feat: allow an easier use of limit/offset

Author: ctron

src/executor/limiter.rs

@@ -0,0 +1,62 @@
+use crate::{
+    ConnectionTrait, DbErr, EntityTrait, FromQueryResult, Paginator, PaginatorTrait, QuerySelect,
+    Select, SelectModel, Selector, SelectorTrait,
+};
+use std::num::NonZeroU64;
+
+#[derive(Debug)]
+pub struct Limiter<'db, C, S>
+where
+    C: ConnectionTrait,
+    S: SelectorTrait + 'db,
+{
+    db: &'db C,
+    selector: Selector<S>,
+    paginator: Paginator<'db, C, S>,
+}
+
+impl<'db, C, S> Limiter<'db, C, S>
+where
+    C: ConnectionTrait,
+    S: SelectorTrait + 'db,
+{
+    pub async fn fetch(self) -> Result<Vec<S::Item>, DbErr> {
+        self.selector.all(self.db).await
+    }
+
+    pub async fn total(&self) -> Result<u64, DbErr> {
+        self.paginator.num_items().await
+    }
+}
+
+pub trait LimiterTrait<'db, C>
+where
+    C: ConnectionTrait,
+{
+    type Selector: SelectorTrait + 'db;
+
+    fn limiting(self, db: &'db C, offset: u64, limit: u64) -> Limiter<'db, C, Self::Selector>;
+}
+
+impl<'db, C, M, E> LimiterTrait<'db, C> for Select<E>
+where
+    C: ConnectionTrait,
+    E: EntityTrait<Model = M>,
+    M: FromQueryResult + Sized + Send + Sync + 'db,
+{
+    type Selector = SelectModel<M>;
+
+    fn limiting(self, db: &'db C, offset: u64, limit: u64) -> Limiter<'db, C, Self::Selector> {
+        let selector = self
+            .clone()
+            .limit(NonZeroU64::new(limit).map(|limit| limit.get()))
+            .offset(NonZeroU64::new(limit).map(|limit| limit.get()))
+            .into_model();
+
+        Limiter {
+            db,
+            paginator: self.clone().paginate(db, 1),
+            selector,
+        }
+    }
+}

src/executor/mod.rs

@@ -2,6 +2,7 @@ mod cursor;
 mod delete;
 mod execute;
 mod insert;
+mod limiter;
 mod paginator;
 mod query;
 mod select;
@@ -11,6 +12,7 @@ pub use cursor::*;
 pub use delete::*;
 pub use execute::*;
 pub use insert::*;
+pub use limiter::*;
 pub use paginator::*;
 pub use query::*;
 pub use select::*;