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Cypher Dialect & Restrictions

DortDB's graph language is a set of implementation extensions to Cypher, based on the openCypher grammar. DortDB can parse the entire openCypher 9 grammar, but, in keeping with DortDB's data-selection focus, only the read subset is executed.

Attribution

This language is derived from the openCypher grammar and is not approved by the openCypher Implementers Group; it is best described as implementation extensions to Cypher rather than as "Cypher" or "openCypher". Cypher® is a registered trademark of Neo4j, Inc.

Supported​

  • The full openCypher 9 grammar parses.
  • Node and relationship pattern matching, in any direction.
  • Variable-length paths, e.g. -[:KNOWS *1..3]->.
  • Post-match processing: WHERE, RETURN, ORDER BY, SKIP, LIMIT, aggregation, and so on.

No data modification​

DortDB does not create or mutate data, so the data-writing clauses are rejected at planning time even though they parse:

  • CREATE, MERGE
  • SET, REMOVE
  • DELETE, DETACH DELETE

Running one of these produces an only read operations are supported error.

Standard library​

Only a subset of the standard Cypher functions and operators is currently implemented. When a function you need is missing, provide it yourself as a user-defined function or extension; this is the intended way to fill gaps in library coverage.

Custom functions for Cypher can receive a reference to the whole queried graph and its data adapter. For example, this is how the startNode function is implemented:

/** Returns the source node of an edge, or `null` when the edge is `null`. */
export const startNode: CypherFn = {
  name: 'startNode',
  addAdapterCtx: true,
  pure: true,
  impl: shortcutNulls((ctx: AdapterCtxArg, e) =>
    ctx.adapter.getEdgeNode(ctx.graph, e, 'source'),
  ),
};

Selecting the graph​

The graph a query runs against is the source named by the language's defaultGraph configuration. Alternatively, use the FROM graph clause to target a different graph.

FROM social
MATCH (p:Person)
RETURN p.name AS name