Hi Han,
Yes, it appears to be a bug. I can recreate it although I had to
increase the loop count to 5000 to see anything going wrong.
It looks like once the test is wrong, it is wrong for 10+ iterations
afterwards, becomes OK again, and maybe goes wrong again. Quite strange,
and no concurrency in sight.
If the test is changed to use a plain model with the materialised
inference model copied into it, it does not go wrong.
Recorded: JENA-2184
Andy
https://issues.apache.org/jira/browse/JENA-2184
On 11/10/2021 11:04, Kruiger, J.F. (Han) wrote:
Hi there,
We are running into an issue that seems like a bug in Jena 4.2.0.
A (reasonably) minimal example is in this test case:
https://github.com/barrynl/jena-example/blob/cf2da8e5c7cd9a0f415282486ec8472e53d0a9c4/src/main/java/nl/tno/ict/ds/cb/jena/JenaRepeatedQueryOnInfModelTest.java
What happens there is:
* An `InfModel` is created from a reasoner that is bound to some RDF
data.
* The triples from the `InfModel` are written to a file `before.ttl`,
for debugging.
* A SELECT query is fired on the model repeatedly.
* After this, the triples from the same model are written to
`after.ttl`, for debugging.
The expected behaviour is:
* Since nothing changes in the model, the results of the subsequent
SELECT queries should be identical.
* `before.ttl` and `after.ttl` should be identical.
However, both of those things do not happen in the actual behaviour.
What we see (tested on my Linux machine, and my colleague's Windows
machine) is the following:
* For the first ~100 query results, there are not matches found and
the empty binding set is returned. (This is correct!)
* After that, something mysterious happens and the query suddenly
gives a binding as a result. (This is incorrect!)
* In `before.ttl`, both instances in the triple data are (correctly)
classified as `ic:InformPurpose` and `ic:Purpose`, but in
`after.ttl`, one of the resources is not classified as `ic:Purpose`
anymore (even though the model hasn't changed; only SELECT queries
were fired).
Note that this behaviour does not occur when we use Jena 4.1.0.
Are we missing something, or is this indeed a bug?
Best,
Han Kruiger
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