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Posted to issues@jena.apache.org by "sszuev (via GitHub)" <gi...@apache.org> on 2024/01/15 09:17:31 UTC
[I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
sszuev opened a new issue, #2195:
URL: https://github.com/apache/jena/issues/2195
### Version
5.0.0-SNAPSHOT
### What happened?
The following code works fine in version 4.10.0, but throws an exception in version 5.0.0-SNAPSHOT:
```java
Model m = ModelFactory.createModelForGraph(new GraphTxn());
Node x = m.createResource("X", OWL.Class).asNode();
Graph g = m.getGraph();
ExtendedIterator<Triple> it = g.find(Triple.create(x, Node.ANY, Node.ANY));
it.toList();
g.add(Triple.create(NodeFactory.createURI("42"), Node.ANY, Node.ANY));
```
see also https://github.com/apache/jena/issues/1961
### Relevant output and stacktrace
```shell
org.apache.jena.sparql.JenaTransactionException: Tried to write inside a READ transaction!
at org.apache.jena.sparql.core.mem.DatasetGraphInMemory.mutate(DatasetGraphInMemory.java:378)
at org.apache.jena.sparql.core.mem.DatasetGraphInMemory.addToDftGraph(DatasetGraphInMemory.java:413)
at org.apache.jena.sparql.core.DatasetGraphTriplesQuads.add(DatasetGraphTriplesQuads.java:47)
at org.apache.jena.sparql.core.GraphView.performAdd(GraphView.java:147)
at org.apache.jena.graph.impl.GraphBase.add(GraphBase.java:158)
at org.apache.jena.sparql.graph.GraphWrapper.add(GraphWrapper.java:40)
at com.gitlab.sszuev.playjena.GraphTxnTest.test(GraphTxnTest.java:30)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
```
```
### Are you interested in making a pull request?
None
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "sszuev (via GitHub)" <gi...@apache.org>.
sszuev commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1891934937
and for a general understanding:
I see also `JenaTransactionException: Tried to write inside a READ transaction!`, or error about illegal nested transactions
so, in concurrent environment, it won't work? or error is expected to appear only in single thread environment (when our code calls read inside write or the opposite)?
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "afs (via GitHub)" <gi...@apache.org>.
afs closed issue #2195: [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException
URL: https://github.com/apache/jena/issues/2195
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "rvesse (via GitHub)" <gi...@apache.org>.
rvesse commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1891786883
`GraphTxn` is intended to provide auto-commit style semantics for `Graph`'s. However there was a bug in the `GraphTxn` implementation in the 4.10.0 release (#2086) where it incorrectly determined the current transaction state and wasn't always creating a transaction when necessary (and conversely would try to incorrectly create a transaction when unnecessary)
So the behaviour you are seeing with 5.0.0-SNAPSHOT is the correct expected behaviour
Creating the iterator starts a read transaction that isn't committed until you explicitly `close()` the iterator. Trying to do a `g.add()` tries to start a write transaction but it can't because the read transaction is still in progress.
If you plan to use `GraphTxn` seriously then you should explicitly manage the transactions to get the transaction boundaries appropriate to your application.
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "afs (via GitHub)" <gi...@apache.org>.
afs commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892822692
See also #2086, which backports a Jena5 fix to the Jena4 branch.
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "sszuev (via GitHub)" <gi...@apache.org>.
sszuev commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1891818752
this test works without exception in early releases, e.g. 4.7.0
perhaps it was always working incorrectly? If so, it would be surprise for end-users.
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "afs (via GitHub)" <gi...@apache.org>.
afs commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1902759437
There isn't anything remaining here outside of #2197 that I can see.
Please reopen if anything has been missed.
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "afs (via GitHub)" <gi...@apache.org>.
afs commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892798174
> I guess the returned iterator isn't aware that toList() effectively consumes it so it isn't close()'d
Looks that way. The code isn't seeing hasNext: true -> false nor is `hasNext` being called.
`GraphTxn.toList` uses `ExtendedIterator.forEachRemaining` which in `WrappedIterator` call the wrapped class and so bypasses `hasNext`.
