Welcome to OPG4Py 21.4.0 documentation!¶

Example application¶

Create a python app python_app.py with the following content:

import sys

jdbc_url = sys.argv[1]
base_url = sys.argv[2]
username = sys.argv[3]
password = sys.argv[4]


# 2 tier example: run PGQL against database
import opg4py

pgql_connection = opg4py.pgql.get_connection(username, password, jdbc_url)
pgql_statement = pgql_connection.create_statement()

create_graph = "CREATE PROPERTY GRAPH hr_simplified VERTEX TABLES (employees LABEL employee PROPERTIES ARE ALL COLUMNS EXCEPT ( job_id, manager_id, department_id ), departments LABEL department PROPERTIES ( department_id, department_name )) EDGE TABLES ( employees AS works_for SOURCE KEY ( employee_id ) REFERENCES employees DESTINATION employees NO PROPERTIES)"

pgql_statement.execute(create_graph)
pgql_connection.set_graph("hr_simplified")

query = "SELECT label(n) AS srcLbl, label(e) AS edgeLbl, label(m) AS dstLbl, COUNT(*) FROM MATCH (n) -[e]-> (m) GROUP BY srcLbl, edgeLbl, dstLbl ORDER BY COUNT(*) DESC"

pgql_result_set = pgql_statement.execute_query(query)
pgql_result_set.print()
drop_graph = "DROP PROPERTY GRAPH hr_simplified"
pgql_statement.execute(drop_graph)

pgql_result_set.close()
pgql_statement.close()
pgql_connection.close()


# 3-tier example: connect to PGX
import pypgx as pgx
import pypgx.pg.rdbms.graph_server as graph_server

instance = graph_server.get_instance(base_url, username, password)
session = instance.create_session("pypgx_example_session")
graph = session.create_graph_builder().add_edge(1, 2).add_edge(2, 3).add_edge(3, 1).build()
analyst = session.create_analyst()

triangles = analyst.count_triangles(graph, True)
print("triangles = {}".format(triangles))

rs = graph.query_pgql("select x, y, e from match (x) -[e]-> (y)")
rs.print()

session.close()

Start the Graph Server¶

Configure and start the graph server to which the example application can connect to. Follow the steps in the product documentation.

Test the application¶

Test the app using the following instruction, replacing <connect-string>, <hostname>, <username> and <password> with values matching your database and graph server installation:

python3 python_app.py "<connect-string>" "https://<hostname>:7007" "<username>" "<password>"

You should see an output like this:

+--------------------------------------------+
| SRCLBL   | EDGELBL   | DSTLBL   | COUNT(*) |
+--------------------------------------------+
| EMPLOYEE | WORKS_FOR | EMPLOYEE | 106      |
+--------------------------------------------+

triangles = 1

+---------------------------------------------------+
| x               | y               | e             |
+---------------------------------------------------+
| PgxVertex[ID=1] | PgxVertex[ID=2] | PgxEdge[ID=0] |
| PgxVertex[ID=2] | PgxVertex[ID=3] | PgxEdge[ID=1] |
| PgxVertex[ID=3] | PgxVertex[ID=1] | PgxEdge[ID=2] |
+---------------------------------------------------+