query_strings_as_bytes.py

# -----------------------------------------------------------------------------
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#
# This software is dual-licensed to you under the Universal Permissive License
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# either license.
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# the following applies:
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# Licensed under the Apache License, Version 2.0 (the "License");
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
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# -----------------------------------------------------------------------------

# -----------------------------------------------------------------------------
# query_strings_as_bytes.py
#
# Demonstrates how to query strings as bytes (bypassing decoding of the bytes
# into a Python string). This can be useful when attempting to fetch data that
# was stored in the database in the wrong encoding.
# -----------------------------------------------------------------------------

import oracledb
import sample_env

# determine whether to use python-oracledb thin mode or thick mode
if not sample_env.get_is_thin():
    oracledb.init_oracle_client(lib_dir=sample_env.get_oracle_client())

STRING_VAL = "I bought a cafetière on the Champs-Élysées"


def return_strings_as_bytes(cursor, metadata):
    if metadata.type_code is oracledb.DB_TYPE_VARCHAR:
        return cursor.var(str, arraysize=cursor.arraysize, bypass_decode=True)


connection = oracledb.connect(
    user=sample_env.get_main_user(),
    password=sample_env.get_main_password(),
    dsn=sample_env.get_connect_string(),
)

# truncate table and populate with our data of choice
with connection.cursor() as cursor:
    cursor.execute("truncate table TestTempTable")
    cursor.execute(
        "insert into TestTempTable values (1, :val)", val=STRING_VAL
    )
    connection.commit()

# fetch the data normally and show that it is returned as a string
with connection.cursor() as cursor:
    cursor.execute("select IntCol, StringCol from TestTempTable")
    print("Data fetched using normal technique:")
    for row in cursor:
        print(row)
    print()

# fetch the data, bypassing the decode and show that it is returned as
# bytes
with connection.cursor() as cursor:
    cursor.outputtypehandler = return_strings_as_bytes
    cursor.execute("select IntCol, StringCol from TestTempTable")
    print("Data fetched using bypass decode technique:")
    for row in cursor:
        print(row)