15. API: AsyncConnection Objects

An AsyncConnection object can be created with oracledb.connect_async() or with AsyncConnectionPool.acquire(). AsyncConnections support use of concurrent programming with asyncio. Unless explicitly noted as synchronous, the AsyncConnection methods should be used with await. This object is an extension to the DB API.

Added in version 2.0.0.

Note

AsyncConnection objects are only supported in the python-oracledb Thin mode.

Note

Any outstanding database transaction will be rolled back when the connection object is destroyed or closed. You must perform a commit first if you want data to persist in the database, see Managing Transactions Using Asynchronous Methods.

15.1. AsyncConnection Methods

AsyncConnection.__aenter__(): The entry point for the asynchronous connection as a context manager. It returns itself.

AsyncConnection.__aexit__(): The exit point for the asynchronous connection as a context manager. This will close the connection and roll back any uncommitted transaction.

AsyncConnection.callfunc(name, return_type, parameters=[], keyword_parameters={})

Calls a PL/SQL function with the given name.

This is a shortcut for creating a cursor, calling the stored function with the cursor, and then closing the cursor.

AsyncConnection.callproc(name, parameters=[], keyword_parameters={})

Calls a PL/SQL procedure with the given name.

This is a shortcut for creating a cursor, calling the stored procedure with the cursor, and then closing the cursor.

AsyncConnection.cancel(): A synchronous method that breaks a long-running statement.

AsyncConnection.changepassword(old_password, new_password): Changes the password for the user to which the connection is connected.

AsyncConnection.close(): Closes the connection.

AsyncConnection.commit(): Commits any pending transaction to the database.

AsyncConnection.createlob(lob_type): Creates and returns a new temporary LOB of the specified type.

AsyncConnection.cursor(scrollable=False): A synchronous method that returns a cursor associated with the connection.

AsyncConnection.decode_oson(data): A synchronous method that decodes OSON-encoded bytes and returns the object encoded in those bytes. This is useful for fetching columns which have the check constraint IS JSON FORMAT OSON enabled.

Added in version 2.1.0.

AsyncConnection.encode_oson(value): A synchronous method that encodes a Python value into OSON-encoded bytes and returns them. This is useful for inserting into columns which have the check constraint IS JSON FORMAT OSON enabled.

Added in version 2.1.0.

AsyncConnection.execute(statement, parameters=[])

Executes a statement against the database.

This is a shortcut for creating a cursor, executing a statement with the cursor, and then closing the cursor.

AsyncConnection.executemany(statement, parameters=[])

Prepares a statement for execution against a database and then executes it against all parameter mappings or sequences found in the sequence parameters.

This is a shortcut for creating a cursor, calling AsyncCursor.executemany() on the cursor, and then closing the cursor.

AsyncConnection.fetchall(statement, parameters=None, arraysize=None, rowfactory=None): Executes a query and returns all of the rows. After the rows are fetched, the cursor is closed.

AsyncConnection.fetchmany(statement, parameters=None, num_rows=None, rowfactory=None): Executes a query and returns up to the specified number of rows. After the rows are fetched, the cursor is closed.

AsyncConnection.fetchone(statement, parameters=None, rowfactory=None): Executes a query and returns the first row of the result set if one exists (or None if no rows exist). After the row is fetched, the cursor is closed.

AsyncConnection.gettype(name): Returns a type object given its name. This can then be used to create objects which can be bound to cursors created by this connection.

AsyncConnection.is_healthy()

A synchronous method that returns a boolean indicating the health status of a connection.

Connections may become unusable in several cases, such as, if the network socket is broken, if an Oracle error indicates the connection is unusable, or, after receiving a planned down notification from the database.

This function is best used before starting a new database request on an existing standalone connection. Pooled connections internally perform this check before returning a connection to the application.

If this function returns False, the connection should be not be used by the application and a new connection should be established instead.

This function performs a local check. To fully check a connection’s health, use AsyncConnection.ping() which performs a round-trip to the database.

AsyncConnection.ping(): Pings the database to verify if the connection is valid.

AsyncConnection.rollback(): Rolls back any pending transaction.

AsyncConnection.tpc_begin(xid, flags, timeout)

Begins a Two-Phase Commit (TPC) on a global transaction using the specified transaction identifier (xid).

The xid parameter should be an object returned by the xid() method.

The flags parameter is one of the constants oracledb.TPC_BEGIN_JOIN, oracledb.TPC_BEGIN_NEW, oracledb.TPC_BEGIN_PROMOTE, or oracledb.TPC_BEGIN_RESUME. The default is oracledb.TPC_BEGIN_NEW.

