https://github.com/prillan/eta-neo4j-example

https://github.com/prillan/eta-neo4j-example

Last synced: 15 days ago
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• Host: GitHub
• URL: https://github.com/prillan/eta-neo4j-example
• Owner: Prillan
• Created: 2017-01-15T17:07:16.000Z (almost 8 years ago)
• Default Branch: master
• Last Pushed: 2017-01-16T19:46:15.000Z (almost 8 years ago)
• Last Synced: 2024-10-28T00:21:27.300Z (2 months ago)
• Language: Java
• Size: 11.7 KB
• Stars: 4
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.md

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README

        
# Eta (Haskell) and Neo4j

This is a repository combining examples from the neo4j website on

stored procedures and user functions and from the Eta website on how

to export Java functions written in Eta (Haskell).

## Setup

To get things going you need `eta` ([installation instructions](http://eta-lang.org/docs/html/getting-started.html#installating-eta)),

`neo4j` ([website](https://neo4j.com)), Java 8 and `maven`.

Make sure you set `JAVA_HOME` to your Java 8 directory in

`wrapper/build.sh`.

Run `build.sh`.

If everything goes well it produces `output.jar` in the root directory

of this repository. Copy that file to neo4j's `plugins` directory, for

me that is `/var/lib/neo4j/plugins`. Restart `neo4j` and try out the

example function `fib`.

```shell

neo4j-sh (?)$ return example.fib(12);

+-----------------+

| example.fib(12) |

+-----------------+

| 233             |

+-----------------+

1 row

55 ms

```

## Gotchas

- Eta currently does not support annotations, so we need a Java

  wrapper library.

- Make sure the Eta project is compiled as an executable, otherwise

  the Eta runtime won't be included and execution of the user function

  will fail with `Failed to invoke function 'example.fib': Caused by:

  java.lang.NoClassDefFoundError: eta/runtime/stg/StgClosure`.

- Use a very simple local maven repository to store the produced `jar`

  file, this makes sure that it's included in the next `jar` file that

  gets included by neo4j.