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openRDF.org Forum » Sesame & Rio: Open Discussion » Thread: SPARQL syntax effects speed

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Sep 16, 2007 2:28:59 AM

hendlerman
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Joined: Sep 14, 2004
Posts: 36
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SPARQL syntax effects speed

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I seemed to have gained quite a lot of time by moving a FILTER to the end of a SPARQL statement instead of the beginning. This would make sense since the first statement in the query would be more efficient than a FILTER - but I wanted to make sure I wasn't imagining this.


//find grammy and grandpa

//was like
?subject ?p ?o .
FILTER(REGEX(str(?object),"^gra")) .
?subject ns:hasnick ?object .

//is now
?subject ?p ?o .
?subject ns:hasnick ?object .
FILTER(REGEX(str(?object),"^gra")) .

Also, obviously, OPTIONALS are slower, and it may be faster to retrieve additional data as a separate query. Is this also a common finding among users?
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[Edit 2 times, last edit by hendlerman at Sep 16, 2007 3:17:34 AM]

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Sep 17, 2007 4:03:46 PM

arjohn
OpenRDF project lead

The Netherlands
Joined: Jan 23, 2004
Posts: 1289
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Re: SPARQL syntax effects speed

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//find grammy and grandpa

//was like
?subject ?p ?o .
FILTER(REGEX(str(?object),"^gra")) .
?subject ns:hasnick ?object .

//is now
?subject ?p ?o .
?subject ns:hasnick ?object .
FILTER(REGEX(str(?object),"^gra")) .

I can't quite explain the difference. Both queries are parsed to the exact same query model so query evaluation performance should be identical. There must be some other reason for the difference.
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Arjohn Kampman, OpenRDF project lead, Aduna

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Sep 17, 2007 6:50:15 PM

hendlerman
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Joined: Sep 14, 2004
Posts: 36
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Re: SPARQL syntax effects speed?

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I can't quite explain the difference. Both queries are parsed to the exact same query model so query evaluation performance should be identical. There must be some other reason for the difference.

The specific query I have there is not actually the query I'm doing, but it does show that I've moved the filter later in the statement. I've gotten another answer, I think, here http://www.openrdf.org/forum/mvnforum/viewthread?thread=1431#5387 saying that it may matter.

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