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132 lines
4.0 KiB
Markdown
132 lines
4.0 KiB
Markdown
# Neo4J
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Human Connection is a social network. Using a graph based database which can
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model nodes and edges natively - a network - feels like an obvious choice. We
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decided to use [Neo4j](https://neo4j.com/), the currently most used graph
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database available. The community edition of Neo4J is Free and Open Source and
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we try our best to keep our application compatible with the community edition
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only.
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## Installation With Docker
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Run:
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```bash
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docker-compose up
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```
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You can access Neo4J through [http://localhost:7474/](http://localhost:7474/)
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for an interactive cypher shell and a visualization of the graph.
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## Installation Without Docker
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Install the community edition of [Neo4j](https://neo4j.com/) along with the plugin
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[Apoc](https://github.com/neo4j-contrib/neo4j-apoc-procedures) on your system.
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To do so, go to [releases](https://neo4j.com/download-center/#releases), choose
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"Community Server", download the installation files for you operation system
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and unpack the files.
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Download [Neo4j Apoc](https://github.com/neo4j-contrib/neo4j-apoc-procedures/releases)
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and drop the `.jar` file into the `plugins` folder of the just extracted Neo4j-Server.
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Then make sure to allow Apoc procedures by adding the following line to your Neo4j configuration \(`conf/neo4j.conf`\):
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```
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dbms.security.procedures.unrestricted=apoc.*
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```
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### Alternatives
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You can download [Neo4j Desktop](https://neo4j.com/download/) and run locally
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for development, spin up a
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[hosted Neo4j Sandbox instance](https://neo4j.com/download/), run Neo4j in one
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of the [many cloud options](https://neo4j.com/developer/guide-cloud-deployment/),
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[spin up Neo4j in a Docker container](https://neo4j.com/developer/docker/),
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on Arch linux you can install [neo4j-community from AUR](https://aur.archlinux.org/packages/neo4j-community/)
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or on Debian-based systems install [Neo4j from the Debian Repository](http://debian.neo4j.org/).
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Just be sure to update the Neo4j connection string and credentials accordingly
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in `backend/.env`.
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Start Neo4J and confirm the database is running at [http://localhost:7474](http://localhost:7474).
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## Commands
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Here we describe some rarely used Cypher commands for Neo4j that are needed from time to time:
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### Index And Constraint Commands
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If indexes or constraints are missing or not set correctly, the browser search will not work or the database seed for development will not work.
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The indices and constraints of our database are set in `backend/src/db/migrate/store.js`.
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This is where the magic happens.
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It's called by our `prod:migrate init` command.
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This command initializes the Admin user and creates all necessary indices and constraints in the Neo4j database.
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***Calls in development***
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Locally without Docker:
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```bash
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# in backend folder
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$ yarn prod:migrate init
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```
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Locally with Docker:
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```bash
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# in main folder
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$ docker compose exec backend yarn prod:migrate init
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```
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***Calls in production***
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Locally with Docker:
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```bash
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# in main folder
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$ docker compose exec backend /bin/sh -c "yarn prod:migrate init"
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```
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On a server with Kubernetes cluster:
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```bash
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# tested for one backend replica
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# !!! be aware of the kubectl context !!!
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$ kubectl -n default exec -it $(kubectl -n default get pods | grep ocelot-backend | awk '{ print $1 }') -- /bin/sh -c "yarn prod:migrate init"
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```
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***Cypher commands to show indices and constraints***
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```bash
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# in browser command line or cypher shell
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# show all indexes and constraints
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$ :schema
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# show all indexes
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$ CALL db.indexes();
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# show all constraints
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$ CALL db.constraints();
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```
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***Cypher commands to create and drop indexes and constraints***
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```bash
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# in browser command line or cypher shell
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# create indexes
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$ CALL db.index.fulltext.createNodeIndex("post_fulltext_search",["Post"],["title", "content"]);
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$ CALL db.index.fulltext.createNodeIndex("user_fulltext_search",["User"],["name", "slug"]);
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$ CALL db.index.fulltext.createNodeIndex("tag_fulltext_search",["Tag"],["id"]);
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# drop an index
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$ DROP CONSTRAINT ON ( image:Image ) ASSERT image.url IS UNIQUE
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# drop all indexes and constraints
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$ CALL apoc.schema.assert({},{},true) YIELD label, key RETURN * ;
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```
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