3.1.1 Specifying Options for readGraphByName API

You can specify graph optimization options, OnMissingVertexOption or both when using the readGraphByName API for loading a property graph view.

The ReadGraphOption interface supports an additional options parameter when loading a property graph view by name:

readGraphByName(String name, GraphSource source, ReadGraphOption options)

The following sections explain the various options supported by the ReadGraphOption interface.

Using the Graph Optimization Options

You can optimize the read or update performance when loading a property graph view by name by using one of the following options:

• ReadGraphOption.optimizeFor(GraphOptimizedFor.READ): Specifies that the loaded graph is optimized for READ.
• ReadGraphOption.optimizeFor(GraphOptimizedFor.UPDATES): Specifies that the loaded graph is optimized for UPDATE.
• ReadGraphOption.synchronizable(): Specifies that the loaded graph can be synchronized.

It is important to note the following:

• synchronizable() option can be used in combination with UPDATE and READ. However, the UPDATE and READ options cannot be used at the same time.
• If you are loading a property graph view for SYNCHRONIZABLE option, then ensure that the vertex and edge keys are numeric and non-composite.

The following example loads a property graph view for READ and SYNCHRONIZABLE options:

• JShell
• Java

opg4j> var graph = session.readGraphByName("BANK_GRAPH_VIEW", GraphSource.PG_VIEW,
...>                            ReadGraphOption.optimizeFor(GraphOptimizedFor.READ),
...>                            ReadGraphOption.synchronizable())
graph ==> PgxGraph[name=BANK_GRAPH_VIEW_2,N=1000,E=5001,created=1648457198462]

PgxGraph graph = session.readGraphByName("BANKDATAVIEW", GraphSource.PG_VIEW, "BANK_GRAPH_VIEW", GraphSource.PG_VIEW,
                                                  ReadGraphOption.optimizeFor(GraphOptimizedFor.READ),
                                                  ReadGraphOption.synchronizable());

Using the OnMissingVertex Options

If either the source or destination vertex or both are missing for an edge, then you can use the OnMissingVertexOption which specifies the behavior for handling the edge with the missing vertex. The following values are supported for this option:

• ReadGraphOption.onMissingVertex(OnMissingVertex.ERROR): This is the default option and this specifies that an error must be thrown for edges with missing vertices.
• ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE): Specifies that the edge for a missing vertex must be ignored.
• ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE_LOG): Specifies that the edge for a missing vertex must be ignored and all ignored edges must be logged.
• ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE_LOG_ONCE): Specifies that the edge for a missing vertex must be ignored and only the first ignored edge must be logged.

The following example loads the property graph view by ignoring the edges with missing vertices and logging only the first ignored edge. Note, to view the logs, you must update the default Logback configuration file in /etc/oracle/graph/logback.xml and the graph server (PGX) logger configuration file in /etc/oracle/graph/logback-server.xml to log the DEBUG logs. You can then view the ignored edges in /var/opt/log/pgx-server.log file.

• JShell
• Java

opg4j> session.readGraphByName("REGIONS", GraphSource.PG_VIEW,
...>                             ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE_LOG_ONCE))
$7 ==> PgxGraph[name=REGIONVIEW_3,N=27,E=18,created=1655903219910]

PgxGraph graph = session.readGraphByName("REGIONS", GraphSource.PG_VIEW, ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE_LOG_ONCE));