英文:
Rust diesel the trait `load_dsl::private::CompatibleType<PodcastEpisode, Sqlite>` is not implemented for `Untyped
问题
The provided code appears to be in Rust and involves database interactions using Diesel. Here's the translated content without the code:
无法找出以下 PodcastEpisode 结构体在写入以下内容时出现以下错误的原因。错误来自于 conn 并且指出以下内容：
同时，如果我添加这个结构体，应用程序就会启动。尽管该结构体不是 SQL 查询的正确类型，但应用程序可以启动。
相关的表定义如下：
Podcasts 表：
Favorites 表：
Podcast Episodes 表：
完整的代码可以在此处查看。
英文:
I can't find out why the following PodcastEpisode struct
#[derive(Queryable, Identifiable,QueryableByName, Selectable, Debug, PartialEq, Clone, ToSchema,
Serialize, Deserialize)]
pub struct PodcastEpisode {
#[diesel(sql_type = Integer)]
pub(crate) id: i32,
#[diesel(sql_type = Integer)]
pub(crate) podcast_id: i32,
#[diesel(sql_type = Text)]
pub(crate) episode_id: String,
#[diesel(sql_type = Text)]
pub(crate) name: String,
#[diesel(sql_type = Text)]
pub(crate) url: String,
#[diesel(sql_type = Text)]
pub(crate) date_of_recording: String,
#[diesel(sql_type = Text)]
pub image_url: String,
#[diesel(sql_type = Integer)]
pub total_time: i32,
#[diesel(sql_type = Text)]
pub(crate) local_url: String,
#[diesel(sql_type = Text)]
pub(crate) local_image_url: String,
#[diesel(sql_type = Text)]
pub(crate) description: String,
#[diesel(sql_type = Text)]
pub(crate) status: String,
#[diesel(sql_type = Nullable<Date>)]
pub(crate) download_time: Option<NaiveDateTime>
}
is giving this error when the following is written. The error comes from conn and is saying the following
error[E0277]: the trait bound `Untyped: load_dsl::private::CompatibleType<PodcastEpisode, Sqlite>` is not satisfied
--> src\db.rs:755:47
|
755 | let res1 = res.load::<PodcastEpisode>(conn).expect("Error loading \
| ---- ^^^^ the trait `load_dsl::private::CompatibleType<PodcastEpisode, Sqlite>` is not implemented for `Untyped`
| |
| required by a bound introduced by this call
|
= help: the trait `load_dsl::private::CompatibleType<U, DB>` is implemented for `Untyped`
= note: required for `diesel::query_builder::sql_query::UncheckedBind<SqlQuery, &std::string::String, diesel::sql_types::Text>` to implement `LoadQuery<'_, _, PodcastEpisode>`
note: required by a bound in `diesel::RunQueryDsl::load`
--> <path>\src\github.com-1ecc6299db9ec823\diesel-2.0.3\src\query_dsl\mod.rs:1499:15
|
1499 | Self: LoadQuery<'query, Conn, U>,
| ^^^^^^^^^^^^^^^^^^^^^^^^^^ required by this bound in `RunQueryDsl::load`
pub fn get_timeline(username_to_search: String, conn: &mut SqliteConnection) {
let podcast_timeline = sql_query("SELECT podcast_episodes FROM podcasts, podcast_episodes, \
favorites \
WHERE podcasts.id = podcast_episodes.podcast_id AND podcasts.id = favorites.podcast_id AND favorites.username=? AND favored=1 ORDER BY podcast_episodes.date_of_recording DESC");
let res = podcast_timeline.bind::<Text, _>(&username_to_search);
let res1 = res.load::<PodcastEpisode>(conn).expect("Error loading \
podcast \
episode by id");
}
Meanwhile if I add this struct the application starts. It is the wrong type for the sql query but the application starts:
#[derive(Serialize, Deserialize, Queryable, QueryableByName, Clone, ToSchema)]
#[serde(rename_all = "camelCase")]
pub struct PodcastHistoryItem {
#[diesel(sql_type = Integer)]
pub id: i32,
#[diesel(sql_type = Integer)]
pub podcast_id: i32,
#[diesel(sql_type = Text)]
pub episode_id: String,
#[diesel(sql_type = Integer)]
pub watched_time: i32,
#[diesel(sql_type = Text)]
pub date: String,
#[diesel(sql_type = Text)]
pub username: String
}
Relevant table definitions:
Podcasts
diesel::table! {
podcasts (id) {
id -> Integer,
name -> Text,
directory_id -> Text,
rssfeed -> Text,
image_url -> Text,
summary -> Nullable<Text>,
language -> Nullable<Text>,
explicit -> Nullable<Text>,
keywords -> Nullable<Text>,
last_build_date -> Nullable<Text>,
author -> Nullable<Text>,
active -> Bool,
original_image_url -> Text,
directory_name -> Text,
}
}
Favorites:
diesel::table! {
favorites (username, podcast_id) {
username -> Text,
podcast_id -> Integer,
favored -> Bool,
}
}
Podcast Episodes
diesel::table! {
podcast_episodes (id) {
id -> Integer,
podcast_id -> Integer,
episode_id -> Text,
name -> Text,
url -> Text,
date_of_recording -> Text,
image_url -> Text,
total_time -> Integer,
local_url -> Text,
local_image_url -> Text,
description -> Text,
status -> Text,
download_time -> Nullable<Timestamp>,
}
}
The full code can be seen here
答案1
得分: 1
在 table! 宏中定义的类型存在不匹配，download_time 被定义为：
download_time -> Nullable<Timestamp>,
而在结构体中，您将其定义为：
#[diesel(sql_type = Nullable<Date>)]
pub(crate) download_time: Option<NaiveDateTime>
Nullable<Date> 和 Nullable<Timestamp> 不一样。
您可能想在结构体定义中写成 Nullable<Timestamp>。
英文:
There is a mismatch in the defined types, at the table! macro download_time is defined as:
download_time -> Nullable<Timestamp>,
In the struct you define it as:
#[diesel(sql_type = Nullable<Date>)]
pub(crate) download_time: Option<NaiveDateTime>
Nullable<Date> and Nullable<Timestamp> are not the same.
You probably meant to write Nullable<Timestamp> in the struct definition.
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