Supported Query Languages

thatDot Streaming Graph supports several different ways of querying the graph data. This includes some existing established query languages like Cypher and Gremlin, as well as a novel mechanism for querying future data referred to here as Standing Queries.

Cypher

Cypher is the most widely use query language for interacting with data in a property graph format. It is structurally and syntactically similar to SQL, with the main difference being the MATCH clause. The idea of MATCH is to focus on declaratively describing the graph shape (pattern) that you want and then to let the query compiler pick a good execution plan. What would normally require multiple JOIN’s in a relational model often just reduces to one MATCH with a pattern that has multiple edges:

MATCH (n: Person)-[:has_parent]->(p: Person)-[:lives_in]->(c: City)
RETURN p.name AS name, c.name AS parentsCity

Compare the above Cypher to the equivalent SQL below:

SELECT n.name AS name, c.name AS parentsCity
FROM persons AS n
JOIN persons AS p ON n.parent = p.id
JOIN cities AS c ON p.city = c.id

Cypher queries can be issued to thatDot Streaming Graph in several ways:

• entered in the query bar of the Exploration UI

• sent directly through the REST API

Gremlin

Gremlin is another graph query language, but one that is less declarative and more focused on letting users specify exactly the traversal they want. The main strength that Gremlin has is that one of its focuses is traversals: instructions for how to walk the graph structure given some starting points.

In the Exploration UI, quick queries are defined using Gremlin. This is effective because those queries often really are just about taking a couple mechanical steps away from the node on which was right clicked.