Version

5.3.0-SNAPSHOT

What happened?

The cancel signal in QueryExecDataset is only placed into the context when a timeout is configured.

However, in the case of manual invocations to QueryExec.abort() the cancel signal is not placed into the context.
This prevents functions to check the flag and possibly abort prematurely.

A use case is the query which uses the GeoSPARQL property function, which creates a cross product between all geometries (inside the property function) and returns all overlapping ones. @LorenzBuehmann has been working on a revised version that respects the cancel flag, however he noted that the flag is only available when timeouts have been configured, making it impossible to cancel externally using QueryExec.abort();

PREFIX geo: <http://www.opengis.net/ont/geosparql#>
SELECT * WHERE {
  ?x geo:sfIntersects ?y
}

Update: This issue started out with the cancel signal not always placed into an query execution's context, which prevented handling cancellation inside of functions and property functions after a manual abort via QueryExec.abort(). However, while working on this issue, it turned out that it is reasonable to extend the scope of this issue to make it possible to abort update executions via updateExec.abort().

The reason is, that update executions reuse the query execution machinery, but the context configured for the the update request was not forwarded to the query execution. This would e.g. cause custom functions registered with the update execution's context to not be available during query execution. While working on resolving this issue, I revised the update execution machinery to properly set up the context with the cancel signal, configure remaining query timeouts and introduce an updateExec.abort() method.

On large datasets, using the query above as the core to materialize spatial intersections between all pairs of geometries may run indefinitely, and it is useful to protect e.g. a Fuseki server against accidental long running updates with a timeout.

PREFIX geo: <http://www.opengis.net/ont/geosparql#>
INSERT {
  ?x <urn:intersectsWith> ?y # Custom materialization
}
WHERE {
  ?x geo:sfIntersects ?y # GeoSPARQL property function
}

Relevant output and stacktrace

No response

Are you interested in making a pull request?

Yes