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How to query graph data in Azure Cosmos DB?
Learn how to query graph data from Azure Cosmos DB using Gremlin queries
manishmsfte
mansha
cosmos-db
apache-gremlin
tutorial
02/16/2022
mjbrown
csharp
devx-track-csharp

Tutorial: Query Azure Cosmos DB for Gremlin by using Gremlin

[!INCLUDEGremlin]

The Azure Cosmos DB API for Gremlin supports Gremlin queries. This article provides sample documents and queries to get you started. A detailed Gremlin reference is provided in the Gremlin support article.

This article covers the following tasks:

[!div class="checklist"]

  • Querying data with Gremlin

Prerequisites

For these queries to work, you must have an Azure Cosmos DB account and have graph data in the container. Don't have any of those? Complete the 5-minute quickstart to create an account and populate your database. You can run the following queries using the Gremlin console, or your favorite Gremlin driver.

Count vertices in the graph

The following snippet shows how to count the number of vertices in the graph:

g.V().count()

Filters

You can perform filters using Gremlin's has and hasLabel steps, and combine them using and, or, and not to build more complex filters. Azure Cosmos DB provides schema-agnostic indexing of all properties within your vertices and degrees for fast queries:

g.V().hasLabel('person').has('age', gt(40))

Projection

You can project certain properties in the query results using the values step:

g.V().hasLabel('person').values('name')

Find related edges and vertices

So far, we've only seen query operators that work in any database. Graphs are fast and efficient for traversal operations when you need to navigate to related edges and vertices. Let's find all friends of Thomas. We do this by using Gremlin's outE step to find all the out-edges from Thomas, then traversing to the in-vertices from those edges using Gremlin's inV step:

g.V('thomas').outE('knows').inV().hasLabel('person')

The next query performs two hops to find all of Thomas' "friends of friends", by calling outE and inV two times.

g.V('thomas').outE('knows').inV().hasLabel('person').outE('knows').inV().hasLabel('person')

You can build more complex queries and implement powerful graph traversal logic using Gremlin, including mixing filter expressions, performing looping using the loop step, and implementing conditional navigation using the choose step. Learn more about what you can do with Gremlin support!

Next steps

In this tutorial, you've done the following:

[!div class="checklist"]

  • Learned how to query using Graph

You can now proceed to the Concepts section for more information about Azure Cosmos DB.

[!div class="nextstepaction"] Global distribution