An Introduction to APOC in Neo4j

APOC:-

Awesome Procedures on cypher. It's a package of components for Neo4j database. It's a library of procedures in Neo4j.
 

Areas of APOC:-

Here are some areas from where it contains procedures are

• Graph Algorithm
• Metadata
• Manual Indexes and relationship indexes
• Integrated with other databases like Cassandra,MongoDB and  relation databases
• Import and export
• Date and Time functions
• XML loading and JSON loading from Apis and files.
• String and text functions
• Support data as Json or HashMap in a Node.

Steps to Use APOC:-

1. Download the latest binary jar from https://github.com/neo4j-contrib/neo4j-apoc-procedures/releases/3.2.0.4
2. put this jar into your plugins folder inside Neo4j
3. Restart Neo4j.

 After restarting your server you will see a lot of procedures.

to check all procedures  hit the following Query.

     dbms.procedures();

for help  in APOC use following Query

     apoc.help("apoc");

Loading data from Web and Other APIs:-

With the help of APOC you can load the data from web url and APis.

In data If the result is a JSON object, then it will be returned as a singular map. and  if it is an array, then  it will be turned into a stream of maps. 

Suppose that we want to load data from any URL then we have to use following query to load data into our neo4j database.

     
WITH "Your Specified URL" AS url
CALL apoc.load.json(url) YIELD value
UNWIND value.items AS item
RETURN item.title, item.owner, item.creation_date, keys(item)

We will cover more on this in next part

Creating Map:-

Currently, you can't create a map from raw data in  Cypher, only properties  are supported. but with the help of apoc we can do this.

to create a map from pairs of data you have to use following query in neo4J

     WITH [["Fruit","Apple"],["Vegetable","Ladyfinger"],["Sports","Cricket"],
      ["Animal","Loin"]] as pairs
CALL apoc.map.fromPairs(pairs) YIELD value as map
RETURN map

OutPut of the following query:-

    map
    {Fruit:"Apple", Vegetable:"Vegetable", Sports:"Cricket", Animal:"Loin"}

Creating Dynamic Keys in map:-

By simply using cypher we can't add dynamic keys in map in neo4j

Let's take an example

If We will execute this query without using apoc it will not add dynamic key 

       WITH "a" as dynamicKey, "b" as dynamicValue
       RETURN { dynamicKey: dynamicValue } AS map

Output

            map            
{"dynamicKey":"b"}

But, If we use apoc then it will add dynamic key as "a":"b"

Query to add dynamic keys 

       WITH "a" as dynamicKey, "b" as dynamicValue
      RETURN apoc.map.fromValues([dynamicKey, dynamicValue]) AS map

Output:-
      map
 {"a":"b"}
 

Usage of APOC in Date/Time:-

apoc is also used in date time conversion.

to parse the date we have to use following query

     apoc.date.parse('2015/03/25 03:15:59',['ms'/'s'], ['yyyy/MM/dd HH:mm:ss'])

To get  the system timezone display format string we have to use following query using apoc.

     apoc.date.systemTimezone()

Thanks