The best explanation I can offer is that the optimizer does weird things sometimes, especially with subqueries: in my experience, subqueries rarely bring the optimization I expect. However, named subqueries often perform a lot better (they run exactly once). This version of your query runs in less than a second:
PREFIX wp: <http://vocabularies.
Cheers,wikipathways.org/wp#>
PREFIX dcterms: <http://purl.org/dc/terms/>
PREFIX dc: <http://purl.org/dc/elements/1.1/>
SELECT DISTINCT ?metabolite1Label ?metabolite2Label ?mass1 ?mass2 WITH {
SELECT ?metabolite1 ?metabolite2 WHERE {
?pathwayItem wdt:P2410 "WP706";
wdt:P2888 ?pwIri.
SERVICE <http://sparql.wikipathways.org/> {
?pathway dc:identifier ?pwIri.
?interaction rdf:type wp:Interaction;
wp:participants ?wpmb1, ?wpmb2;
dcterms:isPartOf ?pathway.
FILTER (?wpmb1 != ?wpmb2)
?wpmb1 wp:bdbWikidata ?metabolite1.
?wpmb2 wp:bdbWikidata ?metabolite2.
}
}
} AS %metabolites WHERE {
INCLUDE %metabolites.
?metabolite1 wdt:P2067 ?mass1.
?metabolite2 wdt:P2067 ?mass2.
SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE],en". }
}
Lucas
On 26.06.2017 21:58, Andra Waagmeester wrote:
I am puzzled by a pattern I am seeing in submitting nested SELECT statements to the WDQS.In cases where a federated query to the WDQS time out, it helps to include redundant SELECT statements for the same query to resolve.
The following query does not resolve:
results: http://tinyurl.com/ybl55tk4 When the lines 7 and 9 in the above example are duplicated, suddenly the query does resolve
results: http://tinyurl.com/y9mjkejo
What is the added value of a double SELECT (line 7,8 and line 10,11). Also the lines 5 and 9 had to be separated by a SELECT statement to be successful.
Is this an implementation issue, or am I doing something wrong?
kind regards,
Andra Waagmeester
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