[PIP] Simple data loader

src/entity/prelude.rs

@@ -1,8 +1,9 @@
 pub use crate::{
     error::*, ActiveEnum, ActiveModelBehavior, ActiveModelTrait, ColumnDef, ColumnTrait,
     ColumnType, CursorTrait, DatabaseConnection, DbConn, EntityName, EntityTrait, EnumIter,
-    ForeignKeyAction, Iden, IdenStatic, Linked, ModelTrait, PaginatorTrait, PrimaryKeyToColumn,
-    PrimaryKeyTrait, QueryFilter, QueryResult, Related, RelationDef, RelationTrait, Select, Value,
+    ForeignKeyAction, Iden, IdenStatic, Linked, LoaderTrait, ModelTrait, PaginatorTrait,
+    PrimaryKeyToColumn, PrimaryKeyTrait, QueryFilter, QueryResult, Related, RelationDef,
+    RelationTrait, Select, Value,
 };
 
 #[cfg(feature = "macros")]

src/query/loader.rs

@@ -0,0 +1,339 @@
+use crate::{
+    ColumnTrait, Condition, ConnectionTrait, DbErr, EntityTrait, Identity, ModelTrait, QueryFilter,
+    Related, RelationType, Select,
+};
+use async_trait::async_trait;
+use sea_query::{Expr, IntoColumnRef, SimpleExpr, ValueTuple};
+use std::{collections::HashMap, str::FromStr};
+
+/// A trait for basic Dataloader
+#[async_trait]
+pub trait LoaderTrait {
+    /// Source model
+    type Model: ModelTrait;
+
+    /// Used to eager load has_one relations
+    async fn load_one<R, C>(&self, stmt: Select<R>, db: &C) -> Result<Vec<Option<R::Model>>, DbErr>
+    where
+        C: ConnectionTrait,
+        R: EntityTrait,
+        R::Model: Send + Sync,
+        <<Self as LoaderTrait>::Model as ModelTrait>::Entity: Related<R>;
+
+    ///  Used to eager load has_many relations
+    async fn load_many<R, C>(&self, stmt: Select<R>, db: &C) -> Result<Vec<Vec<R::Model>>, DbErr>
+    where
+        C: ConnectionTrait,
+        R: EntityTrait,
+        R::Model: Send + Sync,
+        <<Self as LoaderTrait>::Model as ModelTrait>::Entity: Related<R>;
+}
+
+#[async_trait::async_trait]
+impl<M> LoaderTrait for Vec<M>
+where
+    M: ModelTrait,
+    Vec<M>: Sync,
+{
+    type Model = M;
+
+    async fn load_one<R, C>(&self, stmt: Select<R>, db: &C) -> Result<Vec<Option<R::Model>>, DbErr>
+    where
+        C: ConnectionTrait,
+        R: EntityTrait,
+        R::Model: Send + Sync,
+        <<Self as LoaderTrait>::Model as ModelTrait>::Entity: Related<R>,
+    {
+        let rel_def = <<<Self as LoaderTrait>::Model as ModelTrait>::Entity as Related<R>>::to();
+
+        // we verify that is has_one relation
+        match (rel_def).rel_type {
+            RelationType::HasOne => (),
+            RelationType::HasMany => {
+                return Err(DbErr::Type("Relation is HasMany instead of HasOne".into()))
+            }
+        }
+
+        let keys: Vec<ValueTuple> = self
+            .iter()
+            .map(|model: &M| extract_key(&rel_def.from_col, model))
+            .collect();
+
+        let condition = prepare_condition::<<R as EntityTrait>::Model>(&rel_def.to_col, &keys);
+
+        let stmt = <Select<R> as QueryFilter>::filter(stmt, condition);
+
+        let data = stmt.all(db).await?;
+
+        let hashmap: HashMap<String, <R as EntityTrait>::Model> = data.into_iter().fold(
+            HashMap::<String, <R as EntityTrait>::Model>::new(),
+            |mut acc: HashMap<String, <R as EntityTrait>::Model>,
+             value: <R as EntityTrait>::Model| {
+                {
+                    let key = extract_key(&rel_def.to_col, &value);
+
+                    acc.insert(format!("{:?}", key), value);
+                }
+
+                acc
+            },
+        );
+
+        let result: Vec<Option<<R as EntityTrait>::Model>> = keys
+            .iter()
+            .map(|key| hashmap.get(&format!("{:?}", key)).cloned())
+            .collect();
+
+        Ok(result)
+    }
+
+    async fn load_many<R, C>(&self, stmt: Select<R>, db: &C) -> Result<Vec<Vec<R::Model>>, DbErr>
+    where
+        C: ConnectionTrait,
+        R: EntityTrait,
+        R::Model: Send + Sync,
+        <<Self as LoaderTrait>::Model as ModelTrait>::Entity: Related<R>,
+    {
+        let rel_def = <<<Self as LoaderTrait>::Model as ModelTrait>::Entity as Related<R>>::to();