The timeout parameter is the number of seconds to wait for a transaction to become available for resumption when TPC_BEGIN_RESUME is specified in the flags parameter. When TPC_BEGIN_NEW is specified in the flags parameter, the timeout parameter indicates the number of seconds the transaction can be inactive before it is automatically terminated by the system. A transaction is inactive between the time it is detached with AsyncConnection.tpc_end() and the time it is resumed with AsyncConnection.tpc_begin().The default is 0 seconds.

The following code sample demonstrates the tpc_begin() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_begin(xid=x, flags=oracledb.TPC_BEGIN_NEW, timeout=30)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_commit(xid, one_phase)

Commits a global transaction. When called with no arguments, this method commits a transaction previously prepared with tpc_begin() and optionally prepared with tpc_prepare(). If tpc_prepare() is not called, a single phase commit is performed. A transaction manager may choose to do this if only a single resource is participating in the global transaction.

If an xid parameter is passed, then an object should be returned by the xid() function. This form should be called outside of a transaction and is intended for use in recovery.

The one_phase parameter is a boolean identifying whether to perform a one-phase or two-phase commit. If one_phase parameter is True, a single-phase commit is performed. The default value is False. This parameter is only examined if a value is provided for the xid parameter. Otherwise, the driver already knows whether tpc_prepare() was called for the transaction and whether a one-phase or two-phase commit is required.

The following code sample demonstrates the tpc_commit() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_commit(xid=x, one_phase=False)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_end(xid, flags)

Ends or suspends work on a global transaction. This function is only intended for use by transaction managers.

If an xid parameter is passed, then an object should be returned by the xid() function. If no xid parameter is passed, then the transaction identifier used by the previous tpc_begin() is used.

The flags parameter is one of the constants oracledb.TPC_END_NORMAL or oracledb.TPC_END_SUSPEND. The default is oracledb.TPC_END_NORMAL.

If the flag is oracledb.TPC_END_SUSPEND then the transaction may be resumed later by calling AsyncConnection.tpc_begin() with the flag oracledb.TPC_BEGIN_RESUME.

The following code sample demonstrates the tpc_end() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_end(xid=x, flags=oracledb.TPC_END_NORMAL)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_forget(xid)

Causes the database to forget a heuristically completed TPC transaction. This function is only intended to be called by transaction managers.

The xid parameter is mandatory and should be an object should be returned by the xid() function.

The following code sample demonstrates the tpc_forget() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_forget(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_prepare(xid)

Prepares a two-phase transaction for commit. After this function is called, no further activity should take place on this connection until either tpc_commit() or tpc_rollback() have been called.

Returns a boolean indicating whether a commit is needed or not. If you attempt to commit when not needed, then it results in the error ORA-24756: transaction does not exist.

If an xid parameter is passed, then an object should be returned by the xid() function. If an xid parameter is not passed, then the transaction identifier used by the previous tpc_begin() is used.

The following code sample demonstrates the tpc_prepare() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_prepare(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_recover()

Returns a list of pending transaction identifiers that require recovery. Objects of type Xid (as returned by the xid() function) are returned and these can be passed to tpc_commit() or tpc_rollback() as needed.

This function queries the view DBA_PENDING_TRANSACTIONS and requires SELECT privilege on that view.

The following code sample demonstrates the tpc_recover() function:

await connection.tpc_recover()

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

AsyncConnection.tpc_rollback(xid)

Rolls back a global transaction.

If an xid parameter is not passed, then it rolls back the transaction that was previously started with tpc_begin().

If an xid parameter is passed, then an object should be returned by xid() and the specified transaction is rolled back. This form should be called outside of a transaction and is intended for use in recovery.

The following code sample demonstrates the tpc_rollback() function:

x = connection.xid(format_id=1, global_transaction_id="tx1", branch_qualifier="br1")
await connection.tpc_rollback(xid=x)

See Using Two-Phase Commits (TPC) for information on TPC.

Added in version 2.3.0.

15.2. AsyncConnection Attributes

AsyncConnection.action: This write-only attribute sets the action column in the v$session table. It is a string attribute but the value None is accepted and treated as an empty string.

AsyncConnection.autocommit: This read-write attribute determines whether autocommit mode is on or off. When autocommit mode is on, all statements are committed as soon as they have completed executing.

AsyncConnection.call_timeout

This read-write attribute specifies the amount of time (in milliseconds) that a single round-trip to the database may take before a timeout will occur. A value of 0 means that no timeout will take place.

