Uuid with MySQL(MariaDB), using existing sql_type=Binary

[AlexStorm1313]

Here we create the uuid:Uuid(crate) to UUID(custom sql type) conversion using the existing Binary sql type.

use std::io::Write;

use diesel::{
    backend::Backend,
    deserialize::{self, FromSql, FromSqlRow},
    expression::AsExpression,
    mysql::Mysql,
    serialize::{self, IsNull, Output, ToSql},
    sql_types::{self, Binary},
};

/// This struct is a wrapper struct around the uuid:Uuid where we implement our derives etc.
#[derive(Debug, Clone, AsExpression, FromSqlRow)] //<-- 'AsExpression', 'FromSqlRow' are needed for this conversion
#[diesel(sql_type = sql_types::Binary)] //<-- Use existing sql_type
pub struct UUID(pub uuid::Uuid); //<-- Wrap the uuid::Uuid in our custom type

impl From<UUID> for uuid::Uuid { //<-- From implementation for converting from UUID to a uuid:Uuid
    fn from(value: UUID) -> Self {
        value.0
    }
}

impl Into<UUID> for uuid::Uuid { //<-- Into implementation for converting from uuid:Uuid to a  UUID
    fn into(self) -> UUID {
        UUID(self)
    }
}

impl ToSql<Binary, Mysql> for UUID { //<-- Here we convert the Binary data to our own UUID(uuid:Uuid) so rust can use it
    fn to_sql<'b>(&'b self, out: &mut Output<'b, '_, Mysql>) -> serialize::Result {
        Write::write_all(out, self.0.as_bytes().as_slice())?;

        Ok(IsNull::No)
    }
}

impl FromSql<Binary, Mysql> for UUID { //<-- Here we convert the UUID(uuid:Uuid) data to Binary so the database can understand and insert/select this data
    fn from_sql(bytes: <Mysql as Backend>::RawValue<'_>) -> deserialize::Result<Self> {
        Ok(UUID(uuid::Uuid::from_slice(bytes.as_bytes())?))
    }
}

After we finish the conversion implementation we can use the regular uuid:Uuid field in out struct Example:

#[derive(Debug, Clone, Queryable, Selectable, AsChangeset)]
#[diesel(table_name=schema, primary_key(id))]
pub struct Model {
    #[diesel(deserialize_as = UUID, serialize_as = UUID, sql_type = Binary)] //<-- This tells diesel to use the above implementation to convert this to and from Binary when insert/selecting from the database. Optionally you can specify the sql_type here
    pub uuid: uuid::Uuid,
}

Feel free to ask questions or suggest improvement.

Hope this helps some people ✌️