Hi,
I would like to share gremlin querying using the .Net Neo4jClient.
Consider the following graph
The object is to produce a table of results that shows
- ReferralDate (ReferralDecisionSection Node)
- ReferralId (Referral Node)
- FamilyName (User Node)
- GivenName (User Node)
- The trick is we want to get all referrals but we also what referrals that do not have a who section, so the ReferralDate will be NULL. We also want to get referrals that are indirectly linked to a program (via a decision) but we also want the ones that are not indirectly linked to a program
| ReferralDate | ReferralId | FamilyName | GivenName |
| 13 Jan 2012 | 1 | Derbynew | Romiko |
| NULL | 2 | Derbynew | Romiko |
So, what we doing is essentially left/right joins on ReferralNode, ReferralDecisionNode and Program.
Lets see how we can do this in .Net Neo4jClient
return graphClient
.RootNode
.CopySplitV<Referral>((
new IdentityPipe()
.Out(Hosts.TypeKey, a => a.Key == userIdentifier.AgencyKey)
.In(UserBelongsTo.TypeKey, u => u.Username == userIdentifier.Username)
.Out(UserLinkedToProgram.TypeKey, p => p.Name == "Foundation")
.In(HasSuggestedProgram.TypeKey)
.In(ReferralHasDecisionsSection.TypeKey, r => r.Completed == false)
.AggregateV("ReferralWithProgramFoundation"),
new IdentityPipe()
.Out(Hosts.TypeKey, a => a.Key == userIdentifier.AgencyKey)
.In(ReferralBelongsTo.TypeKey, r => r.Completed == false)
)
.FairMerge()
.ExceptV("ReferralWithProgramFoundation")
.GremlinDistinct()
.Out(ReferralHasWhoSection.TypeKey)
.As("ReferralDate")
.In(ReferralHasWhoSection.TypeKey)
.As("ReferralId")
.Out(CreatedBy.TypeKey, u => u.Username == userIdentifier.Username)
.As("UserGivenName")
.As("UserFamilyName")
.Table(
who => who.ReferralDate,
referral => referral.UniqueId,
user => user.FamilyName,
user => user.GivenName
);
Notice the following
- CopySplit uses a concept of an identity pipe as a continuation of the previous output
- CopySplit will execute the two queries in parallel
- We are getting all the referrals in the system and then we are getting all the referrals in the system that have a program “Foundation”
- We then store the referrals that have a program (“Foundation”) in a aggregate (variable)
- We merge the parallel query results together with a FaireMerge
- We exclude referrals that in a a Program called “Foundation” with an Except
- We then deduplicate results with GremlinDistinct
- We then use AS to mark areas we need for table projections
Note: Using the AS clause within a CopySplit pipe in conjunction with table projections will produce undesired results, I am not sure if Gremlin supports such operations, if you know, please contact me.
Visit Marko Rodriguez for in depth discussions on Gremlin.
Romiko Derbynew 
Hi. I’m creating an application where I have to connect diffrent objects like activity to person, activity to company, room to building etc etc etc. As I see. Neo4j seems to be a good DB for this. How is the data stored in the DB? Is a node (i.e. person) created only once and linked n-times to other objects???? (Or is the data stored like in a document db?
As I see. It’s much easer to search in a graph db. For example: I want to get all relations (in/out) of a specific room, is much easier to query than in a rdbms. Am I right?
Where can I find examples/tutorials and documentations about neo4jclient? I need them VERY quick 🙂
Hi,
No problem, here we go.
http://skillsmatter.com/podcast/nosql/neo4j-dotnet
THanks!!!! Just watched the first 15min and it’s exactly what I need 🙂
Me again… I want to search for nodes of a specific type (person). For this, I want to create a “person”-index. Is it possible to execute a “LIKE/CONTAINS” query on a index?
For example: … WHERE FirstName LIKE ‘%123%’
What is the name of this function?
Thanks!
Yes, you can, use the built in Lucene Full text Search =D
public ClientSearchResultSet SearchClients(string agencyKey, ClientSearchCriteria clientSearchCriteria, int pageNumber)
{
const int pageSize = ConfigConstants.ClientSearchCountPerPage;
var utcNow = timeService.DateTimeNowUtc();
var fullclientNodes = new Node[] {};
if (clientSearchCriteria.DoesAtLeastOneFieldHaveAValue)
{
IEnumerable<Node> clientNodes;
var searchQuery = BuildSearchQueryFromCriteria(clientSearchCriteria, utcNow);
if (string.IsNullOrWhiteSpace(searchQuery))
{
clientNodes = Enumerable.Empty<Node>().ToArray();
}
else
{
var agency = agencyService.GetAgencyByKey(agencyKey);
var indexName = IndexNames.Clients(agency.Data);
fullclientNodes = graphClient
.QueryIndex(indexName, IndexFor.Node, searchQuery)
.ToArray();
clientNodes=fullclientNodes.Take(ConfigConstants.ClientSearchCountPerPage * ConfigConstants.ClientSearchMaxPages);
}
var resultsNotSorted = clientNodes
.Select(c => BuildClientSearchResult(c, utcNow));
var list = resultsNotSorted.ToList();
if (!string.IsNullOrWhiteSpace(clientSearchCriteria.FamilyName) ||
!string.IsNullOrWhiteSpace(clientSearchCriteria.GivenName))
list.Sort(new ClientNameComparator(clientSearchCriteria));
if (clientSearchCriteria.DateOfBirth != null || clientSearchCriteria.Age != null || clientSearchCriteria.Gender != null)
list.Sort(new ClientDobAgeGenderComparator(clientSearchCriteria));
var results = list.Skip((pageNumber – 1) * pageSize)
.Take(pageSize)
.ToList();
return new ClientSearchResultSet
{
Results = results,
TotalResultCount = fullclientNodes.Count(),
SearchQuery = searchQuery
};
}
var clientsQuery = graphClient
.RootNode
.Out(Hosts.TypeKey, a => a.Key == agencyKey)
.In(ClientBelongsTo.TypeKey)
.GremlinSkip(0)
.GremlinTake(ConfigConstants.ClientSearchCountPerPage * ConfigConstants.ClientSearchMaxPages);
var totalClients = graphClient
.RootNode
.Out(Hosts.TypeKey, a => a.Key == agencyKey)
.In(ClientBelongsTo.TypeKey)
.GremlinCount();
var fullresultsnotsorted = clientsQuery
.Select(c => BuildClientSearchResult(c, utcNow))
.ToList();
fullresultsnotsorted.Sort(new ClientIdComparator());
var fullresults = fullresultsnotsorted.Skip((pageNumber – 1) * pageSize)
.Take(pageSize)
.ToList();
return new ClientSearchResultSet
{
Results = fullresults,
TotalResultCount = totalClients,
SearchQuery = clientsQuery.QueryText
};
}
public NodeReference CreateClient(Client client, Node agencyNode, IEnumerable indexEntries)
{
var uniqueIdGenerator = uniqueIdGeneratorCallback();
client.UniqueId = uniqueIdGenerator.NextId(UniqueIdScopes.Clients(agencyNode.Data));
var clientNodeReference = graphClient.Create(
client,
new[] { new ClientBelongsTo(agencyNode.Reference) },
indexEntries);
return clientNodeReference;
}