Connect 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 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 Connect in several ways:
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.
Support for Gremlin in Connect is much less complete than for Cypher. Even the parts of Gremlin that are implemented are not guaranteed to be compliant. Part of the difficulty here is that some parts of Gremlin were designed to be executed form inside a host language, most frequently Groovy, and don’t extend naturally to remote execution (see for instance this section of the Gremlin manual for some complexities around anonymous functions).