使用IDbCommandInterceptor解决EF-CORE-3.x-使用MYSQL时,未正常的生成LIKE查询语句

使用EF Core 3.x+Mysql 时,如下EF表达式

var list=await ctx.Set<User>().where(v=>v.Account.Contains("test")).ToListAsync();

生成的语句:

SELECT 
    `b1`.`id`,
    `b1`.`account`,
     ...
FROM
    `basis_user` AS `b1`
WHERE
    LOCATE(CONVERT( 'test' USING UTF8MB4) COLLATE utf8mb4_bin,
            `b1`.`account`) > 0

其中 LOCATE(CONVERT( 'test' USING UTF8MB4) COLLATE utf8mb4_bin,`b1`.`account`) > 0是数据库函数操作,数量量大时,会非常慢.
解决办法:拦截EF生成的语句,将上述函数操作,替换成like

伪代码如下:

1:定义拦截器

public class FmtCommandInterceptor : DbCommandInterceptor, IDbCommandInterceptor
    { 
        public static readonly Regex Regex_Replace_MySql_Like
                = new Regex(@"LOCATE(CONVERT('(?<v>.+?)' USING utf8mb4) COLLATE utf8mb4_bin, (?<k>`.+`?)) > 0", 
                            RegexOptions.Compiled | RegexOptions.IgnoreCase);
       public override InterceptionResult<DbDataReader> ReaderExecuting(DbCommand command, CommandEventData eventData, InterceptionResult<DbDataReader> result)
        {
            command.CommandText = Regex_Replace_MySql_Like.Replace(command.CommandText, " ${k} like '%${v}%' ");
            return base.ReaderExecuting(command, eventData, result);
        }

        public override Task<InterceptionResult<DbDataReader>> ReaderExecutingAsync(DbCommand command, CommandEventData eventData, InterceptionResult<DbDataReader> result, CancellationToken cancellationToken = default)
        { 
            command.CommandText = Regex_Replace_MySql_Like.Replace(command.CommandText, " ${k} like '%${v}%' ");  
            return base.ReaderExecutingAsync(command, eventData, result, cancellationToken);
        }
    }

2:注册拦截器

                services 
                .AddDbContextPool<yearDbContext>(o =>
                {
                    o.UseMySql(Configuration.GetConnectionString("youdbConfigName"), mySqlOptions =>
                    {
                        mySqlOptions.ServerVersion(new Version(5, 6, 40), ServerType.MySql);
                    }).AddInterceptors(new FmtCommandInterceptor()); 
                })

有其它场景时,也可以优化上面的正则替换方法,达到替换执行语句的效果

大家如果有其它办法处理这类问题,也麻烦分享一下

原文地址:https://www.cnblogs.com/qq156864683/p/12732955.html