+
+        // we verify that is has_many relation
+        match (rel_def).rel_type {
+            RelationType::HasMany => (),
+            RelationType::HasOne => {
+                return Err(DbErr::Type("Relation is HasOne instead of HasMany".into()))
+            }
+        }
+
+        let keys: Vec<ValueTuple> = self
+            .iter()
+            .map(|model: &M| extract_key(&rel_def.from_col, model))
+            .collect();
+
+        let condition = prepare_condition::<<R as EntityTrait>::Model>(&rel_def.to_col, &keys);
+
+        let stmt = <Select<R> as QueryFilter>::filter(stmt, condition);
+
+        let data = stmt.all(db).await?;
+
+        let mut hashmap: HashMap<String, Vec<<R as EntityTrait>::Model>> =
+            keys.iter()
+                .fold(HashMap::new(), |mut acc, key: &ValueTuple| {
+                    acc.insert(format!("{:?}", key), Vec::new());
+
+                    acc
+                });
+
+        data.into_iter()
+            .for_each(|value: <R as EntityTrait>::Model| {
+                let key = extract_key(&rel_def.to_col, &value);
+
+                let vec = hashmap
+                    .get_mut(&format!("{:?}", key))
+                    .expect("Failed at finding key on hashmap");
+
+                vec.push(value);
+            });
+
+        let result: Vec<Vec<R::Model>> = keys
+            .iter()
+            .map(|key: &ValueTuple| {
+                hashmap
+                    .get(&format!("{:?}", key))
+                    .cloned()
+                    .unwrap_or_default()
+            })
+            .collect();
+
+        Ok(result)
+    }
+}
+
+fn extract_key<Model>(target_col: &Identity, model: &Model) -> ValueTuple
+where
+    Model: ModelTrait,
+{
+    match target_col {
+        Identity::Unary(a) => {
+            let column_a =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &a.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column A:1"));
+            ValueTuple::One(model.get(column_a))
+        }
+        Identity::Binary(a, b) => {
+            let column_a =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &a.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column A:2"));
+            let column_b =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &b.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column B:2"));
+            ValueTuple::Two(model.get(column_a), model.get(column_b))
+        }
+        Identity::Ternary(a, b, c) => {
+            let column_a =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &a.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column A:3"));
+            let column_b =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &b.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column B:3"));
+            let column_c =
+                <<<Model as ModelTrait>::Entity as EntityTrait>::Column as FromStr>::from_str(
+                    &c.to_string(),
+                )
+                .unwrap_or_else(|_| panic!("Failed at mapping string to column C:3"));
+            ValueTuple::Three(
+                model.get(column_a),
+                model.get(column_b),
+                model.get(column_c),
+            )
+        }
+    }
+}
+
+fn prepare_condition<M>(col: &Identity, keys: &[ValueTuple]) -> Condition
+where
+    M: ModelTrait,
+{
+    match col {
+        Identity::Unary(column_a) => {
+            let column_a: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_a.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *A:1"));
+            Condition::all().add(ColumnTrait::is_in(
+                &column_a,
+                keys.iter().cloned().flatten(),
+            ))
+        }
+        Identity::Binary(column_a, column_b) => {
+            let column_a: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_a.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *A:2"));
+            let column_b: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_b.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *B:2"));
