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