Patterns

Graph pattern matching sits at the very core of Cypher®. It is the mechanism used to navigate, describe and extract data from a graph by applying a declarative pattern. Inside a MATCH clause, you specify graph patterns to search for, and return the paths that match them. Graph pattern matching can also be used without a MATCH clause, in the subqueries EXISTS, COUNT, and COLLECT.

A graph pattern describes data using a syntax that is similar to how the nodes and relationships of a property graph are drawn on a whiteboard. On a whiteboard, nodes are drawn as circles and relationships are drawn as arrows. Cypher represents the circles as a pair of parentheses, and the arrows as dashes and greater-than or less-than symbols:

These simple patterns for nodes and relationships form the building blocks of path patterns that can match paths of a fixed length. As well as discussing simple fixed-length patterns, this chapter covers more complex patterns, showing how to match patterns of a variable or unknown length, find the shortest paths between a given set of nodes, add inline filters for improved query performance, and add cycles and non-linear shapes to path patterns. It also discusses Cypher’s default behavior of not allowing relationships to be traversed in a match pattern, and how to alter this default, either by allowing the re-traversal of relationships using REPEATABLE ELEMENTS or by disallowing nodes to be repeated in a path with the ACYCLIC keyword.

This chapter includes the following sections:

The model data in the examples used in this chapter are based on the UK national rail network, using publicly available datasets.