Indexing of fulltext properties from cypher and unique relationships

Why are you hiding?

Issues from the previous post aside, I needed to import some data from CSV. That went surprisingly painless (well, the first part anyway...) - but despite having an index on one of the fields in the class, after some testing I realized that I couldn't find my entities by that field.

My class mapping looked something like:

public class City extends GraphNode {

    @Indexed(indexType = IndexType.FULLTEXT, indexName = "locations")
    private String name;
...
}

My cypher import (note the extra labels for SDN):

String cypher = "LOAD CSV WITH HEADERS FROM \"" + fileLocation + "\" AS csvLine "
+ "MERGE (country:Country:_Country { name: csvLine.Country } ) "
+ "MERGE (city:City:_City { name: csvLine.City } ) "
+ "MERGE (city) - [:IS_IN] -> (country) "
+ "MERGE (airport:Airport:_Airport {name: csvLine.Airport, iataCode: csvLine.IATAcode, icaoCode: csvLine.ICAOcode} ) "
+ "MERGE (airport) - [:SERVES {__type__: 'AirportCityConnection'}] -> (city) "

SDN repository I used for testing:

public interface CityRepository extends GraphRepository {

    Page findByNameLike(String name, Pageable page);
    
    List findByName(String cityName);
}

I had a test for the repository and the lookup worked fine when data was inserted via SDN but not with my CSV Cypher import. With the help of brilliant Michael Hunger I managed to find a reason and workaround. For details of why the next step is needed check Michael's explanation, if all you want is to make it work, for now you'll need to do something like this:

String cypher = "LOAD CSV WITH HEADERS FROM \"" + fileLocation + "\" AS csvLine "
+ "MERGE (country:Country:_Country { name: csvLine.Country } ) "
+ "MERGE (city:City:_City { name: csvLine.City } ) "
+ "MERGE (city) - [:IS_IN] -> (country) "
+ "MERGE (airport:Airport:_Airport {name: csvLine.Airport, iataCode: csvLine.IATAcode, icaoCode: csvLine.ICAOcode} ) "
+ "MERGE (airport) - [:SERVES {__type__: 'AirportCityConnection'}] -> (city) "
+ "RETURN city";
Result cities = neo4jTemplate.query(cypher, ImmutableMap.of()).to(Node.class);
Index index = db.index().forNodes("locations");
for (Node city : cities) {
    String location = (String) city.getProperty("name");
    index.remove(city);
    index.add(city, "name", location);
}

Modelling marriage relationship

Well, in all honesty I was actually modelling a flight schedule but the same principle applies - you cannot fly out from two airports at the same time on the same flight number. Yet (with the help of Excel autocomplete feature, which changed flight code QF1 into QF10...) I managed to create data that implied that this can actually happen. My SDN model was not taking this situation into account and cried not-so-silently when I tried to retrieve the data from Neo4j

java.lang.IllegalArgumentException: Cannot obtain single field value for field 'to'
 at org.springframework.data.neo4j.fieldaccess.RelatedToSingleFieldAccessorFactory$RelatedToSingleFieldAccessor.getValue(RelatedToSingleFieldAccessorFactory.java:94)
 at org.springframework.data.neo4j.fieldaccess.DefaultEntityState.getValue(DefaultEntityState.java:97)

So a quick tip is - if you want to avoid bigamy in your database (and this exception) - make sure you're not making node A married to B and C at the same time.

Stay tuned for more Neo4j drama. :)