diesel-rs/diesel

A safe, extensible ORM and Query Builder for Rust – For feature requests and longer questions also see https://discourse.diesel.rs

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?

Ashwani44

@Ashwani44

Hello everyone,
Does anybody knows about this error:

the trait Queryable<diesel::sql_types::Numeric, Pg> is not implemented for BigDecimal

Here is my model.rs


#![allow(unused)]
#![allow(clippy::all)]
use super::schema::employee;

use chrono::NaiveDateTime;
use bigdecimal::BigDecimal;

#[derive(Queryable, Debug, Identifiable)]
#[table_name = "employee"]
#[primary_key(employee_id)]
pub struct Employee {
    pub employee_id: i32,
    pub name: Option<String>,
    pub age: Option<i32>,
    pub address: Option<String>,
    pub email: Option<String>,
    pub dept_id: i32,
    pub salary: Option<BigDecimal>,
    pub created_on: Option<NaiveDateTime>,
    pub created_by: Option<String>,
    pub modified_on: Option<NaiveDateTime>,
    pub modified_by: Option<String>,
    pub is_active: Option<bool>,
}

main.rs

let employees: Vec<Employee> = employee
        .load::<Employee>(&connection)
        .expect("Error loading employee");

    for emp in employees {
        println!("{}", emp.name.unwrap_or_default());
    }

I am getting this error:

the trait `Queryable<diesel::sql_types::Numeric, Pg>` is not implemented for `BigDecimal`

Ashwani44

@Ashwani44

cargo.toml

[dependencies]
diesel = { version = "1.4.5", features = ["postgres","chrono"] }
dotenv = "0.15.0"
chrono = { version = "0.4.19" , features = ["serde"] }
bigdecimal = { version = "0.2.0" , features = ["serde"] }

Can anybody tell me where I am going wrong ?

Pavan Kumar Sunkara

@pksunkara

@Ashwani44 Add numeric to your diesel features

Ashwani44

@Ashwani44

@pksunkara I added this "diesel = { version = "1.4.5", features = ["postgres","chrono","numeric"] }" but still have the same error

diesel = { version = "1.4.5", features = ["postgres","chrono","numeric"] }

Shao Chenyang

@tzsword

@Ashwani44 diesel need bigdecimal version < 0.2 (bigdecimal >=0.0.10, <0.2.0) try use the 0.1 version of bigdecimal

Ashwani44

@Ashwani44

Alright !! let me try this

@tzsword It's working. Really thanks for this.

Shao Chenyang

@tzsword

glad to help you ~~~~

Shao Chenyang

@tzsword

hello eveyone,

when i run diesel migration run in workspace_a,
diesel will add contents of all workspaces/migrations to the workspace_a/src/schema.rs
how to avoid this? let workspace_a/src/schema.rs just have the content of workspace_a/migrations?

project
│   migrations    --- common global database schemas
│   diesel.toml   --- [print_schema] file = "src/schema.rs"
│   │
│   └───src
│       │   schema.rs
│       │   ...
│
└───workspace_a
│   │
│   │   migrations    --- workspace_a database schemas
│   │   diesel.toml   --- [print_schema] file = "src/schema.rs"
│   └───src
│       │   schema.rs
│       │   ...
│   
└───workspace_b
│   │   migrations    --- workspace_a database schemas
│   │   diesel.toml   --- [print_schema] file = "src/schema.rs"
│   └───src
│       │   schema.rs
│       │   ...

2 replies

please forgive my kindergarten Chingenglish haha~~~

Ibraheem Ahmed

@ibraheemdev

Is this query possible with the dsl? select sum(t.total) from (select rate * time_spent as total from tasks) as t

1 reply

Ashwani44

@Ashwani44

Does anybody has any idea about this error:

^^^^^^^^^^^^^^^^ `std::result::Result<_, diesel::result::Error>` cannot be formatted with the default formatter

here is my code:

 let total_department = department.count().get_result(&connection);
    println!("{}", total_department);

Shao Chenyang

@tzsword

@Ashwani44 try this:

let total_department: i64 = department
    .count()
    .get_result(&conn)
    .expect("Error counting cute kittens");
println!("{}", total_department);

Francis Le Roy

@GrandChaman_gitlab

Hi ! I've got a problem applying pending migration from the executable directly. The first time the migration are applied, everything is fine and the table __diesel_schema_migrations is created in the public schema.

All my table are in a separate schema, when I retry to apply the migration, it fails and creates a new table __diesel_schema_migrations in the new schema.

I am not using -csearch_path in the connection string.

How could I force diesel to use the public schema for its __diesel_schema_migrations table ?

2 replies

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