error[E0277]: the trait bound MyEnum: diesel::Expression is not satisfied
--> tests\custom_types.rs:50:10
|
50 | #[derive(Insertable, Queryable, Identifiable, Debug, PartialEq)]
| ^^^^^^^^^^ the trait diesel::Expression is not implemented for MyEnum
|
= note: required because of the requirements on the impl of diesel::expression::AsExpression<MyEnum> for MyEnum
= note: this error originates in a derive macro (in Nightly builds, run with -Z macro-backtrace for more info)

This error message indicates that you did not add a valid #[sql_type = "SomeSqlTypeSupportedByMysql"] annotation.

Hi, how did you find the reason for that error message from the source code? I found, in rust, error message sometimes is very confusing. I was looking into code for AsExpression.

In MySQL you can do:

INSERT INTO table (column_list)
VALUES (value_list)
ON DUPLICATE KEY UPDATE
   c1 = v1, 
   c2 = v2,
   ...;

And in PostgreSQL you can do:

INSERT INTO the_table (id, column_1, column_2) 
VALUES (1, 'A', 'X'), (2, 'B', 'Y'), (3, 'C', 'Z')
ON CONFLICT (id) DO UPDATE 
  SET column_1 = excluded.column_1, 
      column_2 = excluded.column_2;

How can you do this in Diesel?

Reading about this, it seems like it was unsafe in some way to do this before they implemented the ON CONFLICT clause in PostgreSQL: https://stackoverflow.com/questions/1109061/insert-on-duplicate-update-in-postgresql

So I'm hoping it can be done "atomically" with a single query.

https://docs.diesel.rs/1.4.x/diesel/fn.insert_or_ignore_into.html
Looks like PostgreSQL support is better in quite a few ways. Seems like this feature is implemented for PostgreSQL but not MySQL. I can't switch to PostgreSQL, but I will in future projects.

For now, I think I'll do two queries:

• insert_or_ignore_into
• update