Neo4J Delete or Reset Databases with examples

Today in the article, we will see how to perform Neo4J Delete or Reset Databases with examples.

Recently I had a use case where I had to delete existing corrupted data. I wanted to delete the database to allow me to remove outdated or irrelevant data to free up storage space and improve query performance.

However, you may find other use cases like the as below where you want to delete any existing database.

Example Use Cases

• Development and Testing: You might want to delete and recreate your Neo4j database to ensure a clean slate for each iteration. This helps in debugging and verifying that your data import and query processes work correctly.

• Starting Fresh: If you want to start over with a clean slate for a project, and hence you may want to delete the existing database and create a new one with the desired structure and data.

• Migrations and Upgrades: During migrations or database upgrades, you might need to delete the old database and create a new one that is compatible with the latest version of Neo4j.

• Performance Tuning: In some cases, a database may accumulate inefficiencies or performance bottlenecks over time. Deleting and recreating the database can be a way to address these issues and start with an optimized configuration.

Neo4J Delete or Reset All Databases

You may want to delete all databases in Neo4j and start with a clean slate, you can use the following steps:

Step1- Stop Neo4j Server

Before running any delete or cleanup command make sure that the Neo4j server is not running. Please use the below command to stop the neo4j server

neo4j stop

Step2- Remove the entire Graph Databases Directory

You can remove the entire Graph Databases Directory using the below command

Navigate to the Neo4j data directory, which is usually located at $NEO4J_HOME/data/databases/, and delete all the directories and files within the “databases” directory.

rm -rf data/*

OR

rm -rf $NEO4J_HOME/data/*

Note- Please identify the graph directory depending on the OS type ( Mac, Ubuntu, Windows) you are using

Step3 : Start Neo4j

neo4j start

This will remove all existing databases and start with a clean database directory.

Delete all Nodes and Relationships in Neo4j

In Neo4j, if you want to delete specific nodes in a database, you can do so by using a Cypher query to identify and delete those nodes.

Here’s how you can delete selected nodes.

Example 1

MATCH (n)
DETACH DELETE n

The above query could be causing performance issues for a large set of data.

You may use the MATCH clause to execute the query.

Example 2

MATCH (p:Person) 

WHERE p.age < 18 

DETACH DELETE p

Using DETACH DELETE remove all of the nodes and associated relationships.

If you want to delete only the nodes and keep the relationships, you can use the DELETE clause without DETACH. However, this may leave orphaned relationships.

Delete Specific Database in Neo4j

Navigate to the Neo4j data directory, which is usually located at $NEO4J_HOME/data/databases/, and delete the directory corresponding to the database you want to remove.

Example

if you want to delete a database named “testdb” you would delete the directory

 rm -rf $NEO4J_HOME/data/databases/testdb

Using Transaction – To delete All the Nodes and Relationship

BEGIN
MATCH (p:Person)
OPTIONAL MATCH (p)-[rel:RELATIONSHIP_TYPE]-()
DELETE p, rel
COMMIT

Above, please replace the Person with the actual label and “RELATIONSHIP_TYPE” with the type of relationship you want to delete.

Database Transactions are useful for data consistency and preventing issues when dealing with huge database executed with complex operations like node and relationship deletions.

That’s all! Happy coding!

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