From 311cb8bd9154938f36eecb704f2e1d3f995e136e Mon Sep 17 00:00:00 2001
From: Billy Chan <ccw.billy.123@gmail.com>
Date: Mon, 6 May 2024 14:10:23 +0800
Subject: [PATCH] Postgres: allow foreign key column without unique constraint
 (#131)

* Postgres: allow foreign key column without unique constraint

* rename
---
 src/postgres/query/constraints/mod.rs | 16 ++++++++--
 tests/live/postgres/src/main.rs       | 44 +++++++++++++++++++++++++++
 2 files changed, 57 insertions(+), 3 deletions(-)

diff --git a/src/postgres/query/constraints/mod.rs b/src/postgres/query/constraints/mod.rs
index fdc53ad..1369762 100644
--- a/src/postgres/query/constraints/mod.rs
+++ b/src/postgres/query/constraints/mod.rs
@@ -188,9 +188,19 @@ impl SchemaQueryBuilder {
                             .equals((rcsq.clone(), RefC::ConstraintName)),
                     )
                     .add(
-                        // Only join when the referenced primary key position matches position_in_unique_constraint for the foreign key column
-                        Expr::col((Schema::KeyColumnUsage, Kcuf::PositionInUniqueConstraint))
-                            .equals((rcsq.clone(), Kcuf::OrdinalPosition)),
+                        Condition::any()
+                            .add(
+                                // Only join when the referenced primary key position matches position_in_unique_constraint for the foreign key column
+                                Expr::col((
+                                    Schema::KeyColumnUsage,
+                                    Kcuf::PositionInUniqueConstraint,
+                                ))
+                                .equals((rcsq.clone(), Kcuf::OrdinalPosition)),
+                            )
+                            .add(
+                                // Allow foreign key column without unique constraint
+                                Expr::col((rcsq.clone(), Kcuf::OrdinalPosition)).is_null(),
+                            ),
                     ),
             )
             .and_where(
diff --git a/tests/live/postgres/src/main.rs b/tests/live/postgres/src/main.rs
index 60889c6..4782cf7 100644
--- a/tests/live/postgres/src/main.rs
+++ b/tests/live/postgres/src/main.rs
@@ -55,6 +55,8 @@ async fn main() {
         create_parent_table(),
         create_child_table(),
         create_db_types_table(),
+        create_fkey_parent_table(),
+        create_fkey_child_table(),
     ];
 
     for tbl_create_stmt in tbl_create_stmts.iter() {
@@ -62,6 +64,15 @@ async fn main() {
         println!("{};", sql);
         println!();
         sqlx::query(&sql).execute(&mut *executor).await.unwrap();
+        if sql.starts_with(r#"CREATE TABLE "fkey_parent_table""#) {
+            let sql = Index::create()
+                .table(Alias::new("fkey_parent_table"))
+                .name("IDX_fkey_parent_table_unique_u")
+                .col(Alias::new("u"))
+                .unique()
+                .to_string(PostgresQueryBuilder);
+            sqlx::query(&sql).execute(&mut *executor).await.unwrap();
+        }
     }
 
     let schema_discovery = SchemaDiscovery::new(connection, "public");
@@ -456,3 +467,36 @@ fn create_db_types_table() -> TableCreateStatement {
         )
         .to_owned()
 }
+
+fn create_fkey_parent_table() -> TableCreateStatement {
+    Table::create()
+        .table(Alias::new("fkey_parent_table"))
+        .col(
+            ColumnDef::new(Alias::new("id"))
+                .integer()
+                .not_null()
+                .auto_increment(),
+        )
+        .col(ColumnDef::new(Alias::new("u")).integer().not_null())
+        .to_owned()
+}
+
+fn create_fkey_child_table() -> TableCreateStatement {
+    Table::create()
+        .table(Alias::new("fkey_child_table"))
+        .col(
+            ColumnDef::new(Alias::new("fk_u"))
+                .integer()
+                .not_null()
+                .auto_increment(),
+        )
+        .foreign_key(
+            ForeignKey::create()
+                .name("FK_tabl2_fkey_parent_table")
+                .from(Alias::new("fkey_child_table"), Alias::new("fk_u"))
+                .to(Alias::new("fkey_parent_table"), Alias::new("u"))
+                .on_delete(ForeignKeyAction::Cascade)
+                .on_update(ForeignKeyAction::Cascade),
+        )
+        .to_owned()
+}