I'm using Spring Data Neo4j in my project and I'm having issues with naming conventions for repositories.
This is a simple class containing only one field and the getters/setters
#RelationshipEntity
public class ScoredRelationship
{
protected Float score;
}
and the class below extends it with other kind of fields
#RelationshipEntity(
type = RecommenderRelTypes.GOV_CONSUMER_TO_GOV_CONSUMER_SIMILARITY)
public class GovConsumerToGovConsumerSimilarity extends ScoredRelationship
{ // Other fields}
To access the relationship, I'm using the usual repository class
public interface GovConsumerToGovConsumerSimilarityRepository extends
GraphRepository<GovConsumerToGovConsumerSimilarity>
{
public Set<GovConsumerToGovConsumerSimilarity> findByScoreGreaterThan(Float value);
public Set<GovConsumerToGovConsumerSimilarity>
findByScoreGreaterThanOrderByScoreDesc(Float value);
public Set<GovConsumerToGovConsumerSimilarity>
findTopXByScoreGreaterThanOrderByScoreDesc(int limit, Float score);
}
This code compiles well. However, whenever I'm trying to use one of the methods, Spring return a series of exception or doesn't act as intended.
F.e. #findByScoreGreaterThan(0.3f) always returns an empty set. However, invoking a findAll() and printing all the scores it actually has a lot of objects with a score greater than 0.3.
In the second and third case, it always throws an exception saying
Caused by: Unknown identifier `score`.
at org.neo4j.cypher.internal.symbols.SymbolTable.evaluateType(SymbolTable.scala:60)
at org.neo4j.cypher.internal.commands.expressions.Identifier.evaluateType(Identifier.scala:51)
at org.neo4j.cypher.internal.commands.expressions.Expression.assertTypes(Expression.scala:53)
at org.neo4j.cypher.internal.pipes.SortPipe$$anonfun$assertTypes$1.apply(SortPipe.scala:34)
at org.neo4j.cypher.internal.pipes.SortPipe$$anonfun$assertTypes$1.apply(SortPipe.scala:33)
at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
at scala.collection.immutable.List.foreach(List.scala:45)
at org.neo4j.cypher.internal.pipes.SortPipe.assertTypes(SortPipe.scala:33)
at org.neo4j.cypher.internal.pipes.PipeWithSource.<init>(PipeWithSource.scala:27)
at org.neo4j.cypher.internal.pipes.SortPipe.<init>(SortPipe.scala:29)
at org.neo4j.cypher.internal.executionplan.builders.SortBuilder.apply(SortBuilder.scala:33)
at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.prepareExecutionPlan(ExecutionPlanImpl.scala:49)
at org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.<init>(ExecutionPlanImpl.scala:33)
at org.neo4j.cypher.ExecutionEngine$$anonfun$prepare$1.apply(ExecutionEngine.scala:67)
at org.neo4j.cypher.ExecutionEngine$$anonfun$prepare$1.apply(ExecutionEngine.scala:67)
at org.neo4j.cypher.internal.LRUCache.getOrElseUpdate(LRUCache.scala:37)
at org.neo4j.cypher.ExecutionEngine.prepare(ExecutionEngine.scala:67)
at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:59)
at org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:63)
at org.neo4j.cypher.javacompat.ExecutionEngine.execute(ExecutionEngine.java:79)
at org.springframework.data.neo4j.support.query.CypherQueryEngine.parseAndExecuteQuery(CypherQueryEngine.java:61)
How could be possible? I mean, the class obviously has the score field. Also, executing the simple #findByScoreGreaterThan(float value) doesn't throw any exception, but at the same the latter method always returns an empty set.
