apoc.meta.graph
Procedure APOC Core
apoc.meta.graph - examines the full graph to create the meta-graph
Signature
apoc.meta.graph(config = {} :: MAP?) :: (nodes :: LIST? OF NODE?, relationships :: LIST? OF RELATIONSHIP?)Config parameters
This procedure supports the following config parameters:
| Name | Type | Default | Description |
|---|---|---|---|
sample |
Long |
1 |
Number of nodes to skip, e.g. a sample of 1000 will read every 1000th node. Defaults to read every node. |
maxRels |
Long |
-1 |
Number of relationships to read per sampled node. A value of -1 will read all. |
Sampling
This procedure works by using the database statistics. A new node is returned for each label, and its connecting relationships are calculated based on the pairing combinations of [:R]→(:N) and (:M)→[:R]. For example, for the graph (:A)-[:R]→(:B)-[:R]→(:C), the path (:B)-[:R]→(:B) will be calculated from the combination of [:R]→(:B) and (:B)-[:R]. This procedure will post-process the data by default, removing all non-existing relationships. This is done by scanning the nodes and their relationships. If the relationship is not found, it is removed from the final result. This slows down the procedure, but will produce an accurate schema.
See apoc.meta.graphSample to avoid performing any post-processing.
It is also possible to specify how many nodes and relationships to scan. The config parameter sample gives the skip count,
and the maxRels parameter gives the max number of relationships that will be checked per node.
If sample is set to 100, this means that every 100th node will be checked per label,
and a value of 100 for maxRels means that for each node read, only the first 100 relationships will be read.
Note that if these values are set, and the relationship is not found within those constraints,
it is assumed that the relationship does not exist, and this may result in false negatives.
A sample value higher than the number of nodes for that label will result in one node being checked.
Usage Examples
The examples in this section are based on the following sample graph:
CREATE (Keanu:Person {name:'Keanu Reeves', born:1964})
CREATE (TomH:Person {name:'Tom Hanks', born:1956})
CREATE (TheMatrix:Movie {title:'The Matrix', released:1999, tagline:'Welcome to the Real World'})
CREATE (TheMatrixReloaded:Movie {title:'The Matrix Reloaded', released:2003, tagline:'Free your mind'})
CREATE (TheMatrixRevolutions:Movie {title:'The Matrix Revolutions', released:2003, tagline:'Everything that has a beginning has an end'})
CREATE (SomethingsGottaGive:Movie {title:"Something's Gotta Give", released:2003})
CREATE (TheDevilsAdvocate:Movie {title:"The Devil's Advocate", released:1997, tagline:'Evil has its winning ways'})
CREATE (YouveGotMail:Movie {title:"You've Got Mail", released:1998, tagline:'At odds in life... in love on-line.'})
CREATE (SleeplessInSeattle:Movie {title:'Sleepless in Seattle', released:1993, tagline:'What if someone you never met, someone you never saw, someone you never knew was the only someone for you?'})
CREATE (ThatThingYouDo:Movie {title:'That Thing You Do', released:1996, tagline:'In every life there comes a time when that thing you dream becomes that thing you do'})
CREATE (CloudAtlas:Movie {title:'Cloud Atlas', released:2012, tagline:'Everything is connected'})
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrix)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixReloaded)
CREATE (Keanu)-[:ACTED_IN {roles:['Neo']}]->(TheMatrixRevolutions)
CREATE (Keanu)-[:ACTED_IN {roles:['Julian Mercer']}]->(SomethingsGottaGive)
CREATE (Keanu)-[:ACTED_IN {roles:['Kevin Lomax']}]->(TheDevilsAdvocate)
CREATE (TomH)-[:ACTED_IN {roles:['Joe Fox']}]->(YouveGotMail)
CREATE (TomH)-[:ACTED_IN {roles:['Sam Baldwin']}]->(SleeplessInSeattle)
CREATE (TomH)-[:ACTED_IN {roles:['Mr. White']}]->(ThatThingYouDo)
CREATE (TomH)-[:ACTED_IN {roles:['Zachry', 'Dr. Henry Goose', 'Isaac Sachs', 'Dermot Hoggins']}]->(CloudAtlas);CALL apoc.meta.graph()