From ee504e7d9f8490a9759b6a3dcf121fd82011d602 Mon Sep 17 00:00:00 2001
From: Billy Chan <ccw.billy.123@gmail.com>
Date: Tue, 21 Sep 2021 12:01:07 +0800
Subject: [PATCH] `find_linked` join with table alias

---
 src/entity/link.rs  | 22 ++++++++++++++++++----
 src/entity/model.rs |  3 ++-
 src/query/helper.rs | 28 +++++++++++++++++++++++++---
 src/query/join.rs   |  7 ++++---
 4 files changed, 49 insertions(+), 11 deletions(-)

diff --git a/src/entity/link.rs b/src/entity/link.rs
index 97c9af1b..d0c262d7 100644
--- a/src/entity/link.rs
+++ b/src/entity/link.rs
@@ -1,5 +1,7 @@
-use crate::{EntityTrait, QuerySelect, RelationDef, Select};
-use sea_query::JoinType;
+use crate::{
+    join_tbl_on_condition, unpack_table_ref, EntityTrait, QuerySelect, RelationDef, Select,
+};
+use sea_query::{Alias, IntoIden, JoinType, SeaRc};
 
 pub type LinkDef = RelationDef;
 
@@ -12,8 +14,20 @@ pub trait Linked {
 
     fn find_linked(&self) -> Select<Self::ToEntity> {
         let mut select = Select::new();
-        for rel in self.link().into_iter().rev() {
-            select = select.join_rev(JoinType::InnerJoin, rel);
+        for (i, rel) in self.link().into_iter().rev().enumerate() {
+            let from_tbl = Alias::new(&format!("r{}", i)).into_iden();
+            let to_tbl = if i > 0 {
+                Alias::new(&format!("r{}", i - 1)).into_iden()
+            } else {
+                unpack_table_ref(&rel.to_tbl)
+            };
+
+            select.query().join_as(
+                JoinType::InnerJoin,
+                unpack_table_ref(&rel.from_tbl),
+                SeaRc::clone(&from_tbl),
+                join_tbl_on_condition(from_tbl, to_tbl, rel.from_col, rel.to_col),
+            );
         }
         select
     }
diff --git a/src/entity/model.rs b/src/entity/model.rs
index c6129ad7..ce4a3a4c 100644
--- a/src/entity/model.rs
+++ b/src/entity/model.rs
@@ -24,7 +24,8 @@ pub trait ModelTrait: Clone + Send + Debug {
     where
         L: Linked<FromEntity = Self::Entity>,
     {
-        l.find_linked().belongs_to(self)
+        let tbl_alias = &format!("r{}", l.link().len() - 1);
+        l.find_linked().belongs_to_tbl_alias(self, tbl_alias)
     }
 }
 
diff --git a/src/query/helper.rs b/src/query/helper.rs
index d93595f1..e6df3637 100644
--- a/src/query/helper.rs
+++ b/src/query/helper.rs
@@ -2,10 +2,11 @@ use crate::{
     ColumnTrait, EntityTrait, Identity, IntoIdentity, IntoSimpleExpr, Iterable, ModelTrait,
     PrimaryKeyToColumn, RelationDef,
 };
-pub use sea_query::{Condition, ConditionalStatement, DynIden, JoinType, Order, OrderedStatement};
 use sea_query::{
-    Expr, IntoCondition, LockType, SeaRc, SelectExpr, SelectStatement, SimpleExpr, TableRef,
+    Alias, Expr, Iden, IntoCondition, LockType, SeaRc, SelectExpr, SelectStatement, SimpleExpr,
+    TableRef,
 };
+pub use sea_query::{Condition, ConditionalStatement, DynIden, JoinType, Order, OrderedStatement};
 
 // LINT: when the column does not appear in tables selected from
 // LINT: when there is a group by clause, but some columns don't have aggregate functions
@@ -287,14 +288,35 @@ pub trait QueryFilter: Sized {
         }
         self
     }
+
+    fn belongs_to_tbl_alias<M>(mut self, model: &M, tbl_alias: &str) -> Self
+    where
+        M: ModelTrait,
+    {
+        for key in <M::Entity as EntityTrait>::PrimaryKey::iter() {
+            let col = key.into_column();
+            let expr = Expr::tbl(Alias::new(tbl_alias), col).eq(model.get(col));
+            self = self.filter(expr);
+        }
+        self
+    }
 }
 
-fn join_condition(rel: RelationDef) -> SimpleExpr {
+pub(crate) fn join_condition(rel: RelationDef) -> SimpleExpr {
     let from_tbl = unpack_table_ref(&rel.from_tbl);
     let to_tbl = unpack_table_ref(&rel.to_tbl);
     let owner_keys = rel.from_col;
     let foreign_keys = rel.to_col;
 
+    join_tbl_on_condition(from_tbl, to_tbl, owner_keys, foreign_keys)
+}
+
+pub(crate) fn join_tbl_on_condition(
+    from_tbl: SeaRc<dyn Iden>,
+    to_tbl: SeaRc<dyn Iden>,
+    owner_keys: Identity,
+    foreign_keys: Identity,
+) -> SimpleExpr {
     match (owner_keys, foreign_keys) {
         (Identity::Unary(o1), Identity::Unary(f1)) => {
             Expr::tbl(SeaRc::clone(&from_tbl), o1).equals(SeaRc::clone(&to_tbl), f1)
diff --git a/src/query/join.rs b/src/query/join.rs
index 19dc3160..e71b7027 100644
--- a/src/query/join.rs
+++ b/src/query/join.rs
@@ -76,6 +76,7 @@ where
 mod tests {
     use crate::tests_cfg::{cake, cake_filling, cake_filling_price, filling, fruit};
     use crate::{ColumnTrait, DbBackend, EntityTrait, ModelTrait, QueryFilter, QueryTrait};
+    use pretty_assertions::assert_eq;
 
     #[test]
     fn join_1() {
@@ -249,9 +250,9 @@ mod tests {
             [
                 r#"SELECT `filling`.`id`, `filling`.`name`"#,
                 r#"FROM `filling`"#,
-                r#"INNER JOIN `cake_filling` ON `cake_filling`.`filling_id` = `filling`.`id`"#,
-                r#"INNER JOIN `cake` ON `cake`.`id` = `cake_filling`.`cake_id`"#,
-                r#"WHERE `cake`.`id` = 12"#,
+                r#"INNER JOIN `cake_filling` AS `r0` ON `r0`.`filling_id` = `filling`.`id`"#,
+                r#"INNER JOIN `cake` AS `r1` ON `r1`.`id` = `r0`.`cake_id`"#,
+                r#"WHERE `r1`.`id` = 12"#,
             ]
             .join(" ")
         );