Re: [Bigdata-developers] BLZG-852 and MINUS, possible workaround

[Michael S. <ms...@me...>]

As documented in the ticket, this defect was still around in 2.0, but I fixed this MINUS+UNION combination problem now. Remaining problems should only be for edge cases (i.e., if the left-side and right-side variables that are bound at runtime are disjoint (in that case, MINUS should *not* have an effect as compared to FILTER NOT EXISTS, but does, see also http://www.w3.org/TR/sparql11-query/#neg-notexists-minus <http://www.w3.org/TR/sparql11-query/#neg-notexists-minus> and my comments in the ticket). 

Jeremy, please let us know if these edge cases are high prio for you (I’d expect these edge cases to occur very rarely in practice).

Best,
Michael

> On 28 Dec 2015, at 19:34, Bryan Thompson <br...@sy...> wrote:
> 
> Jeremy,
> 
> Have you tested this issue in the 2.0 Candidate Release?
> 
> Thanks,
> Bryan
> 
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> Bryan Thompson
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> 
> On Thu, Dec 24, 2015 at 2:42 PM, Jeremy J Carroll <jj...@sy... <mailto:jj...@sy...>> wrote:
> 
> I added a comment to this ticket with a possible workaround.
> 
> We have continued performance issues with FILTER NOT EXISTS and initial trials seem to be showing better performance with MINUS, but we are nervous about the correctness issues.
> 
> The workaround ensures there is always at least one shared variable between every binding, which IIRC, avoids the problem case.
> 
> Jeremy
> 
> 
> 
> 
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