cypher-rs

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Cypher-RS

Presentation about Cypher-RS

Neo4j server-extension that allows to configure fixed REST-Endpoints for Cypher queries.

You can PUT cypher queries to an endpoint with a certain url-suffix and then later execute those queries by running

• GET with query parameters, only readonly queries
• POST with JSON (map, list of maps) payload for parameters
• POST with CSV payload for parameters, with optional batch-size and delimiter

CREATE ENDPOINT

Verb: PUT
URL: /cypher-rs/<yourEndpoint>
Headers:
    Content-type: plain/text
Body:
    <yourCypherRequest>

Examples

PUT /cypher-rs/users
Content-type: plain/text

Body:
MATCH (n:User) WHERE n.name={name} RETURN n

--> 201 Location: /cypher-rs/users

PUT /cypher-rs/create-user
Content-type: plain/text

Body:
CREATE (n:Node {name:{name},age:{age},male:{male}})

--> 201 Location: /cypher-rs/create-user

QUERY ENDPOINT

Verb: GET
URL: /cypher-rs/<yourEndpoint>

Examples

GET /cypher-rs/users?name=Andres

--> 200
[
    {
        "name": "Andres",
        "age": 21,
        "male": true,
        "children": [
            "Cypher",
            "L.",
            "N."
        ]
    }
]

GET /cypher-rs/users?name=NotExists

--> 204

POST JSON-DATA TO ENDPOINT

Verb: POST
URL: /cypher-rs/<yourEndpoint>
Headers:
    Content-type: application/json
Body:
    <jsonData>

Examples

POST /cypher-rs/users 
Content-type: application/json

Body:
{
    "name": "Andres"
}

--> 200
[
    {
        "name": "Andres",
        "age": 21,
        "male": true,
        "children": [
            "Cypher",
            "L.",
            "N."
        ]
    }
]

POST /cypher-rs/users 
Content-type: application/json

Body: 
{
    "name": "NotExists"
}

--> 204

POST /cypher-rs/users
Content-type: application/json

Body:
[
    {
        "name": "Andres"
    },
    {
        "name": "Peter"
    },
    {
        "name": "NotExists"
    }
]

--> 200
[
    {
        "name": "Andres",
        "age": 21,
        "male": true,
        "children": [
            "Cypher",
            "L.",
            "N."
        ]
    },
    {
        "name": "Peter",
        "age": 32,
        "male": true,
        "children": [
            "Neo4j",
            "O.",
            "K."
        ]
    },
    null
]

POST CSV DATA TO ENDPOINT

Verb: POST
URL: /cypher-rs/<yourEndpoint>
Headers:
    Content-type: text/plain
Body:
    <csvData>

Examples

POST /cypher-rs/create-user
Content-type: text/plain

Body:
name,age,male\nAndres,21,true

--> 200
{
    "nodes_created": 1,
    "labels_added": 1,
    "properties_set": 3,
    "rows": 1
}

POST /cypher-rs/create-user?delim=\t&batch=20000
Content-type: text/plain

Body: name\tage\tmale\nAndres\t21\ttrue

--> 200
{
    "nodes_created": 1,
    "labels_added": 1,
    "properties_set": 3,
    "rows": 1
}

DELETE ENDPOINT

Verb: DELETE
URL: /cypher-rs/<yourEndpoint>

Example

DELETE /cypher-rs/users

--> 200 

LIST ENDPOINTS

Verb: GET
URL: /cypher-rs

Example

GET /cypher-rs

--> 200 ["users","create-user"]

GET /cypher-rs?full=true

--> 200 {"users": "start n=node:node_auto_index(name={name}) return n",
         "create-user": "create (n {name:{name},age:{age},male:{male}})"}

GET ENDPOINT QUERY

Verb: GET
URL: /cypher-rs/<yourEndpoint>/query

Example

GET /cypher-rs/users/query

--> 200 start n=node:node_auto_index(name={name}) return n

GET /cypher-rs/create-users/query

--> 200 create (n {name:{name},age:{age},male:{male}})

