Connecting using PGQL-on-RDBMS

To connect using DB credentials directly the following convenience method can be used, otherwise a JDBC connection object needs to be provided.

pgql.get_connection(pwd, jdbc_url)

Get a DB connection.

Parameters

  • usr – the DB user

  • pwd – the DB password

  • jdbc_url – the DB jdbc url

Returns

A PgqlConnection

Connecting to PGQL-on-RDBMS involves getting a connection object, that allows further operations such as creating a statement or retrieving metadata on the underlying JDBC connection.

class opg4py.pgql.PgqlConnection(java_pgql_connection)

Wrapper class for oracle.pg.rdbms.pgql.PgqlConnection.

clear_graph_metadata_cache()

Clear the cache that stores graph metadata.

clear_translation_cache()

Clear the cache that stores translations.

close()

Free the resources of the internal JDBC connection.

create_statement()

Creates a new PgqlStatement object, which is used to execute PGQL queries.

Returns

a new PgqlStatement object that can be used to perform PGQL queries

disable_graph_metadata_cache()

Disable the cache that stores graph metadata.

disable_translation_cache()

Disable the cache that stores translations.

enable_graph_metadata_cache()

Enable the cache that stores graph metadata.

enable_translation_cache()

Enable the cache that stores translations.

static get_connection(java_sql_connection)

Factory method to get PgqlConnection instance.

Parameters

java_sql_connection – a JDBC connection

Returns

a PgqlConnection instance

get_graph()

Get the graph name on which PGQL queries will be executed for this connection.

Returns

the graph name for this connection

get_jdbc_connection()

Get the JDBC connection that is used to execute PGQL queries.

Returns

the connection

get_schema()

Get the schema name that will be used to execute PGQL queries with this connection.

If the schema has not been set, the schema from JDBC connection is returned.

Returns

the schema set for this connection

Throws:

PgqlToSqlException - if a database access error occurs or this method is called on a closed connection

prepare_statement(pgql, timeout=0, parallel=0, dynamicSampling=2, maxResults=-1, matchOptions=None, options=None)

Creates a new PgqlPreparedStatement object, which represents a pre-compiled PGQL statement.

Parameters

  • pgql – the PGQL query to compile

  • timeout – the number of seconds for query execution to finish

  • parallel – the degree of parallelism to use for query and modify execution

  • dynamicSampling – the value for dynamic sampling

  • maxResults – the maximum number of rows returned

  • matchOptions – additional options used to influence query translation and execution

  • options – additional options used to influence modify translation and execution

Returns

a PgqlPreparedStatement object that can be used to efficiently execute the same query multiple times

set_graph(graph)

Sets the graph name on which PGQL queries will be executed for this connection.

Parameters

graph – the name of the graph

set_graph_metadata_cache_max_capacity(max_capacity)

Set max capacity value for the graph metadata cache

Parameters

max_capacity – value for max capacity

set_schema(schema)

Sets the schema name that will be used to execute PGQL queries with this connection.

Parameters

schema – the name of the schema

set_translation_cache_max_capacity(max_capacity)

Set max capacity value for the translation cache

Parameters

max_capacity – value for max capacity