diesel-rs/diesel

A safe, extensible ORM and Query Builder for Rust – For feature requests and longer questions also see https://github.com/diesel-rs/diesel/discussions/categories/q-a

Georg Semmler

@weiznich

@PlasmaPower Can you provide the a complete reproducing example for that before opening an issue?

Lee Bousfield

@PlasmaPower

With diesel features=["postgres"] :

#[macro_use]
extern crate diesel;

table! {
    examples (id) {
        id -> Int4,
        bytes -> Bytea,
    }
}

// Compiles
#[derive(Queryable)]
struct Example {
    id: i32,
    bytes: [u8; 8],
}

// Doesn't compile
#[derive(Insertable)]
#[table_name = "examples"]
struct NewExample {
    bytes: [u8; 8],
}

let me look at an example without postgres..

Georg Semmler

@weiznich

Have you tried to actually use your struct implementing Queryable? That won't work.

Lee Bousfield

@PlasmaPower

oh, shoot. That's too bad. I guess I'll need a wrapper on both sides then.

thanks

Georg Semmler

@weiznich

The "underlying" issue is that we cannot guarantee that the returned Bytea field is exactly 8 byte. It also can contain more than 8 bytes for the general case.

Lee Bousfield

@PlasmaPower

would this work with a mysql engine BYTES(8)?

Georg Semmler

@weiznich

As diesel only has a general Bytea type this won't help directly. You would probably need to define your own sql type for that and then your definitively back to writing your own conversions there.

Lee Bousfield

@PlasmaPower

alright, thanks

Shao Chenyang

@tzsword

@tzsword Have you tried to put a #[macro_export] on your reexport?

thank you very very very much for reply. I gave up, I added diesel to the required workspace, and gave up paging hahaha~~

for now, my code looks like:

       table
      .filter(available.eq(query.available()))
            .limit(query.limit())
            .offset(query.offset());

diesel is AWESOME~~~

Georg Semmler

@weiznich

:+1:

Pavan Kumar Sunkara

@pksunkara

@tzsword I have actually been looking into this issue last week. The issue is that diesel uses some derive macros inside it non proc macros which is why re-exporting doesn't work. I am planning to solve it soon.

Pavan Kumar Sunkara

@pksunkara

        #[derive(Debug, Clone, Copy, $crate::query_builder::QueryId, Default)]
        pub struct $column_name;

is the offender

Miguel Ping

@mping

Anders Blenstrup-Pedersen

@KatsuoRyuu

matrixbot

@matrixbot

Boblazar Алексей Пастухов (Gitter): йоу

Shao Chenyang

@tzsword

@tzsword I have actually been looking into this issue last week. The issue is that diesel uses some derive macros inside it non proc macros which is why re-exporting doesn't work. I am planning to solve it soon.
Awesomeeeeeeeeeeeeee this is very cool, can I help? I'm a rookie~~

Pavan Kumar Sunkara

@pksunkara

@tzsword You can try to take a stab at it. I am currently a little busy with other stuff. In the file, https://github.com/diesel-rs/diesel/blob/master/diesel/src/macros/mod.rs, we need to remove all $crate::query_builder::QueryId by adding the derived code locally

Pavan Kumar Sunkara

@pksunkara

You know what, I just finished it, diesel-rs/diesel#2579

Just 10 mins work :D

Shao Chenyang

@tzsword

Just 10 mins work :D
:+1:

Pavan Kumar Sunkara

@pksunkara

Looks like nightly is failing for both your "group by" and my PRs. Seems to be an issue with the nightly

Georg Semmler

@weiznich

@pksunkara Can you please open an issue in rust-lang/rust for that? (Maybe we should work on getting diesel into their test suite. It happens quite often lately that they break diesel :disappointed: )

Georg Semmler

@weiznich

@pksunkara I've opened rust-lang/rust#79459

Pavan Kumar Sunkara

@pksunkara

Sorry, I didn't see this before you created the issue

Pavan Kumar Sunkara

@pksunkara

Diesel doesn't currently provide a way to explicitly assign a field to its default value, though it may be provided in the future.

I have been meaning to ask about this. I find that I need to specify DEFAULT in INSERT. I looked at the docs and it looks like it is not supported and this is the closest info I could find. Can you please confirm?

CREATE TABLE users (
    id SERIAL,
    name VARCHAR(255),
    email VARCHAR(255) DEFAULT NULL
);

INSERT INTO users (name, email) VALUES ('John', 'john@gmail.com'), ('Sean', DEFAULT);

Georg Semmler

@weiznich

@pksunkara I wouldn't call that not supported, but more like not exposed as part of the public API. See here for example. Seems like someone need to write some query dsl to expose that publicly.

Erlend Langseth

@Ploppz

Minor problem with the solution of my previous question: m::measurement.count().filter(m::plate_id.eq(p::id)).single_value() turns out to be diesel::sql_types::Nullable<diesel::sql_types::BigInt>. Why is it nullable I wonder. If no such measurements are found it should be 0?

Georg Semmler

@weiznich

In that case it should return 0 for entries, but .single_value() is designed to be used with all subqueries and there some queries return null where no entries are returned.

Erlend Langseth

@Ploppz

hmm ok, then I'll just unwrap

Pavan Kumar Sunkara

@pksunkara

@weiznich I can do that. But wouldn't table! need to know which column has DEFAULT and which doesn't?

That way the following will work.

diesel::insert_into(users).values(&(name.eq("Sean"), email.default)).execute(&conn);

will work. Notice the email.default

Georg Semmler

@weiznich

Probably. I think there must be reason why this is not exposed yet, but I haven't looked in detail yet

Pavan Kumar Sunkara

@pksunkara

I am actually stuck on this so I can immediately start working on this. If you can look into it and give me a bit guidance, that would be great

Georg Semmler

@weiznich

I would probably start with adding some wrapper like struct DefaultValue<C>(C) and implement Insertable<C::Table> for that resulting in Values beingDefault`. Then write some tests and see if it work

Ibraheem Ahmed

@ibraheemdev

How can I build a query like this?

let mut posts_query = schema::posts::table.into_boxed::<Pg>();

if let Some(foo_id) = foo.id {
      posts_query = posts.filter(id.eq(foo_id));
}

if let Some(foo_title) = foo.title {
      posts_query = posts.filter(title.eq(foo_title));
}

if let Some(foo_name) = foo.name {
      posts_query = posts.filter(name.eq(foo_name));
}

I'm getting errors:

  --> src/main.rs:54:21
   |
54 |       posts_query = posts.filter(name.eq(foo_name));
   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `diesel::query_builder::BoxedSelectStatement`, found struct `diesel::query_builder::SelectStatement`

Ibraheem Ahmed

@ibraheemdev

Oh, looks like I have to do: posts_query = posts.filter(id.eq(foo_id)).into_boxed();

The example in the docs does not mention this

Why is it different?

Georg Semmler

@weiznich

Because you construct a new query in each if statement instead modifying the existing query stored in posts_query.

Ibraheem Ahmed

@ibraheemdev

So how do i modify the existing query?

I am doing the same thing as the docs

Georg Semmler

@weiznich

the same thing as in the docs would be something like posts_query = posts_query.filter(id.eq(foo_id)) and not = posts.filter(id.eq(foo_id)).

Ibraheem Ahmed

@ibraheemdev

Oh, I totally missed that

Thanks for catching it

Pavan Kumar Sunkara

@pksunkara

What do you think about the proposal in https://github.com/diesel-rs/diesel/pull/2579#discussion_r531634771?

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