For clarity - there is now a specific issue for this: https://github.com/apache/jena/issues/2197
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "sszuev (via GitHub)" <gi...@apache.org>.
sszuev commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1891974098
> `GraphTxn` is intended to provide auto-commit style semantics for `Graph`'s. However there was a bug in the `GraphTxn` implementation in the 4.10.0 release (#2086) where it incorrectly determined the current transaction state and wasn't always creating a transaction when necessary (and conversely would try to incorrectly create a transaction when unnecessary)
>
> So the behaviour you are seeing with 5.0.0-SNAPSHOT is the correct expected behaviour
>
> Creating the iterator starts a read transaction that isn't committed until you explicitly `close()` the iterator. Trying to do a `g.add()` tries to start a write transaction but it can't because the read transaction is still in progress.
>
> If you plan to use `GraphTxn` seriously then you should explicitly manage the transactions to get the transaction boundaries appropriate to your application.
additional note about the original issue. the following test also works in < 5.0.0-SNAPSHOT.
So, the easiest fix to add `close` in terminal operations (such as `toList`) won't help.
```
Node x = NodeFactory.createURI("X");
Node q = NodeFactory.createURI("Q");
GraphTxn g = new GraphTxn();
g.add(Triple.create(x, q, q));
ExtendedIterator<Triple> it = g.find(Triple.create(x, Node.ANY, Node.ANY));
it.next();
g.add(Triple.create(q, q, x));
```
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "sszuev (via GitHub)" <gi...@apache.org>.
sszuev commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892410709
One more exception. This time "Transactions cannot be nested!"
```
GraphTxn g = new GraphTxn();
System.out.println(g.find().toList().size()); // if g.size() no exception
g.begin(TxnType.READ);
System.out.println(g.size());
g.end();
```
```
org.apache.jena.sparql.JenaTransactionException: Transactions cannot be nested!
at org.apache.jena.sparql.core.mem.DatasetGraphInMemory.begin(DatasetGraphInMemory.java:149)
at org.apache.jena.sparql.graph.GraphTxn.begin(GraphTxn.java:67)
at com.gitlab.sszuev.playjena.GraphTxnTest.test(GraphTxnTest.java:30)
at java.base/java.lang.reflect.Method.invoke(Method.java:577)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
```
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "sszuev (via GitHub)" <gi...@apache.org>.
sszuev commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892473113
5.0.0-SNAPSHOT
as you said before `toList()` should cause an exception ?
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "rvesse (via GitHub)" <gi...@apache.org>.
rvesse commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892179687
> this test works without exception in early versions, for example, 4.7.0
>
> perhaps it has always worked incorrectly? If so, it would be a surprise to end users.
Yes, that's related to your discussion in #1961 which @afs addressed in #1964. In earlier releases of Jena the `GraphTxn.find()` was not run in a transaction at all.
Sometimes bugs exist silently for a long time before a user/developer spots e.g. #2150 was only recently reported by a user and I complete coincidentally also hit another instance of that bug in the same week. That's just the nature of any sufficiently large software project
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "rvesse (via GitHub)" <gi...@apache.org>.
rvesse commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892461884
> One more exception. This time "Transactions cannot be nested!"
>
> ```
> GraphTxn g = new GraphTxn();
> System.out.println(g.find().toList().size()); // if g.size() no exception
>
> g.begin(TxnType.READ);
> System.out.println(g.size());
> g.end();
> ```
>
> ```
> org.apache.jena.sparql.JenaTransactionException: Transactions cannot be nested!
>
> at org.apache.jena.sparql.core.mem.DatasetGraphInMemory.begin(DatasetGraphInMemory.java:149)
> at org.apache.jena.sparql.graph.GraphTxn.begin(GraphTxn.java:67)
> at com.gitlab.sszuev.playjena.GraphTxnTest.test(GraphTxnTest.java:30)
> at java.base/java.lang.reflect.Method.invoke(Method.java:577)
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
> at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
> ```
In which Jena version? 5.0.0-SNAPSHOT?
I guess the returned iterator isn't aware that `toList()` effectively consumes it so it isn't `close()`'d and thus never terminates the automatically begun transaction?
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Re: [I] [GraphTxn] upgrade 4.10.0 -> 5.0.0-SNAPSHOT: JenaTransactionException [jena]
Posted by "afs (via GitHub)" <gi...@apache.org>.
afs commented on issue #2195:
URL: https://github.com/apache/jena/issues/2195#issuecomment-1892776947
The `Txn` allows transaction-in-transaction. It is not full nested transactions. It tests whether the original outer transaction permits the inner one. Only committing the outer one will commit the externally visible transaction.
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