Querying Databricks Data as a Graph

A step-by-step tutorial to using PuppyGraph to query data in Databricks

Summary

In this tutorial, you will:

  • Create tables in Databricks using Delta Lake format under Unity Catalog and load it with example data;

  • Start a PuppyGraph Docker container and query the example data as a graph.

Prerequisites

  • Please ensure you have a Databricks account with a workspace, catalog and SQL Warehouse set. This demo utilizes Databricks on AWS, but the setup is comparable for other platforms.

  • Accessing the PuppyGraph Web UI requires a browser.

Deployment

▶️ Run the following command to start PuppyGraph:

docker run -p 8081:8081 -p 8182:8182 -p 7687:7687 -d --name puppy --rm --pull=always puppygraph/puppygraph:stable

Data Preparation

This tutorial is designed to be comprehensive and standalone, so it includes steps to populate data in Databricks. In practical scenarios, PuppyGraph can query data directly from existing tables in your Databricks.

▶️ In your Databricks workspace: go to the SQL Editor page, select your catalog and then execute the following SQL statements in the Editor to create Delta tables with data:

create table modern.person (id string, name string, age int) USING DELTA;
insert into modern.person values
                              ('v1', 'marko', 29),
                              ('v2', 'vadas', 27),
                              ('v4', 'josh', 32),
                              ('v6', 'peter', 35);

create table modern.software (id string, name string, lang string) USING DELTA;
insert into modern.software values
                                  ('v3', 'lop', 'java'),
                                  ('v5', 'ripple', 'java');

create table modern.created (id string, from_id string, to_id string, weight double) USING DELTA;
insert into modern.created values
                               ('e9', 'v1', 'v3', 0.4),
                               ('e10', 'v4', 'v5', 1.0),
                               ('e11', 'v4', 'v3', 0.4),
                               ('e12', 'v6', 'v3', 0.2);

create table modern.knows (id string, from_id string, to_id string, weight double) USING DELTA;
insert into modern.knows values
                             ('e7', 'v1', 'v2', 0.5),
                             ('e8', 'v1', 'v4', 1.0);

The above SQL creates the following Delta tables under the modern schema:

idnameage

v1

marko

29

v2

vadas

27

v4

josh

32

v6

peter

35

Data Access Preparation

▶️ In your Databricks workspace: Goto SQL Warehouses and select Connection details tab. Save the Server hostname as it would be used later.

▶️ Log in to your Databricks workspace. Click icons on top-right, then click Settings as follows

▶️ Click on Developer tab and then click on Manage button in the Access tokens section.

▶️ Click on Generate new token and save the generated Databricks Access token for later use.

In this demo, storage parameters (Amazon S3) are also required. PuppyGraph team is going to add Credential Vending feature support soon. To learn more, please contact us.

Modeling a Graph

We then define a graph on top of the data tables we just created. Actually, this is the "Modern" graph defined by Apache Tinkerpop.

A schema instructs PuppyGraph on mapping data from the Iceberg into a graph. PuppyGraph offers various methods for schema creation. For this tutorial, we've already prepared a schema to help save time.

▶️ Create a PuppyGraph schema file schema.json with the following content. Please replace configuration parameters with the corresponding authentication information from your Databricks and AWS accounts.

