1. Graph Developer's Guide for Property Graph
  2. PGQL Property Graphs
  3. Loading a PGQL property graph into the Graph Server (PGX)
  4. Loading a PGQL Property Graph Using the readGraphByName API

10.1 Loading a PGQL Property Graph Using the readGraphByName API

You can load a PGQL property graph by name into the graph server (PGX).

You can use the PgxSession#readGraphByName API to load a PGQL property graph:

readGraphByName(String schemaName, String graphName, GraphSource source, ReadGraphOption options)

The arguments used in the method are described in the following table:

Table 10-1 Parameters for the readGraphByName method

Parameter Description Optional
schemaName Schema owner Yes
graphName Name of the PGQL property graph No
source Source format for the graph: No
options Represents the graph optimization options Yes

The readGraphByName() method reads the PGQL property graph metadata tables and internally generates the graph configuration to load the graph. You must have PGX_SESSION_NEW_GRAPH permission to use this API.

For example you can load the PGQL property graph as shown: 

opg4j> var graph = session.readGraphByName("BANKDATA", GraphSource.PG_PGQL)
$12 ==> PgxGraph[name=bankdata,N=1000,E=5001,created=1625730942294]
PgxGraph graph = session.readGraphByName("BANKDATA", GraphSource.PG_PGQL);
Graph: PgxGraph[name=bankdata,N=1000,E=5001,created=1625732149262]
>>> graph = session.read_graph_by_name('BANKDATA', 'pg_pgql')
>>> graph
PgxGraph(name: bankdata, v: 1000, e: 5001, directed: True, memory(Mb): 0)

See Also:

Mapping Oracle Database Types to PGX Types for more information on the supported types in the graph server (PGX)

Parent topic: Loading a PGQL property graph into the Graph Server (PGX)

10.1.1 Specifying Options for the readGraphByName API

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

The ReadGraphOption interface supports an additional options parameter when loading a PGQL property graph by name.

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 PGQL property graph 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 PGQL property graph for SYNCHRONIZABLE option, then ensure that the vertex and edge keys are numeric and non-composite.

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

opg4j> var graph = session.readGraphByName("BANK_GRAPH", GraphSource.PG_PGQL,
...>                            ReadGraphOption.optimizeFor(GraphOptimizedFor.READ),
...>                            ReadGraphOption.synchronizable())
graph ==> PgxGraph[name=BANK_GRAPH_2,N=1000,E=5001,created=1648457198462]

PgxGraph graph = session.readGraphByName("BANK_GRAPH", GraphSource.PG_PGQL,
                                                  ReadGraphOption.optimizeFor(GraphOptimizedFor.READ),
                                                  ReadGraphOption.synchronizable());

>>> graph = session.read_graph_by_name('BANK_GRAPH',
...      'pg_pgql', options=['optimized_for_read', '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 PGQL property graph 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. 

opg4j> session.readGraphByName("REGIONS", GraphSource.PG_PGQL,
...>                             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_PGQL, ReadGraphOption.onMissingVertex(OnMissingVertex.IGNORE_EDGE_LOG_ONCE));
>>> graph = session.read_graph_by_name('REGIONS',
...      'pg_pgql', options=['on_missing_vertex_ignore_edge_log_once'])

Parent topic: Loading a PGQL Property Graph Using the readGraphByName API

10.1.2 Specifying the Schema Name for the readGraphByName API

You can specify the schema name when using the readGraphByName API for loading a PGQL property graph.

This feature allows you to load a PGQL property graph from another user schema into the graph server (PGX). However, ensure that you have READ permission on all the underlying metadata and data tables when loading a PGQL property graph from another schema.

The following example loads a PGQL property graph from the GRAPHUSER schema: 

opg4j> var graph = session.readGraphByName("GRAPHUSER", "FRIENDS", GraphSource.PG_PGQL)
graph ==> PgxGraph[name=FRIENDS,N=6,E=4,created=1672743474212]

PgxGraph graph = session.readGraphByName("GRAPHUSER", "FRIENDS", GraphSource.PG_PGQL);

Parent topic: Loading a PGQL Property Graph Using the readGraphByName API