3.3.2 Prepared PGQL Queries

You can also use prepared queries when loading a subgraph from a property graph view.

You can pass bind variables using prepared PGQL queries. The PreparedPgViewPgqlQuery#preparedPgqlQuery method adds a prepared query to a list of queries that are executed to load the subgraph. The PreparedPgViewPgqlQuery API sets the bindings for the variables and continues with the loading of the subgraph.

For example:

• JShell
• Java
• Python

opg4j> var pgViewSubgraphReader = session.readSubgraph().
...>                                      fromPgView("FRIENDS")
pgViewSubgraphReader ==> oracle.pgx.api.subgraph.PgViewSubgraphReader@33bfe6d3
opg4j> var preparedPgqlQuery = pgViewSubgraphReader.preparedPgqlQuery("MATCH (v1:Person)-[e:FriendOf]->(v2:Person) WHERE id(v2)=?")
preparedPgqlQuery ==> oracle.pgx.api.subgraph.PreparedPgViewPgqlQuery@2e6b379c
opg4j> preparedPgqlQuery = preparedPgqlQuery.withStringArg(1, "PERSONS(3)")
preparedPgqlQuery ==> oracle.pgx.api.subgraph.PreparedPgViewPgqlQuery@2e6b379c
opg4j> var graph = preparedPgqlQuery.load()
graph ==> PgxGraph[name=FRIENDS_2,N=3,E=2,created=1648566047855]

import oracle.pgx.api.subgraph.*;
…
…
PgViewSubgraphReader pgViewSubgraphReader= session.readSubgraph().fromPgView("FRIENDS");
PreparedPgViewPgqlQuery preparedPgqlQuery = pgViewSubgraphReader.preparedPgqlQuery("MATCH (v1:Person)-[e:FriendOf]->(v2:Person) WHERE id(v2)=?");
preparedPgqlQuery = preparedPgqlQuery.withStringArg(1, "PERSONS(3)"); 
PgxGraph graph = preparedPgqlQuery.load(); 

>>> from pypgx.api import PreparedPgqlQuery
>>> from pypgx.api import PreparedPgqlQueryStringArgument
>>> graph = session.read_subgraph_from_pg_view("FRIENDS",
...   [PreparedPgqlQuery("MATCH (v1:Person)-[e:FriendOf]->(v2:Person) WHERE id(v2)=?", [PreparedPgqlQueryStringArgument("PERSONS(3)")])])
>>> graph
PgxGraph(name: FRIENDS, v: 3, e: 2, directed: True, memory(Mb): 0)