On 2017-09-12 10:43, Andy Seaborne wrote:
> They are per storage area.
>
> This blocks and never prints "DONE"
>
> Location loc = Location.create("DB");
> Dataset dataset1 = TDBFactory.createDataset(loc);
> Dataset dataset2 = TDBFactory.createDataset(loc);
> dataset1.begin(ReadWrite.WRITE) ;
> dataset2.begin(ReadWrite.WRITE) ;
> System.out.println("DONE");
>
> but if either a READ, it will work - there and be many readers and one
> writer at a time. The readers will not see the updated by the writer
> even after the writer commits.
I understands that but I still think they are not liked to the storage
area. If you put
Location loc = Location.create("DB");
Dataset dataset1 = TDBFactory.createDataset(loc);
Dataset dataset2 = TDBFactory.createDataset(loc);
dataset1.begin(ReadWrite.READ) ;
System.out.println(dataset1.isInTransaction());
System.out.println(dataset2.isInTransaction());
dataset2.begin(ReadWrite.READ) ;
System.out.println("DONE");
It will print true for dataset1 and false for dataset2 cases. This means
that the transaction is linked to the object Dataset and not the real
location. Or at least this is what is happening to me.
Therefore I think this is a bug :( as the transaction READ is opened
over the same location. I haven't checked for the WRITE but I guess it
should be the same. If you write on a dataset and you have a several
transactions opened this means you will have a kind of a counter
(semaphore) and when you call the .end() you finish them.
>
> Creating the datasets is quite cheap. It is not really creating
> everything everytime. But a statics works as well; Fuseki uses a static
> registry of datasets.
>
> (it's called "connect", "not "create" in TDB2 to make that clearer).
>
> Andy
I think the static will be the way to go for me for the cleanness of the
code, as otherwise it will more complex to handle.
>
> On 11/09/17 15:57, George News wrote:
>> Hi all,
>>
>> I'm facing an issue that I guess it was implemented that way for some
>> reason. The issue is that I thought that transactions were Dataset
>> based, not the object but the TDB or whatever database you use.
>>
>> However while developing my service I have noticed that if you open 2
>> datasets on the same TDB
>>
>> Dataset dataset1 = TDBFactory.createDataset(tripleStorePath);
>> Dataset dataset2 = TDBFactory.createDataset(tripleStorePath);
>>
>> then each dataset has it's own transaction pointer, that is, read/write
>> operations are block per object. Is that the expected behaviour? Why is
>> like this and not blocked per triple store?
>>
>> Therefore my question now goes in the direction of which is better. I'm
>> developing a webservice that is working against the same triple store
>> path. The Dataset object I create on each call is link to the instance
>> of the class (not static). Then, how should I proceed? Should I create
>> the Dataset variable as static, so this way I only have one object for
>> all?
>>
>> Thanks
>> Regards,
>>
>
