Mastering apoc.path.expand: Filtering Nodes and Links like a Pro!

Are you tired of dealing with unnecessary nodes and links in your Cypher queries? Do you want to take your graph querying skills to the next level? Look no further! In this article, we’ll dive into the powerful world of apoc.path.expand and explore the art of filtering nodes and links like a pro.

What is apoc.path.expand?

Apoc.path.expand is a powerful Cypher function provided by the APOC library, a popular graph database plugin. This function allows you to expand a pattern-based query to traverse the graph, returning a set of nodes and relationships that match the specified pattern. But, did you know that you can also use apoc.path.expand to filter out unwanted nodes and links?

Basic Syntax

apoc.path.expand(graph, startNode, 'pattern',Config)

In this syntax:

• graph is the graph database to query
• startNode is the starting node for the query
• 'pattern' is the pattern to match, such as ‘_Node’ or ‘_Relationship’
• Config is an optional configuration object to customize the query

Filtering Nodes

One of the most common use cases for apoc.path.expand is filtering nodes based on specific properties or labels. Let’s say you want to find all nodes with a specific label ‘Person’ that are within 2 hops from a start node:

MATCH (startNode:City {name: 'Paris'})
CALL apoc.path.expand(startNode, 'Person', 'Node', {
  labelFilter: 'Person',
  maxLevel: 2
}) YIELD path
RETURN path

In this example, we’re using the labelFilter configuration option to filter out nodes that don’t have the ‘Person’ label. The maxLevel option specifies the maximum depth of the traversal.

Filtering by Property

What if you want to filter nodes based on a specific property value? Let’s say you want to find all nodes with a property ‘age’ greater than 30:

MATCH (startNode:City {name: 'Paris'})
CALL apoc.path.expand(startNode, 'Person', 'Node', {
  propertyFilter: { age: 30, operator: 'gt' }
}) YIELD path
RETURN path

In this example, we’re using the propertyFilter configuration option to filter out nodes that don’t have an ‘age’ property greater than 30.

Filtering Links

But what about filtering links? Let’s say you want to find all relationships of type ‘FRIEND’ between nodes with a specific label ‘Person’:

MATCH (startNode:City {name: 'Paris'})
CALL apoc.path.expand(startNode, 'Person', 'Relationship', {
  relationshipFilter: 'FRIEND'
}) YIELD path
RETURN path

In this example, we’re using the relationshipFilter configuration option to filter out relationships that aren’t of type ‘FRIEND’.

Filtering by Property (Again!)

What if you want to filter relationships based on a specific property value? Let’s say you want to find all relationships with a property ‘since’ greater than 2010:

MATCH (startNode:City {name: 'Paris'})
CALL apoc.path.expand(startNode, 'Person', 'Relationship', {
  relationshipPropertyFilter: { since: 2010, operator: 'gt' }
}) YIELD path
RETURN path

In this example, we’re using the relationshipPropertyFilter configuration option to filter out relationships that don’t have a ‘since’ property greater than 2010.

Combining Filters

But wait, there’s more! You can combine multiple filters to create even more complex queries. Let’s say you want to find all nodes with label ‘Person’ and property ‘age’ greater than 30, and only traverse relationships of type ‘FRIEND’ with a property ‘since’ greater than 2010:

MATCH (startNode:City {name: 'Paris'})
CALL apoc.path.expand(startNode, 'Person', 'Node', {
  labelFilter: 'Person',
  propertyFilter: { age: 30, operator: 'gt' }
}, {
  relationshipFilter: 'FRIEND',
  relationshipPropertyFilter: { since: 2010, operator: 'gt' }
}) YIELD path
RETURN path

In this example, we’re using multiple filters to create a highly customized query that returns only the desired nodes and relationships.

Performance Optimization

As with any graph query, performance is crucial when working with apoc.path.expand. Here are some tips to optimize your queries:

• Use indexes on filtered properties to speed up the query
• Limit the maximum depth of the traversal using the maxLevel option
• Use the bfs (breadth-first search) option to traverse the graph more efficiently
• Use the uniqueness option to deduplicate results and reduce the amount of data returned

Conclusion

Mastering apoc.path.expand is all about understanding the power of filtering nodes and links in your Cypher queries. By combining multiple filters and optimizing your queries, you can unlock the full potential of your graph database and take your querying skills to the next level.

Remember, the key to success lies in experimenting with different filters and configurations to find the perfect combination for your specific use case. So, go ahead, get creative, and start filtering like a pro!

Filter Type	Example	Description
Label Filter	labelFilter: 'Person'	Filter nodes by label
Property Filter	propertyFilter: { age: 30, operator: 'gt' }	Filter nodes by property value
Relationship Filter	relationshipFilter: 'FRIEND'	Filter relationships by type
Relationship Property Filter	relationshipPropertyFilter: { since: 2010, operator: 'gt' }	Filter relationships by property value

Happy querying!

Frequently Asked Questions

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