15.7.3 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:
   Creating a Graph Snapshot Using JShell

   opg4j> String statement = 
   ...>   "CREATE PROPERTY GRAPH bank_graph "
   ...> + "VERTEX TABLES ( BANK_NODES as ACCOUNTS "
   ...> + "KEY (ID) "
   ...> + "LABEL ACCOUNTS "
   ...> + "PROPERTIES (ID, LABEL) "
   ...> + ") "
   ...> + "EDGE TABLES ( BANK_EDGES_AMT "
   ...> + "KEY (SRC_ID, DEST_ID, AMOUNT) "
   ...> + "SOURCE KEY (SRC_ID) REFERENCES ACCOUNTS "
   ...> + "DESTINATION KEY (DEST_ID) REFERENCES ACCOUNTS "
   ...> + "LABEL TRANSFERS "
   ...> + "PROPERTIES (SRC_ID, DEST_ID, AMOUNT, LABEL) "
   ...> + ") ";
   statement ==> "CREATE PROPERTY GRAPH bank_graph VERTEX TABLES ( BANK_NODES as ACCOUNTS KEY (ID) LABEL ACCOUNTS PROPERTIES (ID, LABEL) ) EDGE TABLES ( BANK_EDGES_AMT KEY (SRC_ID, DEST_ID, AMOUNT) SOURCE KEY (SRC_ID) REFERENCES ACCOUNTS DESTINATION KEY (DEST_ID) REFERENCES ACCOUNTS LABEL TRANSFERS PROPERTIES (SRC_ID, DEST_ID, AMOUNT, LABEL) ) "
   opg4j> session.executePgql(statement);
   opg4j> session.getGraph("bank_graph");
   

   Creating a Graph Snapshot Using Java

   import oracle.pgx.api.*;
   pgqlStmt = pgqlConn.createStatement();
   String pgql = "CREATE PROPERTY GRAPH " + bank_graph + " "+
   "VERTEX TABLES ( BANK_NODES as ACCOUNTS " +
   "KEY (ID) " +
   "LABEL ACCOUNTS " +
   "PROPERTIES (ID, LABEL) " +
   ") " +
   "EDGE TABLES ( BANK_EDGES_AMT " +
   "KEY (SRC_ID, DEST_ID, AMOUNT) " +
   "SOURCE KEY (SRC_ID) REFERENCES ACCOUNTS " +
   "DESTINATION KEY (DEST_ID) REFERENCES ACCOUNTS " +
   "LABEL TRANSFERS " +
   "PROPERTIES (SRC_ID, DEST_ID, AMOUNT, LABEL) " +
   ")";
   pgqlStmt.execute(pgql);

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

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

   Creating a ChangeSet Using Java

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

   Creating a ChangeSet Using Python

   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:
   Creating a ChangeSet with GraphChangeSet API Using JShell

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

   Creating a ChangeSet with GraphChangeSet API Using Java

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

   Creating a ChangeSet with GraphChangeSet API Using Python

   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.