123 lines
5.5 KiB
Python
123 lines
5.5 KiB
Python
#------------------------------------------------------------------------------
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# Copyright (c) 2019, 2022, Oracle and/or its affiliates.
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#
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# This software is dual-licensed to you under the Universal Permissive License
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# (UPL) 1.0 as shown at https://oss.oracle.com/licenses/upl and Apache License
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# 2.0 as shown at http://www.apache.org/licenses/LICENSE-2.0. You may choose
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# either license.
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#
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# If you elect to accept the software under the Apache License, Version 2.0,
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# the following applies:
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#------------------------------------------------------------------------------
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#------------------------------------------------------------------------------
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# session_callback_plsql.py
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#
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# Demonstrates how to use a connection pool session callback written in
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# PL/SQL. The callback is invoked whenever the tag requested by the application
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# does not match the tag associated with the session in the pool. It should be
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# used to set session state, so that the application can count on known session
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# state, which allows the application to reduce the number of round trips to the
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# database.
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#
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# The primary advantage to this approach over the equivalent approach shown in
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# session_callback.py is when DRCP is used, as the callback is invoked on the
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# server and no round trip is required to set state.
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#
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# Also see session_callback.py
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#------------------------------------------------------------------------------
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import oracledb
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import sample_env
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# this script is currently only supported in python-oracledb thick mode
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oracledb.init_oracle_client(lib_dir=sample_env.get_oracle_client())
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# create pool with session callback defined
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pool = oracledb.create_pool(user=sample_env.get_main_user(),
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password=sample_env.get_main_password(),
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dsn=sample_env.get_connect_string(), min=2, max=5,
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increment=1,
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session_callback="pkg_SessionCallback.TheCallback")
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# truncate table logging calls to PL/SQL session callback
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with pool.acquire() as conn:
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cursor = conn.cursor()
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cursor.execute("truncate table PLSQLSessionCallbacks")
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# acquire session without specifying a tag; the callback will not be invoked as
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# a result and no session state will be changed
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print("(1) acquire session without tag")
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with pool.acquire() as conn:
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cursor = conn.cursor()
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cursor.execute("select to_char(current_date) from dual")
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result, = cursor.fetchone()
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print("main(): result is", repr(result))
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# acquire session, specifying a tag; since the session returned has no tag,
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# the callback will be invoked; session state will be changed and the tag will
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# be saved when the connection is closed
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print("(2) acquire session with tag")
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with pool.acquire(tag="NLS_DATE_FORMAT=SIMPLE") as conn:
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cursor = conn.cursor()
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cursor.execute("select to_char(current_date) from dual")
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result, = cursor.fetchone()
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print("main(): result is", repr(result))
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# acquire session, specifying the same tag; since a session exists in the pool
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# with this tag, it will be returned and the callback will not be invoked but
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# the connection will still have the session state defined previously
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print("(3) acquire session with same tag")
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with pool.acquire(tag="NLS_DATE_FORMAT=SIMPLE") as conn:
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cursor = conn.cursor()
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cursor.execute("select to_char(current_date) from dual")
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result, = cursor.fetchone()
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print("main(): result is", repr(result))
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# acquire session, specifying a different tag; since no session exists in the
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# pool with this tag, a new session will be returned and the callback will be
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# invoked; session state will be changed and the tag will be saved when the
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# connection is closed
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print("(4) acquire session with different tag")
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with pool.acquire(tag="NLS_DATE_FORMAT=FULL;TIME_ZONE=UTC") as conn:
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cursor = conn.cursor()
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cursor.execute("select to_char(current_date) from dual")
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result, = cursor.fetchone()
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print("main(): result is", repr(result))
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# acquire session, specifying a different tag but also specifying that a
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# session with any tag can be acquired from the pool; a session with one of the
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# previously set tags will be returned and the callback will be invoked;
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# session state will be changed and the tag will be saved when the connection
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# is closed
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print("(4) acquire session with different tag but match any also specified")
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with pool.acquire(tag="NLS_DATE_FORMAT=FULL;TIME_ZONE=MST", matchanytag=True) \
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as conn:
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cursor = conn.cursor()
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cursor.execute("select to_char(current_date) from dual")
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result, = cursor.fetchone()
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print("main(): result is", repr(result))
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# acquire session and display results from PL/SQL session logs
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with pool.acquire() as conn:
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cursor = conn.cursor()
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cursor.execute("""
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select RequestedTag, ActualTag
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from PLSQLSessionCallbacks
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order by FixupTimestamp""")
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print("(5) PL/SQL session callbacks")
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for requestedTag, actualTag in cursor:
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print("Requested:", requestedTag, "Actual:", actualTag)
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