Chengxu Bian

@hmottestad Hey, let's only include the rest api in this PR. I will have some future work on HttpRepo and workbench to utilize this api.

Is it a good idea to have a `search:context`? cc @hmottestad @kenwenzel @JervenBolleman ```sparql ?subj search:matches [ search:query "search terms..."; search:property my:property; search:context my:context; -----> allow users to specify the...

The current issue is: Imagine we have 100 RDF triples across two contexts, all containing the same object literal `"obj"`. The data is distributed as follows: #### In `` (99...

We introduced the memory catalog #412 It will be great if there is a in-memory example in doc to do a quick demo to users.

@hmottestad @kenwenzel Hello, I am interested in this feature and would like to contribute. If RDF4J maintainers still want this rest API, I am happy to discuss api design with...

### Add POST Request `/repositories/{repository_id}/explain` **Request Body:** ```json { "query": "SELECT * WHERE {?S ?O ?P}", "level": "Timed" } ``` **Response:** ```json { "explain": ".........." } ``` **Core Logic:** ```java...

@kenwenzel Good idea. If I understand correctly, we will use the existing SPARQL execution endpoints. If `explain=mode` is passed, it does query explanation, otherwise, execute this query.

#5312 good for review

Let me further explore the materialize-nothing solution to see how fast it can be.

Ok. Counting 10M triples without context filter only took 685.2 μs Counting triples within a context requires scanning all entires. It took 274.2ms to scan 5000000 triples. ``` Total Size:...