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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