Re: [Virtuoso-users] Complex SPARQL query - Performance hints?

Lorena Etcheverry Wed, 28 Sep 2016 07:36:12 -0700

Hi Pantelis:

Do you really need to use the REGEX ignore case feature?
If not, you can substitute some of your FILTER expressions by BGPs.

For example, replacing:

GRAPH <GraphCURI>{
     ?variableI <http://www.w3.org/2004/02/skos/core#notation> ?variableJ .
     ?variableI <http://www.w3.org/2004/02/skos/core#prefLabel> ?variableK .
    FILTER (isLiteral(?variableK) && REGEX(?variableK, "literalA", "i"))

by

GRAPH <GraphCURI>{
     ?variableI <http://www.w3.org/2004/02/skos/core#notation> ?variableJ .
     ?variableI <http://www.w3.org/2004/02/skos/core#prefLabel> "literalA" .
}

best
Lorena

On 28/09/16 10:13, Peter Lawrence wrote:

Another observation I note is that there is a common factor within each UNION:

GRAPH <GraphABaseURI>{

?variableA a graphA:ClassA .

?variableA graphA:propertyA ?variableB .

?variableB dcterms:title ?variableC .

?variableA graphA:propertyB ?variableD .}

Could this be factored out to drive the overall query, and then UNION the sub-selects on the other conditions?

On Wed, Sep 28, 2016 at 2:06 PM Jerven Tjalling Bolleman <jerven.bolleman@sib.swiss> wrote:

Hi Pantelis,

One thing that struck me as an other virtuoso user is
the joins in the filters.

e.g.

FILTER (?variableE = ?variableH)

I think if you remove all instances of ?variableH with ?variableE
you should get better results.

Hope that helps.

Regards,
Jerven

On 28/09/16 14:44, Pantelis Natsiavas wrote:
> Hi everybody.
>
> I have a rather complex SPARQL query, which is executed thousands of
> times in parallel threads (400 threads). The query is here somewhat
> simplified (namespaces, properties and variables have been reduced) for
> readability, but the complexity is left untouched (unions, number of
> graphs etc.). The query is run against 4 graphs, the biggest of which
> contains 5561181 triples.
>
> PREFIX graphA: <GraphABaseURI:>
>
> ASK
> FROM NAMED <GraphBURI>
> FROM NAMED <GraphCURI>
> FROM NAMED <GraphABaseURI>
> FROM NAMED <GraphDBaseURI>
> WHERE{
> {
> GRAPH <GraphABaseURI>{
> ?variableA a graphA:ClassA .
> ?variableA graphA:propertyA ?variableB .
> ?variableB dcterms:title ?variableC .
> ?variableA graphA:propertyB ?variableD .
> ?variableL<GraphABaseURI:propertyB> ?variableD .
> ?variableD <propertyBURI> ?variableE
> }
> .
> GRAPH <GraphBURI>{
> ?variableF <propertyCURI>/<propertyDURI> ?variableG .
> ?variableF <propertyEURI> ?variableH
> }
> .
> GRAPH <GraphCURI>{
> ?variableI <http://www.w3.org/2004/02/skos/core#notation>
> ?variableJ .
> ?variableI <http://www.w3.org/2004/02/skos/core#prefLabel>
> ?variableK .
> FILTER (isLiteral(?variableK) && REGEX(?variableK, "literalA", "i"))
> }
> .
> FILTER (isLiteral(?variableJ) && ?variableG = ?variableJ) .
> FILTER (?variableE = ?variableH)
> }
> UNION
> {
> GRAPH <GraphABaseURI>{
> ?variableA a graphA:ClassA .
> ?variableA graphA:propertyA ?variableB .
> ?variableB dcterms:title ?variableC .
> ?variableA graphA:propertyB ?variableD .
> ?variableL<propertyBURI> ?variableE .
> ?variableL <propertyFURI> ?variableD .
> }
> .
> GRAPH <GraphDBaseURI>{
> ?variableM <propertyGURI> ?variableN .
> ?variableM <propertyHURI> ?variableO .
> FILTER (isLiteral(?variableO) && REGEX(?variableO, "literalA",
> "i"))
> }
> .
> FILTER (?variableE = ?variableN) .
>
> }
> UNION
> {
> GRAPH <GraphABaseURI>{
> ?variableA a graphA:ClassA .
> ?variableA graphA:propertyA ?variableB .
> ?variableB dcterms:title ?variableC .
> ?variableA graphA:propertyB ?variableD .
> ?variableL<propertyBURI> ?variableE .
> ?variableL <propertyIURI> ?variableD .
> }
> .
> GRAPH <GraphDBaseURI>{
> ?variableM <propertyGURI> ?variableN .
> ?variableM <propertyHURI> ?variableO .
> FILTER (isLiteral(?variableO) && REGEX(?variableO, "literalA",
> "i"))
> }
> .
> FILTER (?variableE = ?variableN) .
> }
> . FILTER (isLiteral(?variableC) && REGEX(?variableC, "literalB",
> "i")) .
> }
>
>
> I would not expect someone to transform the above query (of course...).
> I am only posting the query to demonstrate the complexity and all the
> SPARQL structures used.
>
> My questions:
>
> 1. Would I gain regarding performance if I had all my triples in one
> graph? This way I would avoid unions and simplify my query, however,
> would this also benefit in terms of performance?
> 2. Are there any kind of indexes that I could built and they could be of
> any help with the above query? I am not really confident on data
> indexing, however reading in
> http://virtuoso.openlinksw.com/dataspace/doc/dav/wiki/Main/VirtRDFPerformanceTuning#RDF
> Index Scheme I wonder if the virtuoso 7's default indexing scheme is
> suitable for queries like the above. While the predicates are defined in
> the above query's SPARQL triple patterns, there are many triple patterns
> that have not defined subject or predicate. Could this be a major
> problem regarding performance?
> 3. Perhaps there is a SPARQL syntax structure that I am not aware of and
> could be of great help in the above query. Could you suggest something?
> For example, I have already improved performance by removing STR() casts
> and using the isLiteral() function. Could you suggest anything else?
> 4. Perhaps you could suggest overusing a complex SPARQL syntax structure?
>
> Please note that I use Virtuoso Open source edition, built on Ubuntu,
> Version: 07.20.3214, Build: Oct 14 2015.
>
> Regards,
> Pantelis Natsiavas
>
>
>
> ------------------------------------------------------------------------------
>
>
>
> _______________________________________________
> Virtuoso-users mailing list
> Virtuoso-users@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/virtuoso-users
>

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Re: [Virtuoso-users] Complex SPARQL query - Performance hints?

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