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Re: [rdf4j-dev] Question about READ_UNCOMMITTED
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Hi James,
I’ll make a PR.
And good news. I’ve added a transaction wrapper that buffers all added and removed statements. This means that my new memory store now supports READ_COMMITTED. It can most likely be extended to SNAPSHOT_READ the same way as the current memory store does it (by transaction numbers on the statement).
Håvard
> On 24 Jul 2017, at 17:35, James Leigh <james.leigh@xxxxxxxxxxxx> wrote:
>
> Hi Håvard,
>
> It looks like the test in wrong. I think it was originally written
> before isolation levels and should be skipped for READ_UNCOMMITTED as
> well.
>
> Can you create a PR for this?
>
> Thanks,
> James
>
> On Sat, 2017-07-22 at 16:28 +0200, Håvard Ottestad wrote:
>> Hi,
>>
>> There is a test in RepositoryConnectionTest called testEmptyCommit().
>> This test seems to do the following:
>>
>> - Create two connections
>> - Add data to one of the connections
>> - Make sure the other connection doesn’t see said data
>>
>> This test is being run at READ_UNCOMMITTED isolation level. I’m
>> wondering then if the definition of READ_UNCOMMITTED is correct.
>>
>> The current definition is:
>> /**
>> * Read Uncommitted: transactions can be rolled back, but not
>> necessarily isolated: concurrent
>> * transactions might see each other's uncommitted data (so-called
>> 'dirty reads')
>> */
>>
>> From the test I wonder if READ_UNCOMMITTED is actually meant to be a
>> snapshot isolation against other transactions adding data after a
>> READ_UNCOMMITTED connection has opened? So you can do dirty reads,
>> but only from writes that happened before the connection was opened.
>>
>> Håvard
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