RE: CMS diff: TDB Datasets

[Greg Albiston]

Hi Andy,

Thanks for the response. Your suggestion worked and the query completed in a 
similar time to the union graph approach.
I'd tried moving the filter into the graph clause but not swapping the graph 
order.

I added that update on the documentation so if anyone else was having similar 
problems it might help.
Do you still want me to create a JIRA for it?

More generally, is there a page/section for tips on query writing to help 
optimisation? 
I searched but could only find description of TDB's optimisation functionality 
and extending query execution. I spent quite a while hunting for tips and 
trying different ways to influence the resolution order until I thought I'd try 
the union graph.

Thanks,

Greg 

-----Original Message-----
From: Andy Seaborne <a...@apache.org> 
Sent: 19 June 2018 13:56
To: dev@jena.apache.org; Greg Albiston <greg_albis...@hotmail.com>
Subject: Re: CMS diff: TDB Datasets

Greg,

Could you create a JIRA ticket for this please?  It is something that looks 
addressable.  The solution proposed (using union graph) is a bit specialised.

     Andy

The query may be better if written (but the "..." may be making a
difference.)

  GRAPH dataset:SmallB {
    ?b rdf:type my:BThing.
    ?b my:hasData ?bData.
   FILTER(my:filterFunction2(?bData, "1.0 3.0, 4.0 2.0"^^my:dataLiteral)) }

GRAPH dataset:BigA {
   ?a rdf:type my:AThing.
   ?a noa:hasGeometry ?aData.
}
FILTER(my:filterFunction1(?bData, ?aData))



On 19/06/18 10:59, Greg Albiston wrote:
> Clone URL (Committers only):
> https://cms.apache.org/redirect?new=anonymous;action=diff;uri=http://j
> ena.apache.org/documentation%2Ftdb%2Fdatasets.mdtext
> 
> Greg Albiston
> 
> Index: trunk/content/documentation/tdb/datasets.mdtext
> ===================================================================
> --- trunk/content/documentation/tdb/datasets.mdtext   (revision 1833775)
> +++ trunk/content/documentation/tdb/datasets.mdtext   (working copy)
> @@ -51,6 +51,51 @@
>           ...
>       }
>   
> +### Named Graphs & Filters
> +
> +Named graphs provide a convenient way to organise and store your data.
> +However, be aware that in certain situations named graphs can make it 
> difficult for the query optimiser.
> +
> +For example, a query with the following structure took 29 minutes to 
> complete:
> +
> +    SELECT ?b ...
> +    WHERE {
> +
> +        GRAPH dataset:BigA {
> +            ?a rdf:type my:AThing.
> +            ?a noa:hasGeometry ?aData.
> +            ...
> +        }
> +     
> +        GRAPH dataset:SmallB {
> +            ?b rdf:type my:BThing.
> +            ?b my:hasData ?bData.
> +            ...                              
> +        }
> +
> +        FILTER(my:filterFunction1(?bData, ?aData))
> +        FILTER(my:filterFunction2(?bData, "1.0 3.0, 4.0 
> + 2.0"^^my:dataLiteral) )
> +
> +    }
> +
> +The completion duration was reduced to 7 seconds by applying the global 
> TDB.symUnionDefaultGraph option (see above) to the dataset and modifying the 
> query as follows:
> +
> +    SELECT ?b ...
> +    WHERE {
> +
> +        ?a rdf:type my:AThing.
> +        ?a noa:hasGeometry ?aData.
> +        ...
> +
> +        ?b rdf:type my:BThing.
> +        ?b my:hasData ?bData.
> +        ...                          
> +
> +        FILTER(my:filterFunction1(?bData, ?aData))
> +        FILTER(my:filterFunction2(?bData, "1.0 3.0, 4.0 
> + 2.0"^^my:dataLiteral) )
> +
> +    }
> +
>   ## Special Graph Names
>   
>   URI | Meaning
>