Awesome Procedures for Neo4j 5.21.x

Introduction

Neo4j 3.x introduced the concept of user-defined procedures and functions. Those are custom implementations of certain functionality, that can’t be (easily) expressed in Cypher itself. They are implemented in Java and can be easily deployed into your Neo4j instance, and then be called from Cypher directly.

As of 5.0 APOC has been split into separate repositories, one being the main, officially supported, APOC Library. The other belonging to APOC Extended. This repository handles the core part of APOC.

There are over 400 different procedures and functions in the APOC library. Their purpose is to increase functionality in areas such as data integration, graph algorithms and data conversion.

License

Apache License 2.0

"APOC" Name history

Apoc was the technician and driver on board of the Nebuchadnezzar in the Matrix movie. He was killed by Cypher.

APOC was also the first bundled A Package Of Component for Neo4j in 2009.

APOC also stands for "Awesome Procedures On Cypher"

Installation: With Neo4j Desktop

APOC can be installed with Neo4j Desktop, after creating your database, by going to the Manage screen, and then the Plugins tab. Click Install in the APOC box and wait until you see a green check mark near "APOC".

Feedback

Please provide feedback and report bugs as GitHub issues or join the Neo4j Community Forum and ask in the APOC & Procedures category.

Calling Procedures & Functions within Cypher

User defined Functions can be used in any expression or predicate, just like built-in functions.

Procedures can be called stand-alone with CALL procedure.name();

But you can also integrate them into your Cypher statements which makes them so much more powerful.

Load JSON example

WITH 'https://raw.githubusercontent.com/neo4j/apoc/5.21/core/src/test/resources/person.json' AS url

CALL apoc.load.json(url) YIELD value as person

MERGE (p:Person {name:person.name})
   ON CREATE SET p.age = person.age, p.children = size(person.children)

APOC Procedures & Functions Overview

All included procedures are listed in the overview in the documentation and detailed in subsequent sections.

Built in Help

call apoc.help('keyword')

lists name, description, signature, roles, based on keyword

Detailed Feature Documentation

See the APOC User Guide for documentation of each of the major features of the library, including data import/export, graph refactoring, data conversion, and more.

Procedure & Function Signatures

To call procedures correctly, you need to know their parameter names, types and positions. And for YIELDing their results, you have to know the output column names and types.

INFO:The signatures are shown in error messages, if you use a procedure incorrectly.

You can see the procedure’s signature in the output of CALL apoc.help("name")

CALL apoc.help("dijkstra")

The signature is always name : : TYPE, so in this case:

apoc.algo.dijkstra
 (startNode :: NODE?, endNode :: NODE?,
   relationshipTypesAndDirections :: STRING?, weightPropertyName :: STRING?)
:: (path :: PATH?, weight :: FLOAT?)

Table 1. Parameter Explanation

Name	Type
Procedure Parameters
startNode	Node
endNode	Node
relationshipTypesAndDirections	String
weightPropertyName	String
Output Return Columns
path	Path
weight	Float

Manual Installation: Download the latest release

Since APOC relies on Neo4j’s internal APIs you need to use the matching APOC version for your Neo4j installation. Make sure that the first two version numbers match between Neo4j and APOC.

Go to the latest release for the matching Neo4j version and download the binary jar to place into your $NEO4J_HOME/plugins folder.

You can find all releases here.

Manual Configuration

Warning

For security reasons, procedures and functions that use internal APIs are disabled by default. Loading and enabling APOC procedures and functions can be configured using the Neo4j config file. For more details, see the APOC installation documentation.

Version Compatibility

Since APOC relies in some places on Neo4j’s internal APIs you need to use the right APOC version for your Neo4j installation.

APOC uses a consistent versioning scheme: <neo4j-version>.<apoc> version. The trailing <apoc> part of the version number will be incremented with every apoc release.

One should always use the highest patch APOC version available for the related Neo4j Version.

For example: When using Neo4j 5.4.0, the corresponding APOC version will be 5.4.x, where x is the highest patch version released. In this case, if an APOC 5.4.0 and 5.4.1 version exist, one should use APOC 5.4.1. If a Neo4j 5.4.2 version existed, it is still okay to use APOC 5.4.1, as only the first 2 numbers need to match.

For 4.4.x releases of APOC, all releases are found here.

Get APOC Version

To know your current apoc version you can use the function :

RETURN apoc.version();

Using APOC with the Neo4j Docker image

APOC can be used with the Neo4j Docker image via the NEO4J_PLUGINS environment variable. If we use this environment variable, the APOC plugin will be copied from the Docker image and configured at runtime.

Note	This feature is intended to facilitate using APOC in development environments, but it is not recommended for use in production environments.

The following runs Neo4j 5.21.0 in a Docker container with the latest version of the APOC Library

docker run \
    -p 7474:7474 -p 7687:7687 \
    --name neo4j-apoc \
    -e NEO4J_apoc_export_file_enabled=true \
    -e NEO4J_apoc_import_file_enabled=true \
    -e NEO4J_apoc_import_file_use__neo4j__config=true \
    -e NEO4J_PLUGINS=\[\"apoc\"\] \
    neo4j:5.21.0

We should see the following line in the output after running this command:

Installing Plugin 'apoc' from /var/lib/neo4j/labs/apoc-*-core.jar to /var/lib/neo4j/plugins/apoc.jar

In a production environment we should download the latest APOC release matching our Neo4j version, and copy it to a local folder. Supplying it as a data volume mounted at /plugins.

The following downloads the APOC Library into the plugins directory and then mounts that folder to the Neo4j Docker container

mkdir plugins
pushd plugins
wget https://github.com/neo4j/apoc/releases/download/5.21.0/apoc-5.21.0-core.jar
popd
docker run --rm -e NEO4J_AUTH=none -p 7474:7474 -v $PWD/plugins:/plugins -p 7687:7687 neo4j:5.21.0

If you want to pass custom APOC config to your Docker instance, you can use environment variables, like here:

docker run \
    -p 7474:7474 -p 7687:7687 \
    -v $PWD/data:/data -v $PWD/plugins:/plugins \
    --name neo4j-apoc \
    -e apoc.export.file.enabled=true \
    -e apoc.import.file.enabled=true \
    -e apoc.import.file.use_neo4j_config=true \
    neo4j:5.21.0

To then use Neo4j with Docker, it is possible to run the Cypher-shell like so:

docker exec -it neo4j-apoc bin/cypher-shell

Build & install the current development branch from source

git clone https://github.com/neo4j/apoc
cd apoc
./gradlew shadow
cp build/extended/libs/apoc-<version>.jar $NEO4J_HOME/plugins/
$NEO4J_HOME/bin/neo4j restart

A full build including running the tests can be run by ./gradlew build.

You can either copy the jar (build/libs) into the neo4j target folder (target/neo4j/plugins folder) or launch it in a dockerized neo4j by mounting the directory containing the apoc-procedures jar as a volume.

Running APOC tests

With intellij - right-click on the test folder, and you will be able to run all tests from there With gradle - ./gradlew test

Or as normal, click the play button on the test you would like to run. === Applying Code-style

./gradlew spotlessApply

To apply the spotless code-style, run the above gradle command, this will remove all unused imports