使用IDbCommandInterceptor解决EF-CORE-3.x-使用MYSQL时,未正常的生成LIKE查询语句
- 作者: A户外军用品A
- 来源: 51数据库
- 2021-08-11
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
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