Cypher query loading complex CSV file - cypher

Question

I have been experimenting with Cypher to load a collection of CSV files to build a view of VMware's operational state. I'm able to execute the following query:
LOAD CSV WITH HEADERS FROM 'file:///Users/rmorgan/Downloads/All_vm_hierrachy.csv' as csvline
with csvline
where csvline.type = 'VirtualMachine'
MERGE (host:HostSystem { name: csvline.hostid, description: csvline.hosttype })
MERGE (pool:ResourcePool { name: csvline.resourcePool})
MERGE (parent:Folder { name: csvline.parentid, description: csvline.parenttype })
MERGE (vm:VirtualMachine { name: csvline.moid, description: csvline.name })
CREATE (host)-[:HAS_VM]->(vm)
CREATE (vm)-[:HAS_PARENT]->(parent)
CREATE (vm)-[:HAS_RESOURCEPOOL]->(pool);
This loads details about the host, I find the matching host object and then use SET to add more attributes.
LOAD CSV WITH HEADERS FROM 'file:///Users/rmorgan/Downloads/All_vm_hierrachy.csv' as csvline
with csvline
where csvline.type = 'HostSystem' and csvline.parenttype = 'ClusterComputeResource'
match (h:HostSystem {name:csvline.moid})
set h.fullName = csvline.name
merge (p:ClusterComputeResource {name: csvline.parentid, type: csvline.parenttype})
CREATE (p)-[:HAS_CHILD]->(h);
Both queries load the same file but instantiate different objects. Is there a way to combine them? I would like to put a CASE statement in there:
LOAD CSV WITH HEADERS FROM 'file:///Users/rmorgan/Downloads/All_vm_hierrachy.csv' as csvline
with csvline
CASE csvline.type = 'HostSystem'
// create some objects and add attributes
CASE csvline.type = 'VirtualMachine'
// create some objects and add other attributes
END
// create some common objects / attributes irrespective of the path above
I would also like to nest these to produce more complex execution paths
LOAD CSV WITH HEADERS FROM 'file:///Users/rmorgan/Downloads/All_vm_hierrachy.csv' as csvline
with csvline
CASE csvline.type = 'HostSystem'
// create host object
CASE csvline.parenttype = 'ClusterComputeResource'
// create ClusterComputeResource object, link to host
CASE csvline.parenttype = 'ComputeResource'
// create ComputeResource object, link to host
CASE csvline.type = 'VirtualMachine'
// create some objects and add other attributes
END
// create some common objects / attributes irrespective of the path above
Is this possible in Cypher? the commands seem to exist but I cannot make them work together.

Answer 1

Cool use-case.
create indexes on unique properties you merge on
e.g create index on :HostSystem(name);
don't use merge on multiple attributes, esp. on import
e.g. MERGE (host:HostSystem { name: csvline.hostid }) ON CREATE SET host.description= csvline.hosttype
Regarding your second question:
we're thinking about adding a conditional update functionality
there is a workaround
keeping your statements simpler will keep them faster
I'm currently writing a blog post about this, it is not done yet,
feel free to have a look and apply the tips:
https://dl.dropboxusercontent.com/u/14493611/load_csv_with_success.adoc
Esp. the part with the Eager loading which might affect you if you have a lot of data.
the workaround is, use a combination of filter and foreach to create a single or zero element collection of "work-items"
LOAD CSV WITH HEADERS FROM 'file:///Users/rmorgan/Downloads/All_vm_hierrachy.csv' as csvline
with csvline
foreach (line in
filter(x in [csvline] where x.type = 'HostSystem'
and x.parenttype = 'ClusterComputeResource')
| MERGE (h:HostSystem {name:line.moid})
SET h.fullName = csvline.name
MERGE (p:ClusterComputeResource {name: csvline.parentid})
ON CREATE SET p.type= csvline.parenttype
CREATE (p)-[:HAS_CHILD]->(h)
)
CASE ... WHEN THEN ELSE END is an expression.