Some Linq methods are not translated into database functions

[maliming]

NHibernate nuget v5.2.1
hibernate.config:

<?xml version="1.0" encoding="UTF-8"?>
<hibernate-configuration xmlns="urn:nhibernate-configuration-2.2">
  <session-factory>
    <property name="connection.connection_string">server=127.0.0.1;port=5432;database=aspnet_core_app;user id=postgres;password=***;</property>
    <property name="dialect">NHibernate.Dialect.PostgreSQL83Dialect</property>
    <property name="connection.driver_class">NHibernate.Extensions.NpgSql.NpgSqlDriver,NHibernate.Extensions.NpgSql</property>
    <property name="show_sql">true</property>
    <property name="format_sql">true</property>
    <property name="adonet.batch_size">10</property>
    <mapping assembly="WebTest" />
  </session-factory>
</hibernate-configuration>

I use NHibernate.AspNetCore.Identity will have the following problems.(I believe that it also exists in NHibernate.AspNet.Identity)

Sample linq code:

var admin = manager.Users.
Where(x => x.UserName.ToUpper() == "admin".ToUpper()).
Select(x => x.UserName).FirstOrDefault();

Intercepted sql statement:

select
	applicatio0_1_.user_name as col_0_0_ 
from
	public.application_users applicatio0_ 
inner join
	public.aspnet_users applicatio0_1_ 
			on applicatio0_.id=applicatio0_1_.Id 
where
	upper(applicatio0_1_.user_name)='ADMIN' limit 1;

Can query the information of the user admin, so far so good. When I change the current thread culture.
Still the same linq code:

Thread.CurrentThread.CurrentCulture = new CultureInfo("tr");
var admin2 = manager.Users.
Where(x => x.UserName.ToUpper() == "admin".ToUpper()).
Select(x => x.UserName).FirstOrDefault();

Intercepted sql statement:

select
	applicatio0_1_.user_name as col_0_0_ 
from
	public.application_users applicatio0_ 
inner join
	public.aspnet_users applicatio0_1_ 
			on applicatio0_.id=applicatio0_1_.Id 
where
	upper(applicatio0_1_.user_name)='ADMİN' limit 1;

In the current culture, the uppercase of admin is no longer ADMIN but ADMİN

ADMİN ≠ ADMIN

Can't find any user information.

I think the linq method should be translated into something like the following(The method of the parameter is also translated into a database function. by the way: EF will do this):

select
	applicatio0_1_.user_name as col_0_0_ 
from
	public.application_users applicatio0_ 
inner join
	public.aspnet_users applicatio0_1_ 
		on applicatio0_.id=applicatio0_1_.Id 
where
	upper(applicatio0_1_.user_name)=upper('admin') limit 1;

upper(applicatio0_1_.user_name)=upper('admin')

[bahusoid]

If you don't want to use culture specific comparisons you shouldn't use ToUpper method. Use ToUpperInvariant instead.

[maliming]

Thanks @bahusoid
Is it possible to customize the way this translates linq method?
I still feel better to convert to a database function.

[fredericDelaporte]

I still feel better to convert to a database function.

There are no ways of doing this currently, unless maybe using some very hacky workaround like x.UserName.ToUpper() == ("admin" + x.UserName.ToUpper()).SubString(0, "admin".Length).ToUpper().
(The workaround idea is to cause the expression to be no more evaluatable before running the query.)

Something like #1868 would be required to give a way to force ToUpper to be translated to a function call instead of being pre-evaluated when possible.