User:Push-f/Wikidata:Limitations/WDQS
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 | This is an information page. It is not one of Wikidata's policies or guidelines, but rather intends to describe some aspect(s) of Wikidata's norms, customs, technicalities, or practices. It may reflect varying levels of consensus and vetting. |
This page attempts to document the biggest current limitations of the Wikidata query service.
Query timeouts
[edit]Queries cannot take longer than 60 seconds or they are aborted.
See also Query optimization.
See also phab:T179879 and phab:T187424.
Unawareness of the data model
[edit]The WDQS doesn't understand the semantics of instance of (P31) and subclass of (P279) so if you want to query all instances of a class you have to use wdt:P31/wdt:P279*.
The same counts for other transitive properties like part of (P361).
Unhelpful for semantically wrong queries
[edit]There are many mistakes you can make in SPARQL queries that will make the queries silently fail (e.g. by returning no results). The WDQS unfortunately doesn't recognize such errors like:
- accidentally specifying the wrong prefix:
?item wd:P31 wd:Q5will never return anything (notice that it'swd:P31instead ofwdt:P31), the WDQS will just silently return no results - accidentally using the wrong syntax:
?item wdt:P2699 'http://example.com/'will never return any results because URLs have to be wrapped in <...> instead of quotation marks.
Bugs
[edit]- Changing the datatype of a property isn't propagated to the WDQS phab:T325886