EDIT:
These are the queries used by Spring. Actually, they seems right
Executing cypher query: START `govConsumerToGovConsumerSimilarity`=node:__types__(className="it.cerict.recommender.persistence.neo4j.GovConsumerToGovConsumerSimilarity") WHERE `govConsumerToGovConsumerSimilarity`.`score`! > {0} RETURN `govConsumerToGovConsumerSimilarity` params {0=0.3}
Executing cypher query: START `govConsumerToGovConsumerSimilarity`=node:__types__(className="it.cerict.recommender.persistence.neo4j.GovConsumerToGovConsumerSimilarity") WHERE `govConsumerToGovConsumerSimilarity`.`score`! > {0} RETURN `govConsumerToGovConsumerSimilarity` ORDER BY score DESC params {0=0.3}
EDIT2: I've also tried to change the score type from Float to float with no further improvements.
This seems to be a bug related to Spring Data Neo4j. Looking to the query executed, it is clear that it searches for nodes, while it should search for relationships.
I changed the #findByScoreGreaterThanOrderByScoreDesc() method using the #Query annotation that specifies the following Cypher query
START `govConsumerToGovConsumerSimilarity`=rel:__rel_types__(className="it.cerict.recommender.persistence.neo4j.GovConsumerToGovConsumerSimilarity") WHERE `govConsumerToGovConsumerSimilarity`.`score`! > 0.3 RETURN `govConsumerToGovConsumerSimilarity` ORDER BY `govConsumerToGovConsumerSimilarity`.`score` DESC;
Related
I know how to retrieve a bean from a service in a datafetcher:
public class MyDataFetcher implements DataFetcher {
...
#Override
public Object get(DataFetchingEnvironment environment) {
return myService.getData();
}
}
But schemas with nested lists should use a BatchedExecutionStrategy and create batched DataFetchers with get() methods annotated #Batched (see graphql-java doc).
But where do I put my getData() call then?
///// Where to put this code?
List list = myService.getData();
/////
public class MyDataFetcher implements DataFetcher {
#Batched
public Object get(DataFetchingEnvironment environment) {
return list.get(environment.getIndex()); // where to get the index?
}
}
WARNING: The original BatchedExecutionStrategy has been deprecated and will get removed. The current preferred solution is the Data Loader library. Also, the entire execution engine is getting replaced in the future, and the new one will again support batching "natively". You can already use the new engine and the new BatchedExecutionStrategy (both in nextgen packages) but they have limited support for instrumentations. The answer below applies equally to both the legacy and the nextgen execution engine.
Look at it like this. Normal DataFetcherss receive a single object as source (DataFetchingEnvironment#getSource) and return a single object as a result. For example, if you had a query like:
{
user (name: "John") {
company {
revenue
}
}
Your company resolver (fetcher) would get a User object as source, and would be expected to somehow return a Company based on that e.g.
User owner = (User) environment.getSource();
Company company = companyService.findByOwner(owner);
return company;
Now, in the exact same scenario, if your DataFetcher was batched, and you used BatchedExecutionStrategy, instead of receiving a User and returning a Company, you'd receive a List<User> and would return a List<Company> instead.
E.g.
List<User> owners = (List<User>) environment.getSource();
List<Company> companies = companyService.findByOwners(owners);
return companies;
Notice that this means your underlying logic must have a way to fetch multiple things at once, otherwise it wouldn't be batched. So your myService.getData call would need to change, unless it can already fetch data for multiple source object in one go.
Also notice that batched resolution makes sense in nested queries only, as the top level resolver can already fetch a list of object, without the need for batching.
So, I've already done this using the standard Spring Data JPA interface which extends PagingAndSortingRepository in order to achieve pagination and sorting for a REST API. The thing is, now I want to achieve the very same thing but now using just vanilla JPA and so far so good I managed to get my API to paginate but the sorting doesn't work at all. Every time I try to set the parameter (from a pageable object using pageable.getSort()) it ends with a query error (either if I just send a string as parameter like "name" or just send the sort object, it shows errors).
