neo4j.data.quality

stored procedures to create & manage data quality flags.

Installation

• Copy the jar into Neo4j's "plugins" directory : $NEO4J_HOME/plugins
• For security reasons, procedures that use internal APIs are disabled by default. They can be enabled by specifying config in $NEO4J_HOME/conf/neo4j.conf e.g. dbms.security.procedures.unrestricted=neo4j.dq.*
• Restart Neo4j

Definitions

• flag : modelled as a DQ_Flag node, linked to a data node with a HAS_DQ_FLAG relationship, representing a data quality issue affecting that node.
• class : to help organize flags, they're given a class, which is part of a class hierarchy. The flag class is modelled as an extra node label on the flag, as well as a separate DQ_Class node linked to the flag with a HAS_DQ_CLASS relationship. Classes in the hierarchy are linked to their children/parent classes with a HAS_DQ_CLASS relationship.
• attachment : to provide more context to a DQ flag, one can attach other nodes to it (beyond the node it already links to). For example, a flag could represent a data mismatch between 2 nodes, in which case it can be useful to attach the second node to the flag.

Features

The following procedures are exposed :

• neo4j.dq.createFlag
• neo4j.dq.attachToFlag
• neo4j.dq.deleteFlag
• neo4j.dq.deleteNodeFlags
• neo4j.dq.listFlags
• neo4j.dq.listClasses
• neo4j.dq.createClass
• neo4j.dq.deleteClass
• neo4j.dq.statistics

Procedure neo4j.dq.createFlag

Creates a "data quality flag" node for the given data node.

Usage

CALL neo4j.dq.createFlag(node, label, description)

parameters

• node (Node|id) : the data node to flag.
• label (String) : label for the flag node, used to categorise the type of data quality issue. Also used for the "DQ_Class" node. Optional (defaults to "Generic_Flag").
• description (string) : property of the flag node. Optional (defaults to "").

output

• Creates a (flag:DQ_Flag:_label_) node, with the provided description=_description_ as property, and the relationship (_node_)-[:HAS_DQ_FLAG]->(flag).
• May also create, if it doesn't exist already, a (class:DQ_Class) node, with class=_label_ as property, and the relationship (flag)-[:HAS_DQ_CLASS]->(class).
• If the class node doesn't exist, it is created as a child of the root class node : (class)-[:HAS_DQ_CLASS]->(root).
• Returns the created flag node

examples

Flag all Node nodes that are missing a "state" property :

MATCH (n:Node) WHERE NOT EXISTS(n.state)
CALL neo4j.dq.createFlag(n, 'MissingState', 'nodes of type Node should have a state property') yield flag
RETURN flag

Procedure neo4j.dq.attachToFlag

Attach a data node to a flag with a HAS_ATTACHMENT relationship.

Usage

CALL neo4j.dq.attachToFlag(flagNode, node| list of nodes)

parameters

• flag (Node|id) : the flag node to attach to
• attachmentNode (Node|id) : the data node to attach
• description (String) : property of the HAS_ATTACHMENT relationship. Optional (defaults to "").

output

• Creates a relationship (_flag_)-[:HAS_ATTACHMENT]->(_node_), with description=_description_ as property of the relationship.
• Returns the HAS_ATTACHMENT relationship created.

examples

MATCH (p:Person)-[r:ACTED_IN]->(m:Movie)
WHERE NOT EXISTS(r.roles)
CALL neo4j.dq.createFlag(p, 'MissingRoles', 'Missing : ' + p.name+ ' in ' +m.title) yield flag
CALL neo4j.dq.attachToFlag(flag, m) YIELD attachment
RETURN flag, attachment

Procedure neo4j.dq.deleteFlags

Deletes flag nodes.

Usage

CALL neo4j.dq.deleteFlags(flags)

parameters

• flags (ANY: Node|[Node]|id|[ids]) : Node or list of nodes (or its/their ids) of the flag(s) to delete. Any node passed in that's not a DQ_Flag, will be ignored.
• batchSize (Long) : Size of transaction batches for deletions. Optional (defaults to 1).

output

• Performs a DETACH DELETE of the provided flag nodes, batched in several transactions.
• Returns the number of deleted flags.

Procedure neo4j.dq.deleteNodeFlags

Deletes all flag nodes linked to a data node.

Usage

CALL neo4j.dq.deleteNodeFlags(nodes)

parameters

• nodes (ANY: Node|[Node]|id|[ids]) : Node or list of nodes (or its/their ids) whose linked flags must be deleted.
• batchSize (Long) : Size of transaction batches for deletions. Optional (defaults to 1).

output

• Performs a DETACH DELETE of the flag nodes, batched in several transactions.
• Returns the number of deleted flags.

Procedure neo4j.dq.listFlags

Lists flag nodes.

Usage

CALL neo4j.dq.listFlags(filter)

parameters

• filter (String) : flag class for filtering results. Optional (defaults to returning all flags).

output

Returns the flag nodes.

Procedure neo4j.dq.listClasses

List DQ classes.

Usage

CALL neo4j.dq.listClasses(filter)

parameters

• filter (String) : flag class for filtering results. Optional (defaults to returning all classes).

output

Returns DQ_Class nodes.

Procedure neo4j.dq.createClass

Creates a new DQ class.

Usage

CALL neo4j.dq.createClass(class, parentClass, alertTriggerLimit, description)

parameters

• class (String) : Name of the DQ class.
• parentClass (String) : Parent DQ_Class. Optional (defaults to "all", the root of the class hierarchy).
• alertTriggerLimit (Long) : Limit above which the count of children flags should trigger an alert (Not yet implemented). Optional (defaults to -1).
• description (String) : property of the class node. Optional (defaults to "").

output

Returns the created class node.

Procedure neo4j.dq.deleteClass

Deletes a class and all its flags.

Usage

CALL neo4j.dq.deleteClass(class)

parameters

• class (String) : Name of the DQ class.

output

• Deletes all the children flags of that class.
• Any child class is kept, and re-attached to the root class.
• Deletes the class node.
• Returns the number of deleted flags.

Procedure neo4j.dq.statistics

Computes statistics about DQ flags in the graph.

Usage

CALL neo4j.dq.statistics(filter)

parameters

• filter (String) : class name for which to compute statistics.

output

Returns the counts of number of direct/indirect/total children flags for the class