schema.json
{
  "catalogs": [
    {
      "name": "delta_test",
      "type": "deltalake",
      "metastore": {
        "type": "unity",
        "host": "[databricks_host]",
        "token": "[databricks_token]",
        "databricksCatalogName": "[databricks_catalog]"
      },
      "storage": {
        "useInstanceProfile": "false",
        "region": "[s3_region]",
        "accessKey": "[s3_access_key]",
        "secretKey": "[s3_secret_key]",
        "enableSsl": "false",
        "endpoint": "",
        "enablePathStyleAccess": ""
      }
    }
  ],
  "vertices": [
    {
      "label": "person",
      "mappedTableSource": {
        "catalog": "delta_test",
        "schema": "modern",
        "table": "v_person",
        "metaFields": {
          "id": "id"
        }
      },
      "attributes": [
        {
          "type": "Int",
          "name": "age"
        },
        {
          "type": "String",
          "name": "name"
        }
      ]
    },
    {
      "label": "software",
      "mappedTableSource": {
        "catalog": "delta_test",
        "schema": "modern",
        "table": "v_software",
        "metaFields": {
          "id": "id"
        }
      },
      "attributes": [
        {
          "type": "String",
          "name": "lang"
        },
        {
          "type": "String",
          "name": "name"
        }
      ]
    }
  ],
  "edges": [
    {
      "label": "knows",
      "mappedTableSource": {
        "catalog": "delta_test",
        "schema": "modern",
        "table": "e_knows",
        "metaFields": {
          "id": "id",
          "from": "from_id",
          "to": "to_id"
        }
      },
      "from": "person",
      "to": "person",
      "attributes": [
        {
          "type": "Double",
          "name": "weight"
        }
      ]
    },
    {
      "label": "created",
      "mappedTableSource": {
        "catalog": "delta_test",
        "schema": "modern",
        "table": "e_created",
        "metaFields": {
          "id": "id",
          "from": "from_id",
          "to": "to_id"
        }
      },
      "from": "person",
      "to": "software",
      "attributes": [
        {
          "type": "Double",
          "name": "weight"
        }
      ]
    }
  ]
}

▶️ Log into PuppyGraph Web UI at http://localhost:8081 with username puppygraph and password puppygraph123.

▶️ Upload the schema by selecting the file schema.json in the Upload Graph Schema JSON block and clicking on Upload.

Once the schema is uploaded, the schema page shows the visualized graph schema as follows.

Alternative: Schema Uploading via CLI

▶️ Alternatively, run the following command to upload the schema file:

curl -XPOST -H "content-type: application/json" --data-binary @./schema.json --user "puppygraph:puppygraph123" localhost:8081/schema

The response shows that graph schema has been uploaded successfully:

{"Status":"OK","Message":"Schema uploaded and gremlin server restarted"}

Querying the Graph

In this tutorial we will use the Gremlin query language to query the Graph. Gremlin is a graph query language developed by Apache TinkerPop. Prior knowledge of Gremlin is not necessary to follow the tutorial. To learn more about it, visit https://tinkerpop.apache.org/gremlin.html.

▶️ Click on the Query panel the left side. The Gremlin Query tab offers an interactive environment for querying the graph using Gremlin.

Queries are entered on the left side, and the right side displays the graph visualization.

The first query retrieves the property of the person named "marko".

▶️ Copy the following query, paste it in the query input, and click on the run button.

g.V().has("name", "marko").valueMap()

The output is plain text like the following:

Rows: 1
age              29
name             marko

Now let's also leverage the visualization. The next query gets all the software created by people known to "marko".

▶️ Copy the following query, paste it in the query input, and click on the run button.

g.V().has("name", "marko")
  .out("knows").out("created").path()

The output is as follows. There are two paths in the result as "marko" knows "josh" who created "lop" and "ripple".

Alternative: Querying the graph via CLI

Alternatively, we can query the graph via CLI.

▶️ Execute the following command to access the PuppyGraph Gremlin Console

docker exec -it puppygraph ./bin/console

The welcome screen appears as follows:

  ____                                     ____                          _
 |  _ \   _   _   _ __    _ __    _   _   / ___|  _ __    __ _   _ __   | |__
 | |_) | | | | | | '_ \  | '_ \  | | | | | |  _  | '__|  / _` | | '_ \  | '_ \
 |  __/  | |_| | | |_) | | |_) | | |_| | | |_| | | |    | (_| | | |_) | | | | |
 |_|      \__,_| | .__/  | .__/   \__, |  \____| |_|     \__,_| | .__/  |_| |_|
                 |_|     |_|      |___/                         |_|
Welcome to PuppyGraph!
version: 0.10

puppy-gremlin>

▶️ Run the following queries in the console to query the Graph.

g.V().has("name", "marko").valueMap()

Properties of the person named "marko":

puppy-gremlin> g.V().has("name", "marko").valueMap()
Done! Elapsed time: 0.059s, rows: 1
==>map[age:29 name:marko]

▶️ To exit PuppyGraph Gremlin Console, enter the command:

:exit

Cleaning up

▶️ Run the following command to shut down and remove the services:

docker stop puppy

You can then remove the tables created in your Databricks workspace.

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