Optimized queries through R2RML/Virtual Graph

[Charbel Kaed]

Hello,

I would like to have your opinion on what is the best way to execute a federated query combining a local table in Stardog and a remote RDBMS through R2RML. The remote table contains 50 million records and the result of the query is expected to return between 500.000 and 1 million records.

SELECT DISTINCT ?b ?ts ?val 

WHERE {

 ?point qt:hasSeries ?id. //this should return 40 ids.

graph <virtual://semantic> // this should return 500.000 and 1 million records after the filter on the ids.

 {

   [] qt:hasSeries ?b; 

      qt:hasV ?val ; 

      qt:hasT ?ts.  

      filter(?val <5). 

 } 

filter (?id = ?b) 

} 

group by ?b ?ts ?val

Thank you,

Charbel.

[Zachary Whitley]

The most straight forward solution would be materializing the virtual graph and loading the data into Stardog.

I don't know if you can use variables with virtual graphs but if you can and there aren't too many total id's you might be able to create a separate mapping for each series ?id and add some information that correlates id with the virtual graph. Not a great solution but might work. I'd be interested to know if you can use variables with virtual graphs. You can't with service url's but I virtual graphs might work.

I'm assuming there isn't anything you can do from the RDBMS side. If there is you might be able to create a user defined function that turns the query inside out and makes a sparql call from the RDBMS depending on the database you're using.

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[Zachary Whitley]

I just came across this project [1] that looks like it implements what I suggested with calling Stardog from the relational database. It's using MS SQL Server and Stardog. I don't recall you mentioning what RDBMS you were using. 

[1] https://github.com/ronmichael/stardog-bites-mssql/blob/master/README.md

stardog+u...@clarkparsia.com

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[charbel kaed]

Thank you Zachary, 
I will take a look at it.

On Thu, Oct 20, 2016 at 8:02 PM, Zachary Whitley <zachary...@gmail.com> wrote:

I just came across this project [1] that looks like it implements what I suggested with calling Stardog from the relational database. It's using MS SQL Server and Stardog. I don't recall you mentioning what RDBMS you were using. 

[1] https://github.com/ronmichael/stardog-bites-mssql/blob/master/README.md

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