gremlin-cosmos

gremlin-cosmos wraps the JavaScript implementation of gremlin to make interacting with the Gremlin API of a Cosmos DB less painful.

Install

# Install with yarn
yarn add gremlin-cosmos

# Or install with npm
npm i gremlin-cosmos

Why

Cosmos DB does not support all features of Gremlin. Most notably, it does not support Gremlin bytecode, despite that being the recommended way to use Gremlin. It also does not support the standard way to connecting to a Gremlin database, or many types of Gremlin queries.

Microsoft has documented how they intend for you to connect to, and query a Gremlin database. Because Cosmos doesn't support bytecode, you're forced you to submit Gremlin queries as strings; not a very robust solution.

This library provides:

• A strongly typed API for creating Gremlin queries
• A simplified means of connecting to a Cosmos DB's Gremlin API
• A convenient way of submitting created Gremlin queries to Cosmos

Example Usage

import {
  DbConnection,
  Query,
  GremlinResponse,
  GremlinElement,
} from 'gremlin-cosmos'

let db = new DbConnection({
  endpoint: 'wss://my-cosmos-1.gremlin.cosmos.azure.com:443',
  primaryKey: 'superSuperSecretKey==',
  database: 'my-db-1',
  collection: 'myCollection',
})

let query = Query.g.V('[e-mail]').outE('owns').inV().has('label', 'report')

try {
  await db.open()
  let response = await db.runQuery<GremlinResponse<GremlinElement>>(query)
  await db.close()
} catch (e) {
  console.error('Failed to connect to DB')
}

You'll notice that the syntax for creating a query via the Query object is very close the the syntax used with Gremlin bytecode.

DbConnection

Method signature	Description
constructor(config: DbConfig)	Instantiate a DbConnection object, but do not actually connect to the database
open(): Promise	Connect to the database
close(): Promise	Close connection to the database
runQuery<T>: Promise<T>	Run a Gremlin query against the database
use(callback: (db: DbConnection) => void): Promise<void>	A convenience method for automatically opening and closing the database connection

Query

Property name	Type	Description
g	Query	Creates a new Query object

Methods

• toString(): Get the string representation of the query.

Start Steps

• V(id?: string): Get all vertices, or the vertex with a specific id.
• E(id?: string): Get all edges, or the edge with a specific id.
• addV(label: string): Create a vertex with the specified label. Query returns the newly created vertex for adding properties.
• addE(label: string): Create an edge from the current selection with the specified label. Query returns the newly created edge for adding properties and specifying the destination vertex.

Map Steps

• count(): Count the size of the current selection.
• group(): Organizes the objects according to some function of the object. Should be followed with by().
• id(): Extracts the identifier.
• key(): Takes a property and extracts the key from it.
• label(): Takes an element and extracts the label from it.
• order(): Sort the current selection in ascending order. If the selection is made of elements, order() should be followed with by('<KEY>').
• path(): The history of the traverser is realized by examining its path.
• select(...labels: string[]): Select steps that were previously labeled with as in the traversal.
• sum(): Sums a stream of numbers.
• value(): c
• values(...keys?: string[]) - Extracts the values of properties from a selection of elements.

Vertex Steps

• out(...edgeLabels?: string[]): Move to the outgoing adjacent vertices given the edge labels.
• in(...edgeLabels?: string[]): Move to the incoming adjacent vertices given the edge labels.
• both(...edgeLabels?: string[]): Move to both the incoming and outgoing adjacent vertices given the edge labels.
• outE(...edgeLabels?: string[]): Move to the outgoing incident edges given the edge labels.
• inE(...edgeLabels?: string[]): Move to the incoming incident edges given the edge labels.
• bothE(...edgeLabels?: string[]): Move to both the incoming and outgoing incident edges given the edge labels.
• outV(): Move to the outgoing vertex.
• inV(): Move to the incoming vertex.
• bothV(): Move to both vertices.
• otherV() Move to the vertex that was not the vertex that was moved from.

Filter Steps

Filter a selection of vertices, edges, or properties to only those:

• has(key: string, value?: string): With a certain key, and optionally a certain value for that key.
• hasLabel(...labels: string[]): With one of the provided labels.
• hasId(...ids: string[]): With one of the provided ids.
• hasKey(...keys: string[]): With all of the provided keys.
• hasValue(...values: string[]): With all of the provided values.
• hasNot(key): Without a certain key.

Filter a selection of values to only those that are:

• is(eq: number): Equal to a value.
• isGt(min: number): Greater than a value.
• isLt(max: number): Less than a value.
• isGte(min: number): Greater than or equal to a value.
• isLte(max: number): Less than or equal to a value.
• isInside(min: number, max: number): Between two values.

Filter a selection of elements to:

• dedup(): Those that have not already appeared in the selection.
• range(minIndex: number, maxIndex: number): Those that lie within a particular index range of the current selection.
• limit(n: number): The first n elements.
• tail(n: number): The last n elements.

Side Effect Steps

• property(key: string, value: string): Add a property to an element.

• property(map: {[key: string]: string}): Add multiple properties to an element as specified by a JavaScript object.

• properties(key?: string): Extracts all properties from each element in the current selection. Returns a single array of all properties.

• propertyMap(): Extracts all properties from each element in the current selection as a map. Returns one map per element.

• drop(): Removes all elements and their properties in the current selection from the graph.

Step Modulators

• as(label: string): Provide a label to the step that can be accessed by later steps that make use of such labels, e.g. select(), match().

• by(key: string): If a step is able to accept traversals, functions, comparators, etc. then by() is the means by which they are added.

• from(source: string \| Query): Specify the source vertex of an edge.

• to(target: string \| Query): Specify the destination vertex of an edge.