
> be able to sustain the Wikidata Qid.
> When I want to query my personal wikibase for a Wikidata item that I
> replicated in my Wikibase, I use the following query:
> "SELECT * WHERE {?item wbt:P1 wd:Q42 ; wbt:Pxx
> ?some_extra_annotation_not_in_wikidata } ."
> Andra
> On Fri, Jan 29, 2021 at 4:10 AM Erik Paulson <>
> wrote:
>> Hello -
>> Sorry for the crosspost/repeat - I sent a version of this to the
>> wikidata mailing list, but it was right in the peak of the holidays.
>> This list is probably more appropriate for it and hopefully by now
>> the wikibase developers are back from their holidays and all caught
>> up on email/year end/new year tasks, and can help provide some
>> guidance.
>> The tl;dr version of this post: On a blank Wikibase instance, I want
>> to be able to do:
>> api.php?action=wbeditentity&new=item&id=Q42&data={"labels":{"en":{"language":"en","value":"Douglas
>> Adams"}}}
>> I do not want to do this on - I understand why it makes
>> no sense in that context. But I would like to be able to do this on
>> my own Wikibase instance.
>> Beyond the whimsical like ensuring Doug Adams gets to be Q42, the
>> main reason for this is data portability and identifier stability.
>> As more hosted Wikibase providers come online and start offering
>> services, I want to know that I have data portability if I need to
>> change to a different provider. Anyone who queries my Wikibase needs
>> to know the identifiers my Wikibase uses for instances and more
>> importantly for classes, and if I change providers, those
>> identifiers cannot change without breaking those queries.
>> I do not think that MySQL backups are a reliable way to be able to
>> transition between providers. I am not confident that all providers
>> will want to offer a service where they accept a MySQL backup to
>> load into their Wikibase backend, and there are additional
>> challenges moving between Wikibase versions. (Though some may - I
>> programmatically create the contents of my Wikibase so I don't care
>> about edit history, but if one were to care about that history and
>> other things like wikiusers I imagine the MySQL dumps would be the
>> preferred way to migrate?)
>> One possible solution is to simply create blank items in a new
>> Wikibase, from 1 to the maximum identifier used in my old wikibase,
>> and then repopulate each item with the claims from my old Wikibase
>> instance. Unfortunately this is not a reliable solution because
>> while Wikibase guarantees that item IDs will not be reused, it does
>> not guarantee that every ID in the sequence will be created, e.g. in
>> rare cases Wikibase may go from Q41 to Q43 and skip/never create Q42.
>> I don't mind that the identifier needs to be prefixed with a 'Q' or
>> a 'P' for a particular type, I just want to be able to set the same
>> identifier if I set up a new wikibase instance.
>> I think Wikibase is awesome, but it is an odd database that does not
>> allow you to set the keys for the data you are managing :)
>> In reading through the Wikibase Repo code, it seems like this
>> scenario was considered though perhaps isn't fully implemented (or
>> has been disabled?). The code in EntitySavingHelper.php looks like
>> there are/were ways to call it by providing an ID while still asking
>> for a new entity, though there is logic earlier in the ModifyEntity
>> code to look for and explicitly reject the case where the API asks
>> for 'new' and also provides an ID, so I'm not sure how this code
>> path would get called. There is also code to ask the entityStores if
>> they 'canCreateWithCustomId', but those all appear to just return
>> 'false'?
>> However, if that logic was skipped in the API handler and a bit of
>> code reworked in ModifyEntity and EntitySavingHelper, along with
>> ensuring that that the next available ID is kept up to date in the
>> wb_id_counters table to always be 1 beyond the maximum ID in use, it
>> looks like it might not be that hard to enable creating entities
>> with specific IDs?
>> So three questions:
>> Would the Wikibase development team ever be open to supporting
>> something like this, behind a flag like
>> $wgWBRepoSettings['allowUserProvidedIds'] that defaulted to false?
>> Are there more complicated implications from allowing a change like
>> this that would need to be considered? I understand why the
>> repo needs this codepath fast and can't allow users to
>> provide IDs for new entities anyway, but are there other reasons
>> this isn't supported beyond "Wikidata doesn't need it?"
>> Is this all moot with the eventual REST API? I see that there's a
>> PUT envisioned, could I use that to directly create an item or
>> property and give it an ID then, or does the ID have to already
>> exist to replace it?
>> I am happy to try to tackle creating a patch for this, but I'd like
>> to get some feedback if there's any big lurking issues that I should
>> know about before starting on the work - I'd rather not get deep
>> into it only to find out it will never work or never be accepted.
>> I'm also happy to shift this to phabricator if that's more
>> appropriate.
>> Thank you all for your work on Wikibase!
>> Thanks,
>> -Erik
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