Migrating from cx_Oracle to oracledb: Understanding Bind Parameters by Array Index

Introduction

As developers, we often find ourselves dealing with different database libraries and their respective features. When migrating code from one library to another, it’s not uncommon to encounter differences in how certain features are implemented. In this article, we’ll explore the difference between bind parameters in cx_Oracle and oracledb, specifically focusing on bind parameters by array index.

Understanding Bind Parameters

Bind parameters are a way to pass data from your application code into SQL statements. They allow you to treat user input as safe, reducing the risk of SQL injection attacks. In both cx_Oracle and oracledb, bind parameters can be used in two ways: named binds and positional binds.

Named Bind Variables

Named bind variables are used by specifying a colon followed by the variable name in the SQL statement. This approach is safer because it allows you to specify the data type of the bound value, which helps prevent SQL injection attacks. For example:

UPDATE command_center SET 
    E_ID = :1,
    E_ASPECTS = :2,
    E_CREATED_TIMESTAMP = :3
WHERE e_id = :1;

In cx_Oracle, named bind variables are enabled by default.

Positional Bind Variables

Positional bind variables, on the other hand, use an array index to pass values. They require you to specify the number of positional binds in the SQL statement and then pass them as an array. The bind value is passed at a specific position in the array.

UPDATE command_center SET 
    E_ID = :1,
    E_ASPECTS = :2,
    E_CREATED_TIMESTAMP = :3
WHERE e_id = :1;

In cx_Oracle, positional bind variables can be used without needing to explicitly specify the number of binds. However, this approach can lead to issues if not implemented correctly.

Migrating from cx_Oracle to oracledb

When migrating code from cx_Oracle to oracledb, you may encounter differences in how bind parameters are handled. In particular, cx_Oracle’s positional bind variable behavior is not supported by default in oracledb.

Enabling Thick Mode

One way to overcome this limitation is to enable thick mode for your oracledb connection. Thick mode enables Python-level support for the Oracle JDBC/ODBC type map, allowing you to use a more traditional SQL API.

To enable thick mode, you can add the following configuration options when creating your oracledb connection:

import oracledb

connection = await oracledb.connect(
    user="username",
    password="password",
    dsn="dsn",
    encoding="UTF-8",
    connect_string=f"SERVICE_NAME={service_name};UID={user};PWD={password}",
    version=oracledb.V2,
    mode=oracledb.MODE_THICK
)

Using Named Bind Variables

Instead of relying on positional bind variables, it’s recommended to use named binds. This approach is safer and more flexible because you can specify the data type of each bound value.

For example:

def bulk_insert_or_update_data_to_targets(self, sql, target_data, id_index=0):
    for target_connections, data in target_data:
        for con in target_connections:
            cursor = con.cursor()
            cursor.execute(sql,
                           {"id": :1, "aspect": :2, "created_timestamp": :3},
                           batcherrors=True)
            if cursor.getbatcherrors():
                self.logger.debug("data: " + str(data))
            cursor.close()

In this example, the execute method takes a dictionary of bind variables and their corresponding positional indices. The :1, :2, and :3 placeholders are replaced with the actual values from the data list.

Conclusion

Migrating from cx_Oracle to oracledb requires attention to differences in how bind parameters are handled. By enabling thick mode and using named binds, you can overcome the limitations of positional bind variables and ensure a safer and more flexible way of passing data into your SQL statements.

Last modified on 2024-09-10