PGQL: a Property Graph Query Language

PGQL is a SQL-like query language for the Property Graph data model. See PGQL Home and PGQL 1.0 Specification.

This reposistory contains:

• The specification of PGQL
• A parser for PGQL that provides various static error checks to validate queries
• An intermediate representation of graph queries (see GraphQuery.java)
  • GraphQuery objects are returned by the parser and they can be used as a starting point when implementing a graph query engine
• PGQL compatibility tests (in-progress)

Build and Install

PGQL can be built on Windows, Linux and Mac OS X and requires Java 1.8 or higher and Maven 3.3.9 or higher.

On Linux / Mac OS X:

• To build and install to your local Maven repository, run sh install.sh

You can easily adapt the scripts to work with Windows.

Getting Started

First, build and install PGQL like explained above. Then, execute cd example; sh run.sh to parse two example queries:

public class Main {

  public static void main(String[] args) throws PgqlException {

    Pgql pgql = new Pgql();

    // parse query and print graph query
    PgqlResult result1 = pgql.parse("SELECT n WHERE (n) -[e]-> (m)");
    System.out.println(result1.getGraphQuery());

    // parse query with errors and print error messages
    PgqlResult result2 = pgql.parse("SELECT x, y, WHERE (n) -[e]-> (m)");
    System.out.println(result2.getErrorMessages());
  }
}

The AST returned by the parser is a GraphQuery object. This would be the input to your query planner.

Documentation

See PGQL 1.0 Specification.

Development

• Download Eclipse with Spoofax 2.1.0 pre-installed here
• Import the following projects into Eclipse (File>Import...>Maven>Existing Maven Projects>Browse...):
  • graph-query-ir: Java representation of graph queries
  • pqgl-spoofax: Spoofax implementation of PGQL (parser + error checks)
  • pgql-lang: translation of Spoofax AST into graph-query-ir

Contributions

PGQL is an open source project. See Contributing for details.

Oracle gratefully acknowledges the contributions to PGQL made by the community.