+            Condition::all().add(
+                Expr::tuple([
+                    SimpleExpr::Column(column_a.into_column_ref()),
+                    SimpleExpr::Column(column_b.into_column_ref()),
+                ])
+                .in_tuples(keys.iter().cloned()),
+            )
+        }
+        Identity::Ternary(column_a, column_b, column_c) => {
+            let column_a: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_a.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *A:3"));
+            let column_b: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_b.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *B:3"));
+            let column_c: <M::Entity as EntityTrait>::Column =
+                <<M::Entity as EntityTrait>::Column as FromStr>::from_str(&column_c.to_string())
+                    .unwrap_or_else(|_| panic!("Failed at mapping string to column *C:3"));
+            Condition::all().add(
+                Expr::tuple([
+                    SimpleExpr::Column(column_a.into_column_ref()),
+                    SimpleExpr::Column(column_b.into_column_ref()),
+                    SimpleExpr::Column(column_c.into_column_ref()),
+                ])
+                .in_tuples(keys.iter().cloned()),
+            )
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    #[tokio::test]
+    async fn test_load_one() {
+        use crate::{
+            entity::prelude::*, tests_cfg::*, DbBackend, IntoMockRow, LoaderTrait, MockDatabase,
+        };
+
+        let db = MockDatabase::new(DbBackend::Postgres)
+            .append_query_results(vec![vec![
+                cake::Model {
+                    id: 1,
+                    name: "New York Cheese".to_owned(),
+                }
+                .into_mock_row(),
+                cake::Model {
+                    id: 2,
+                    name: "London Cheese".to_owned(),
+                }
+                .into_mock_row(),
+            ]])
+            .into_connection();
+
+        let fruits = vec![fruit::Model {
+            id: 1,
+            name: "Apple".to_owned(),
+            cake_id: Some(1),
+        }];
+
+        let cakes = fruits
+            .load_one(cake::Entity::find(), &db)
+            .await
+            .expect("Should return something");
+
+        assert_eq!(
+            cakes,
+            vec![Some(cake::Model {
+                id: 1,
+                name: "New York Cheese".to_owned(),
+            })]
+        );
+    }
+
+    #[tokio::test]
+    async fn test_load_many() {
+        use crate::{
+            entity::prelude::*, tests_cfg::*, DbBackend, IntoMockRow, LoaderTrait, MockDatabase,
+        };
+
+        let db = MockDatabase::new(DbBackend::Postgres)
+            .append_query_results(vec![vec![fruit::Model {
+                id: 1,
+                name: "Apple".to_owned(),
+                cake_id: Some(1),
+            }
+            .into_mock_row()]])
+            .into_connection();
+
+        let cakes = vec![
+            cake::Model {
+                id: 1,
+                name: "New York Cheese".to_owned(),
+            },
+            cake::Model {
+                id: 2,
+                name: "London Cheese".to_owned(),
+            },
+        ];
+
+        let fruits = cakes
+            .load_many(fruit::Entity::find(), &db)
+            .await
+            .expect("Should return something");
+
+        assert_eq!(
+            fruits,
+            vec![
+                vec![fruit::Model {
+                    id: 1,
+                    name: "Apple".to_owned(),
+                    cake_id: Some(1),
+                }],
+                vec![]
+            ]
+        );
+    }
+}

src/query/mod.rs

@@ -5,6 +5,7 @@ mod insert;
 mod join;
 #[cfg(feature = "with-json")]
 mod json;
+mod loader;
 mod select;
 mod traits;
 mod update;
@@ -17,6 +18,7 @@ pub use insert::*;
 pub use join::*;
 #[cfg(feature = "with-json")]
 pub use json::*;
+pub use loader::*;
 pub use select::*;
 pub use traits::*;
 pub use update::*;