If a timeout occurs, the error DPI-1067 will be returned if the connection is still usable. Alternatively the error DPI-1080 will be returned if the connection has become invalid and can no longer be used.

AsyncConnection.client_identifier: This write-only attribute sets the client_identifier column in the v$session table.

AsyncConnection.clientinfo: This write-only attribute sets the client_info column in the v$session table.

AsyncConnection.current_schema: This read-write attribute sets the current schema attribute for the session. Setting this value is the same as executing the SQL statement ALTER SESSION SET CURRENT_SCHEMA. The attribute is set (and verified) on the next call that does a round trip to the server. The value is placed before unqualified database objects in SQL statements you then execute.

AsyncConnection.db_domain: This read-only attribute specifies the Oracle Database domain name associated with the connection. It is the same value returned by the SQL SELECT value FROM V$PARAMETER WHERE NAME = 'db_domain'.

AsyncConnection.db_name: This read-only attribute specifies the Oracle Database name associated with the connection. It is the same value returned by the SQL SELECT NAME FROM V$DATABASE.

AsyncConnection.dbop: This write-only attribute sets the database operation that is to be monitored. This can be viewed in the DBOP_NAME column of the v$sql_monitor table.

AsyncConnection.dsn: This read-only attribute returns the TNS entry of the database to which a connection has been established.

AsyncConnection.econtext_id: This write-only attribute specifies the execution context id. This value can be found as ecid in the v$session table and econtext_id in the auditing tables. The maximum length is 64 bytes.

AsyncConnection.edition: This read-only attribute gets the session edition and is only available in Oracle Database 11.2 (the server must be at this level or higher for this to work). This attribute is ignored in python-oracledb Thin mode.

AsyncConnection.external_name: This read-write attribute specifies the external name that is used by the connection when logging distributed transactions.

AsyncConnection.inputtypehandler: This read-write attribute specifies a method called for each value that is bound to a statement executed on any cursor associated with this connection. The method signature is handler(cursor, value, arraysize) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, the default behavior will take place for all values bound to statements.

AsyncConnection.instance_name: This read-only attribute specifies the Oracle Database instance name associated with the connection. It is the same value as the SQL expression sys_context('userenv', 'instance_name').

AsyncConnection.internal_name: This read-write attribute specifies the internal name that is used by the connection when logging distributed transactions.

AsyncConnection.ltxid: This read-only attribute returns the logical transaction id for the connection. It is used within Oracle Transaction Guard as a means of ensuring that transactions are not duplicated. See the Oracle documentation and the provided sample for more information.

AsyncConnection.max_open_cursors: This read-only attribute specifies the maximum number of cursors that the database can have open concurrently. It is the same value returned by the SQL SELECT VALUE FROM V$PARAMETER WHERE NAME = 'open_cursors'.

AsyncConnection.module: This write-only attribute sets the module column in the v$session table. The maximum length for this string is 48 and if you exceed this length you will get ORA-24960.

AsyncConnection.outputtypehandler

This read-write attribute specifies a method called for each column that is going to be fetched from any cursor associated with this connection. The method signature is handler(cursor, metadata) and the return value is expected to be a variable object or None in which case a default variable object will be created. If this attribute is None, the default behavior will take place for all columns fetched from cursors.

See Changing Fetched Data Types with Output Type Handlers.

AsyncConnection.sdu: This read-only attribute specifies the size of the Session Data Unit (SDU) that is being used by the connection. The value will be the lesser of the requested python-oracledb size and the maximum size allowed by the database network configuration.

AsyncConnection.service_name: This read-only attribute specifies the Oracle Database service name associated with the connection. This is the same value returned by the SQL SELECT SYS_CONTEXT('USERENV', 'SERVICE_NAME') FROM DUAL.

AsyncConnection.stmtcachesize

This read-write attribute specifies the size of the statement cache. This value can make a significant difference in performance if you have a small number of statements that you execute repeatedly.

The default value is 20.

See Statement Caching for more information.

AsyncConnection.thin: This read-only attribute returns a boolean indicating if the connection was established with the python-oracledb Thin mode (True) or python-oracledb Thick mode (False).

AsyncConnection.transaction_in_progress: This read-only attribute specifies whether a transaction is currently in progress on the database associated with the connection.

AsyncConnection.username: This read-only attribute returns the name of the user which established the connection to the database.

AsyncConnection.version: This read-only attribute returns the version of the database to which a connection has been established.