array_dml_rowcounts.py

# -----------------------------------------------------------------------------
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# -----------------------------------------------------------------------------

# -----------------------------------------------------------------------------
# array_dml_rowcounts.py
#
# Demonstrates the use of the 12.1 feature that allows cursor.executemany()
# to return the number of rows affected by each individual execution as a list.
# The parameter "arraydmlrowcounts" must be set to True in the call to
# cursor.executemany() after which cursor.getarraydmlrowcounts() can be called.
# -----------------------------------------------------------------------------

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())

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

with connection.cursor() as cursor:
    # show the number of rows for each parent ID as a means of verifying the
    # output from the delete statement
    for parent_id, count in cursor.execute(
        """
        select ParentId, count(*)
        from ChildTable
        group by ParentId
        order by ParentId
        """
    ):
        print("Parent ID:", parent_id, "has", int(count), "rows.")
    print()

    # delete the following parent IDs only
    parent_ids_to_delete = [20, 30, 50]

    print("Deleting Parent IDs:", parent_ids_to_delete)
    print()

    # enable array DML row counts for each iteration executed in executemany()
    cursor.executemany(
        "delete from ChildTable where ParentId = :1",
        [(i,) for i in parent_ids_to_delete],
        arraydmlrowcounts=True,
    )

    # display the number of rows deleted for each parent ID
    row_counts = cursor.getarraydmlrowcounts()
    for parent_id, count in zip(parent_ids_to_delete, row_counts):
        print("Parent ID:", parent_id, "deleted", count, "rows.")