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https://github.com/sim51/graphology-neo4j

Create a graphology Graph from cypher queries
https://github.com/sim51/graphology-neo4j

database graph graph-database graphology neo4j typescript

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Create a graphology Graph from cypher queries

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# Graphology Neo4j [![CI](https://github.com/sim51/graphology-neo4j/actions/workflows/test.yml/badge.svg)](https://github.com/sim51/graphology-neo4j/actions/workflows/test.yml)



Some graphology helpers for Neo4j



## Usage



This library doesn’t include the Neo4j driver library as well as the Graphology one.

They are peer dependencies, so you need to install them by yourself.



    npm install neo4j-driver graphology graphology-neo4j



### Translate a cypher query to a graph



You can create a graph directly from a cypher query.

The method `cypherToGraph` will parse the whole result to find Neo4j nodes and relationships for building the graph.



This is the definition of this method :



    /**

     * Create a graphology graph based on the result of a cypher query.

     *

     * @param neo4j Object with the neo4j's driver and optionally the database name

     * @param cypher Query to executed for the graph creation

     * @param params Query's parameters

     * @param opts Allow you to defined the graphology attribut mapping for neo4j's ids (default @id), node's labels (default @labels) & relationship's type (default @type).

     * @returns A graphology instance

     */

    export function cypherToGraph(

      neo4j: { driver: Driver; database?: string },

      cypher: string,

      params: { [param: string]: unknown } = {},

      opts: CypherToGraphOpts = { id: "@id", labels: "@labels", type: "@type" },

    ): Promise;



Example:



```typescript

import * as neo4j from "neo4j-driver";

import Graph from "graphology";

import { cypherToGraph } from "graphology-neo4j";



const driver: neo4j.Driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "admin"));

const graph: Graph = await cypherToGraph({ driver }, "MATCH (n)-[r]->(m) RETURN n,r,m");

```





Your cypher query must returned `Node`, `Relationship`, `Path`, and Arrays of those.




### Create a graph from a Cypher projection



You can create a graph from a cypher projection as defined

[here](https://neo4j.com/docs/graph-algorithms/current/projected-graph-model/cypher-projection/),

with the help of the method `cypherProjectionToGraph` .



This is the definition of this method :



    /**

     * Create a graphology graph based on the cypher projection queries.

     *

     * @param neo4j Object with the neo4j's driver and optionally the database name

     * @param cypherNodes The query to executed to get nodes. The query must return an `id` field and other fiels with be added as node's property

     * @param cypherRelationships The query to executed to get edges. The query must returns a field `source` and `target`,

     * @param params Query parameters that will be passed to both queries

     * @param opts Allow you to defined the graphology attribut mapping for neo4j's ids (default @id), node's labels (default @labels) & relationship's type (default @type).

     * @returns A graphology instance

     */

    export async function cypherProjectionToGraph(

      neo4j: { driver: Driver; database?: string },

      cypherNodes: string,

      cypherRelationships: string,

      params: { [param: string]: unknown } = {},

      opts: CypherToGraphOpts = { id: "@id", labels: "@labels", type: "@type" },

    ): Promise



Example:



```typescript

import * as neo4j from "neo4j-driver";

import Graph from "graphology";

import { cypherProjectionToGraph } from "graphology-neo4j";



const driver: neo4j.Driver = neo4j.driver("bolt://localhost", neo4j.auth.basic("neo4j", "admin"));

const graph = await cypherProjectionToGraph(

  { driver },

  "MATCH (p:Person) RETURN id(p) AS id, labels(p) AS labels, p.name AS name",

  "MATCH (p1:Person)-[:ACTED_IN]->(:Movie)<-[:ACTED_IN]-(p2:Person) WHERE id(p1) < id(p2) RETURN id(p1) AS source, id(p2) AS target, count(*) AS weight, 'COLLEAGUE' AS type",

  {},

  { id: "_id", labels: "_labels", type: "_type" },

);

```



### Export a graphology graph as a Cypher script



You can export a graph as cypher script, with the help of the method `exportToCypher`.



Example : `const cypherScript = exportToCypher(graph)`



It generates a cypher script with `CREATE` instructions.



## The graphology Graph



The graphology created graph is a multi directed graph, where self-loop are allowed (it’s like in Neo4j).

But in Graphology the notion of `label` for nodes and `type` for relationships don’t exist.

That’s why there is the `CypherToGraphOpts` object where you can define on which property those notions will be saved.



- Graphology and Neo4j id are the same, but they are also stored on nodes and edges in the property `@id`.



- Neo4j node’s labels are stored in the property `@labels`



- Neo4j edge’s type is stored in the property `@type`



## Development



To run the tests you need to have a local Neo4j server with Movie database and the password set to `admin`