Here's some code:
My repo implementation:
#Override
public List<Project> findByAll(Pageable pageable) {
Query query = em.createQuery("SELECT project FROM Project project ORDER BY :sort");
query.setParameter("sort", pageable.getSort());
query.setMaxResults(pageable.getPageSize());
query.setFirstResult(pageable.getPageSize() * pageable.getPageNumber());
return query.getResultList();
}
My service:
#Override
public Page<Project> findAll(Pageable pageable) {
objects = Lists.newArrayList(repository.findByAll(pageable));
PageImpl<Project> pages= new PageImpl<Project>(objects, pageable, repository.count());
return pages;
}
To be clear, I'm filling the Pageable object via URI and from the console I can say it's actually getting the data, so I assume the problem is with the repo.
Edit: This is the error I get when I replace the setParameter("sort", ...) for a hardcoded string aka query.setParameter("sort", "name"):
java.lang.NumberFormatException: For input string: "name"
And I think this method should stand for strings as well. If I use query.setParameter("sort", pageable.getSort()), the error is the same.
The order by cannot be set as a query parameter. Also, the Pageable.getSort().toString() likely won't return a string suitable for use in an order by clause as it will result in a String that represents the Order as property: ORDER, note the colon.
Here are some modifications that will work, assuming Java 8...
String order = StringUtils.collectionToCommaDelimitedString(
StreamSupport.stream(sort.spliterator(), false)
.map(o -> o.getProperty() + " " + o.getDirection())
.collect(Collectors.toList()));
Query query = em.createQuery(
String.format("SELECT project FROM Project project ORDER BY %s", order));
I have a problem with sliced access to some #DBRef field in my model. I use spring-data-mongodb-1.8.0.M1.jar
The model is like:
class Model {
....
#DBRef
List<OtherModel> members;
...
}
and I need sliced access to the members variable.
I use this query:
ObjectId objectId = new ObjectId("55c36f44f359d8a455a21f68");
Query query = new Query(Criteria.where("_id").is(objectId));
query.fields().slice("members", pageable.getOffset(), pageable.getPageSize());
List<Model> models = mongoTemplate.findOne(query, Model.class);
But I get this exception:
org.springframework.data.mapping.model.MappingException: No id property found on class class [Ljava.lang.Integer;
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.createDBRef(MappingMongoConverter.java:842)
at org.springframework.data.mongodb.core.convert.MappingMongoConverter.toDBRef(MappingMongoConverter.java:329)
at org.springframework.data.mongodb.core.convert.QueryMapper.createDbRefFor(QueryMapper.java:460)
at org.springframework.data.mongodb.core.convert.QueryMapper.convertAssociation(QueryMapper.java:417)
at org.springframework.data.mongodb.core.convert.QueryMapper.convertAssociation(QueryMapper.java:378)
at org.springframework.data.mongodb.core.convert.QueryMapper.getMappedKeyword(QueryMapper.java:257)
at org.springframework.data.mongodb.core.convert.QueryMapper.getMappedObjectForField(QueryMapper.java:200)
at org.springframework.data.mongodb.core.convert.QueryMapper.getMappedObject(QueryMapper.java:123)
at org.springframework.data.mongodb.core.MongoTemplate.doFindOne(MongoTemplate.java:1647)
at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:563)
at org.springframework.data.mongodb.core.MongoTemplate.findOne(MongoTemplate.java:558)
where a field
boolean needsAssociationConversion = property.isAssociation() && !keyword.isExists();
is set. It checks against isExists, but not against something like isSliced (which does not yet exist) and therefore is evaluated to true and, as a cause, tries to convert the non-existing association which is, in this case, just the slice-directive (an integer array). When I set the variable needsAssociationConversion to false while debugging, as if a kind of keyword.isSlice() check was done, everything works fine.
Is this a bug?
Executable project is here
https://github.com/zhsyourai/sliceDemo
I'm trying to use the IQueryOver interface of a NHibernate session object together with a LINQ expression as a criteria for selecting records in a static class. The LINQ expressions are defined in a mapping class as Expression<Func<T, object>> to get a value for an object T:
public void SearchParameter(Expression<Func<T, object>>)
These parameters get added by extending the mapping class:
public MyMapping : FindMap<MyNHibernateMappedObject>
{
public MyMapping()
{
this.SearchParameter(x => x.SomeColumn);
}
}
My Find class defines static methods for getting the previous and next record of the same type on the time axis. Each search parameter has to be identical in both records.
