14.8.3 Creating a Snapshot via ChangeSet

You can create a graph snapshot with ChangeSet via the PGX Java API. When you want to create the graph from a persistent data source, you can use PgxSession.readGraphWithProperties() with the snapshots_source configuration option set to CHANGE_SET.

You can create a snapshot via ChangeSet by performing the following steps:

1. Create a snapshot of a transient graph from database:
   • JShell
   • Java
   • Python

   opg4j> var builder = session.createGraphBuilder()
   opg4j> builder.addEdge(1, 2)
   opg4j> builder.addEdge(2, 3)
   opg4j> builder.addEdge(2, 4)
   opg4j> builder.addEdge(3, 4)
   opg4j> builder.addEdge(4, 2)
   opg4j> var graph = builder.build()

   import oracle.pgx.api.*;
   
   GraphBuilder<Integer> builder = session.createGraphBuilder();
   
   builder.addEdge(1, 2);
   builder.addEdge(2, 3);
   builder.addEdge(2, 4);
   builder.addEdge(3, 4);
   builder.addEdge(4, 2);
   
   PgxGraph graph = builder.build();

   builder = session.create_graph_builder();
   
   builder.add_edge(1, 2)
   builder.add_edge(2, 3)
   builder.add_edge(2, 4)
   builder.add_edge(3, 4)
   builder.add_edge(4, 2)
   
   graph = builder.build()

2. Create a ChangeSet from graph and populate it. The following example shows adding a new edge between vertices 1 and 4:
   • JShell
   • Java
   • Python

   opg4j> var changeSet = graph.<Integer>createChangeSet()
   opg4j> changeSet.addEdge(6, 1, 4)

   import oracle.pgx.api.*;
   GraphChangeSet<Integer> changeSet = graph.createChangeSet();
   changeSet.addEdge(6, 1, 4);

   changeSet = graph.create_change_set()changeSet.add_edge(1,4,6)

3. Create a second snapshot using GraphChangeSet.buildNewSnapshot() as shown in the following code:
   • JShell
   • Java
   • Python

   opg4j> var secondSnapshot = changeSet.buildNewSnapshot()
   opg4j> session.getAvailableSnapshots(secondSnapshot).size()
   ==> 2

   PgxGraph secondSnapshot = changeSet.buildNewSnapshot();
   System.out.println( session.getAvailableSnapshots(secondSnapshot).size() );

   second_snapshot = change_set.build_new_snapshot()
   print(len(session,get_available_snapshots()))

   Thus two snapshots, referenced via the variables graph and secondSnapshot are created.