Types of results:

single column, single row

[
    {
        "name": "Andres",
        "age": 21,
        "male": true,
        "children": [
            "Cypher",
            "L.",
            "N."
        ]
    }
]

single column, multiple rows

[
    {
        "name": "Andres",
        "age": 21,
        "male": true,
        "children": [
            "Cypher",
            "L.",
            "N."
        ]
    },
    {
        "name": "Peter",
        "age": 32,
        "male": true,
        "children": [
            "Neo4j",
            "O.",
            "K."
        ]
    }
]

multiple columns, single row (column names are keys)

[
    {
        "user": "Andres",
        "friends": [
            "Peter",
            "Michael"
        ]
    }
]

multiple columns, multiple rows (column names are keys)

[
    {
        "user": "Andres",
        "friends": [
            "Peter",
            "Michael"
        ]
    },
    {
        "user": "Michael",
        "friends": [
            "Peter",
            "Andres"
        ]
    },
    {
        "user": "Peter",
        "friends": [
            "Andres",
            "Michael"
        ]
    }
]

Configuration

Build with mvn clean install dependency:copy-dependencies

Copy files cp target/cypher-rs-2.1-SNAPSHOT.jar target/dependency/opencsv-2.3.jar path/to/server/plugins

Add this line to path/to/server/conf/neo4j-server.properties

org.neo4j.server.thirdparty_jaxrs_classes=org.neo4j.cypher_rs=/cypher-rs

Notes

There is some magic happening with converting query parameters to cypher parameters, as query-parameters are all strings things that look like a number are converted to numbers and collections (aka multiple query parameters) are converted into lists.

Ideas

• all endpoints should be able to generate CSV when supplied with the accept header
• replace Jackson with faster Gson?
• performance tests

Concrete Example for the Movie-Graph in Neo4j-Server

A "movie and cast" endpoint

• parameter: title
• result: a document with the movie title and a collection of cast names

curl -i -XPUT -H content-type:text/plain \
 -d'MATCH (movie:Movie {title:{title}})
    OPTIONAL MATCH (movie)<-[:ACTED_IN]-(actor)
    RETURN {title:movie.title, cast: collect(actor.name)} as movie' \
 http://localhost:7474/cypher-rs/movie

// use it

curl http://localhost:7474/cypher-rs/movie?title=The%20Matrix

A "co-actors" endpoint

• parameter: name
• result: a document of the requested actor and actors who co-acted in the same movies, ordered by frequency

curl -i -XPUT -H content-type:text/plain \
 -d'MATCH (actor:Person {name:{name}})-[:ACTED_IN*2..2]-(co_actor)
    WITH actor.name as name, {name:co_actor.name, count: count(*)} as co_actors
    ORDER BY count(*) DESC
    RETURN {name:name, co_actors: collect(co_actors)} as result' \
 http://localhost:7474/cypher-rs/co-actor

// use it

curl -i http://localhost:7474/cypher-rs/co-actor?name=Keanu%20Reeves

A "create movie only" endpoint

• parameters: title and released
• result: document with the movie's properties
• uses MERGE as "get-or-create" operation

curl -i -XPUT -H content-type:text/plain \
-d'MERGE (movie:Movie {title:{title}}) ON CREATE SET movie.released={released} RETURN movie' \
 http://localhost:7474/cypher-rs/create-movie

// use it

curl -i -XPOST -H content-type:application/json -d'{"title":"Forrest Gump","released":1994}' http://localhost:7474/cypher-rs/create-movie

A "create movie with cast" endpoint

• parameters: title, released for the movies, actors for the actor names
• result: document with the movie's properties
• uses MERGE as "get-or-create" operation for both movie and actors

curl -i -XPUT -H content-type:text/plain \
-d'MERGE (movie:Movie {title:{title}}) ON CREATE SET movie.released={released}
   FOREACH (name in {actors} | MERGE (actor:Person {name:name}) MERGE (actor)-[:ACTED_IN]->(movie))
   RETURN movie' \
 http://localhost:7474/cypher-rs/create-movie2

// use it

curl -i -XPOST -H content-type:application/json -d'{"title":"Forrest Gump","released":1994, "actors":["Tom Hanks","Robin Wright","Gary Sinise"]}' http://localhost:7474/cypher-rs/create-movie2

curl http://localhost:7474/cypher-rs/movie?title=Forrest%20Gump
```