The Find class gets the search parameters from the mapping configuration and compiles the expressions with .Compile(). So I have the GetQueryWithSearchParameters method:
private static Func<T, object> searchParameter;
...
public static IQueryOver<T, T> GetQueryWithSearchParameters(ISession session, T current)
{
var query = session.QueryOver<T>()
.Where(x => searchParameter(x) == searchParameter(current));
return query;
}
However when building the query, I get the following exception:
System.InvalidOperationException: variable 'x' of type MyNHibernateMappedObject' referenced from scope '', but it is not defined
I don't know exactly what is going on here, but I suspect that x is not available in the delegate somehow. What am I doing wrong here?
session.QueryOver().Where(...) takes an expression, so it's going to try evaluate your expression and translate it to a query - ie. it will try to convert searchParameter(x) == searchParameter(current) into a SQL query, which it won't know how to do.
To get this to work you will need to construct the expression in code (not using a lambda expression). However I think that this is going to be a painful exercise and I think you will find it much easier to build a Criterion and add that to the QueryOver.
I have an entity that I'd like to compare with a subset and determine to select all except the subset.
So, my query looks like this:
Products.Except(ProductsToRemove(), new ProductComparer())
The ProductsToRemove() method returns a List<Product> after it performs a few tasks. So in it's simplest form it's the above.
The ProductComparer() class looks like this:
public class ProductComparer : IEqualityComparer<Product>
{
public bool Equals(Product a, Product b)
{
if (ReferenceEquals(a, b)) return true;
if (ReferenceEquals(a, null) || ReferenceEquals(b, null))
return false;
return a.Id == b.Id;
}
public int GetHashCode(Product product)
{
if (ReferenceEquals(product, null)) return 0;
var hashProductId = product.Id.GetHashCode();
return hashProductId;
}
}
However, I continually receive the following exception:
LINQ to Entities does not recognize
the method
'System.Linq.IQueryable1[UnitedOne.Data.Sql.Product]
Except[Product](System.Linq.IQueryable1[UnitedOne.Data.Sql.Product],
System.Collections.Generic.IEnumerable1[UnitedOne.Data.Sql.Product],
System.Collections.Generic.IEqualityComparer1[UnitedOne.Data.Sql.Product])'
method, and this method cannot be
translated into a store expression.
Linq to Entities isn't actually executing your query, it is interpreting your code, converting it to TSQL, then executing that on the server.
Under the covers, it is coded with the knowledge of how operators and common functions operate and how those relate to TSQL. The problem is that the developers of L2E have no idea how exactly you are implementing IEqualityComparer. Therefore they cannot figure out that when you say Class A == Class B you mean (for example) "Where Person.FirstName == FirstName AND Person.LastName == LastName".
So, when the L2E interpreter hits a method it doesn't recognize, it throws this exception.
There are two ways you can work around this. First, develop a Where() that satisfies your equality requirements but that doesn't rely on any custom method. In other words, test for equality of properties of the instance rather than an Equals method defined on the class.
Second, you can trigger the execution of the query and then do your comparisons in memory. For instance:
var notThisItem = new Item{Id = "HurrDurr"};
var items = Db.Items.ToArray(); // Sql query executed here
var except = items.Except(notThisItem); // performed in memory
Obviously this will bring much more data across the wire and be more memory intensive. The first option is usually the best.
You're trying to convert the Except call with your custom IEqualityComparer into Entity SQL.
Obviously, your class cannot be converted into SQL.
You need to write Products.AsEnumerable().Except(ProductsToRemove(), new ProductComparer()) to force it to execute on the client. Note that this will download all of the products from the server.
By the way, your ProductComparer class should be a singleton, like this:
public class ProductComparer : IEqualityComparer<Product> {
private ProductComparer() { }
public static ProductComparer Instance = new ProductComparer();
...
}
The IEqualityComparer<T> can only be executed locally, it can't be translated to a SQL command, hence the error