How to write custom storage engines and triggers in MySQL using Python

How to use Python to write custom storage engines and triggers in MySQL

Introduction:
MySQL is a powerful relational database management system. Allows users to interact with it using multiple programming languages. Among them, Python is a widely used scripting language with simple syntax, easy to learn and use. In MySQL, we can use Python to write custom storage engines and triggers to meet some special needs. This article will introduce in detail how to use Python to write custom storage engines and triggers, and provide specific code examples.

1. Custom storage engine

1. Create a Python script file for a custom storage engine
   First, we need to create a Python script file named "custom_engine.py" (You can name it according to actual needs). In this script file, we need to introduce the MySQLdb module and define a StorageEngine class inherited from MySQLdb, which is the entrance to the custom storage engine.

import MySQLdb

class MyStorageEngine(MySQLdb.StorageEngine):
    def __init__(self):
        MySQLdb.StorageEngine.__init__(self)
        # 在此处进行一些初始化操作
        pass

    def open(self, name, mode='r'):
        # 在此处编写自定义存储引擎的逻辑
        pass

    def create(self, name):
        # 在此处编写自定义存储引擎的逻辑
        pass

    def close(self, name):
        # 在此处编写自定义存储引擎的逻辑
        pass

    def delete(self, name):
        # 在此处编写自定义存储引擎的逻辑
        pass

2. Register a custom storage engine
   Next, we need to use MySQL's "CREATE FUNCTION" statement to register the custom storage engine into MySQL and define its related parameters . Assuming that our database is named "testdb", a custom storage engine can be registered through the following logic:

CREATE FUNCTION my_storage_engine RETURNS INTEGER SONAME 'custom_engine.so';

In the above statement, "my_storage_engine" is the name of the custom storage engine, "custom_engine. so" is a shared library file for a custom storage engine. It should be noted that the shared_library plug-in must be enabled, which can be checked by executing the "SHOW PLUGINS" command.

3. Using a custom storage engine in the table
   When creating a table in our database, you can specify the use of a custom storage engine. For example, we can create a table using a custom storage engine using the following statement:

CREATE TABLE my_table (id INT, name VARCHAR(100)) ENGINE=my_storage_engine;

In this example, "my_table" is the name of the table, and "id" and "name" are the Column, "ENGINE=my_storage_engine" specifies that the storage engine used by the table is our custom storage engine.

2. Custom triggers

1. Create a Python script file for a custom trigger
   Similar to creating a custom storage engine, we need to create a Python script file (for example "custom_trigger.py"), which defines a Trigger class inherited from MySQLdb, which is the entrance to custom triggers.

import MySQLdb

class MyTrigger(MySQLdb.Trigger):
    def __init__(self):
        MySQLdb.Trigger.__init__(self)
        # 在此处进行一些初始化操作
        pass

    def before_insert(self, row):
        # 在此处编写自定义触发器的逻辑
        pass

    def after_insert(self, row):
        # 在此处编写自定义触发器的逻辑
        pass

    def before_update(self, old_row, new_row):
        # 在此处编写自定义触发器的逻辑
        pass

    def after_update(self, old_row, new_row):
        # 在此处编写自定义触发器的逻辑
        pass

    def before_delete(self, row):
        # 在此处编写自定义触发器的逻辑
        pass

    def after_delete(self, row):
        # 在此处编写自定义触发器的逻辑
        pass

2. Register a custom trigger
   We can use MySQL's "CREATE TRIGGER" statement to register a custom trigger into MySQL and specify its related parameters. Assuming that our database is named "testdb", a custom trigger can be registered through the following logic:

CREATE TRIGGER my_trigger BEFORE INSERT ON my_table FOR EACH ROW BEGIN
    CALL my_trigger_func(NEW.id, NEW.name);
END;

In the above statement, "my_trigger" is the name of the custom trigger, "my_table" is the name of the table where the trigger is located, and "my_trigger_func" is the callback function of the trigger.

3. Using custom triggers in tables
   When creating a table in our database, you can specify the use of custom triggers. For example, we can create a custom trigger on the "my_table" table using the following statement:

CREATE TABLE my_table (id INT, name VARCHAR(100));

In this example, the trigger will be fired before the insert operation on the "my_table" table.

Conclusion:
This article introduces how to use Python to write custom storage engines and triggers in MySQL, and provides specific code examples. By customizing storage engines and triggers, we can enhance the functionality and flexibility of MySQL according to actual needs. I hope this article helps you write custom storage engines and triggers in MySQL using Python.

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