N10s.rdf.preview.fetch vs n10s.rdf.import.fetch

[Grant592]

Hi,

I'm trying to build a knowledge graph from Wikidata using the n10s library. When I run the following using n10s.rdf.preview.fetch I get a preview of the nodes and relationships which look correct:

WITH 'PREFIX wdt: <http://www.wikidata.org/prop/direct/>
PREFIX wd: <http://www.wikidata.org/entity/>
PREFIX sch: <http://schema.org/> 
PREFIX rdfs:  <http://www.w3.org/2000/01/rdf-schema#> 
CONSTRUCT { 
  ?band a sch:Band ; 
          sch:name ?bandName ; 
          wdt:P571 ?startYear . 
  ?member a sch:Musician ; 
            sch:name ?memberName ; 
            wdt:P463 ?band . 
  ?album a sch:Release ; 
           sch:name ?albumName ; 
           wdt:P175 ?band ; 
           wdt:P577 ?releaseDate . } 
WHERE { 
  ?band wdt:P136 wd:Q49451. 
  ?band wdt:P495 ?country ; 
        wdt:P571 ?startYear ; 
        rdfs:label ?bandName . filter (lang(?bandName) = "en") . 
  ?album wdt:P175 ?band ; 
         wdt:P577 ?releaseDate ; 
         rdfs:label ?albumName . filter (lang(?albumName) = "en") . 
  OPTIONAL {?member wdt:P463 ?band ; 
          rdfs:label ?memberName . filter (lang(?memberName) = "en") . }
  FILTER(YEAR(?startYear) <= 1980 &&  ?country IN ( wd:Q145, wd:Q38 )). SERVICE wikibase:label { bd:serviceParam wikibase:language "[AUTO_LANGUAGE]". }}' AS sparql
CALL n10s.rdf.preview.fetch(
    'https://query.wikidata.org/sparql?query=' + apoc.text.urlencode(sparql), "JSON-LD", { headerParams: { Accept: "application/ld+json"},
    handleVocabUris:"IGNORE"
    }
)
YIELD nodes, relationships
RETURN nodes, relationships

However, when I run the same code but using n10s.rdf.import.fetch I get terminationStatus: KO, triplesParsed: 0, triplesLoaded: 0

...same code...
CALL n10s.rdf.import.fetch(
    'https://query.wikidata.org/sparql?query=' + apoc.text.urlencode(sparql), "JSON-LD", { headerParams: { Accept: "application/ld+json"},
    handleVocabUris:"IGNORE"
    }
)
YIELD terminationStatus, triplesLoaded, triplesParsed
RETURN terminationStatus, triplesLoaded, triplesParsed

Can anyone help explain why preview is returning the triples but import isn't doing anything?

I'm using:
Browser version: 4.3.5
Server version: 4.2.1
Neosemantics: 4.2.0.0

Thanks!

[Grant592]

So after spending the past 48 hours trying to figure this out, and after posting my questions I finally stumbled across the answer so thought I would post back to the forum in case anyone else has the same question in future. I had not created a constraint prior to trying to run the import. Running the following code has solved my problem:

CREATE CONSTRAINT n10s_unique_uri ON (r:Resource) ASSERT r.uri IS UNIQUE

I'd been using resources from various sites and only just stumbled on this README from @jesus.barrasa .

[jesus_barrasa]

Hey @Grant592 , sorry to hear it took so long to find the answer 😞

The required constraint is described in chapter 2 of the manual "Configuring Neo4j to use RDF data". Maybe it should go in a more prominent place in the manual?

The reason why you were not seeing a more informative output message is that the extraInfo field was excluded from the output of the n10s.rdf.import.* procedure. Notice below what the YIELD+RETURN part of your query would look like when including the extra fields,

YIELD terminationStatus, triplesLoaded, triplesParsed, namespaces, extraInfo
RETURN terminationStatus, triplesLoaded, triplesParsed, namespaces, extraInfo

Hope this helps.

JB

[Grant592]

Thanks for the reply. And having looked back, I can see the piece of info I needed was there at the start of the official Neosemantics docs but because I was using various different blogs/sources I hadn't noticed this was a prerequisite to use this procedure! My own fault really.

Just getting started with Neo4j and graph databases in general, so it's nice to see the forums are such a friendly and responsive place!