MySQL解析器的扩展开发案例分析:从理论到实践实用指南

// 添加新的关键字
// 在 lexer.yy 文件中添加新的关键字
"MY_CUSTOM_KEYWORD" { return MY_CUSTOM_KEYWORD; }
// 在 parser.yy 文件中添加新的语法规则
custom_statement:
    MY_CUSTOM_KEYWORD expression
    {
        $$ = new CustomStatement($2);
    }
    ;
// 在 semantic_analyzer.cpp 文件中添加新的语义处理逻辑
bool CustomStatement::prepare(THD *thd) {
    // 处理自定义语句的语义
    return false;
}
// 在 optimizer.cpp 文件中添加新的执行计划生成逻辑
bool CustomStatement::optimize() {
    // 生成自定义语句的执行计划
    return false;
}

// 插件初始化函数
static int plugin_init(void *p) {
    // 注册自定义语法处理函数
    mysql_register_custom_sql_handler("MY_CUSTOM_COMMAND", handle_custom_command);
    return 0;
}
// 插件解构函数
static int plugin_deinit(void *p) {
    // 清理资源
    return 0;
}
// 自定义命令处理函数
static bool handle_custom_command(THD *thd, const char *command, size_t length) {
    // 处理自定义命令
    return false;
}
// 插件声明
struct st_mysql_plugin plugin = {
    MYSQL_PLUGIN_INTERFACE_VERSION,
    MYSQL_SERVER_PLUGIN,
    "custom_plugin",
    "Author",
    "Custom plugin for MySQL",
    PLUGIN_LICENSE_GPL,
    plugin_init,
    plugin_deinit,
    NULL,
    NULL,
    NULL,
    0,
    NULL,
    NULL,
    NULL
};

import mysql.connector
from mysql.connector import errorcode
class MySQLProxy:
    def __init__(self, host, port, user, password, database):
        self.host = host
        self.port = port
        self.user = user
        self.password = password
        self.database = database
        self.connection = None
    def connect(self):
        try:
            self.connection = mysql.connector.connect(
                host=self.host,
                port=self.port,
                user=self.user,
                password=self.password,
                database=self.database
            )
            return True
        except mysql.connector.Error as err:
            if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
                print("Something is wrong with your user name or password")
            elif err.errno == errorcode.ER_BAD_DB_ERROR:
                print("Database does not exist")
            else:
                print(err)
            return False
    def execute(self, sql):
        # 解析和转换 SQL 语句
        transformed_sql = self.transform_sql(sql)
        # 执行转换后的 SQL 语句
        cursor = self.connection.cursor()
        cursor.execute(transformed_sql)
        result = cursor.fetchall()
        cursor.close()
        return result
    def transform_sql(self, sql):
        # 转换自定义语法为标准 SQL
        if sql.startswith("MY_CUSTOM_COMMAND"):
            # 转换为标准 SQL
            return "SELECT * FROM table WHERE condition"
        return sql
    def close(self):
        if self.connection:
            self.connection.close()

// 自定义解析器
class CustomParser {
public:
    CustomParser() {}
    ~CustomParser() {}
    // 解析 SQL 语句
    bool parse(const std::string& sql) {
        // 词法分析
        Lexer lexer(sql);
        Token token;
        while (lexer.get_next_token(token)) {
            // 处理词法单元
        }
        // 语法分析
        Parser parser(lexer);
        ASTNode* ast = parser.parse();
        if (!ast) {
            return false;
        }
        // 语义分析
        SemanticAnalyzer analyzer;
        if (analyzer.analyze(ast)) {
            return false;
        }
        // 生成执行计划
        ExecutionPlan plan;
        if (plan.generate(ast)) {
            return false;
        }
        // 执行计划
        if (plan.execute()) {
            return false;
        }
        return true;
    }
};