Wikidata Query Service/Problematic queries

This page lists queries which have some problems running in Blazegraph. Usually that means that we think they should be running fine but for one reason or another they do not. Note that this should not include queries that time out for legitimate reasons - like trying to scan repeatedly through whole database in 30 seconds or missing data triples, etc.

Hard queries
These queries time out or take a lot of time despite the fact that they should be simple. Each query should be accompanied with explanation why we think it is taking more time than it should.

Optimizer failures
These queries work well with optimizer disabled but not by default.