import old data

migration/src/lib.rs

@@ -53,6 +53,7 @@ mod m20260625_000001_add_avatar_to_users;
 mod m20260627_000001_order_residence_address;
 mod m20260627_000002_payment_settings;
 mod m20260627_000003_account_cart_items;
+mod m20260729_000001_add_legacy_id;
 pub struct Migrator;
 
 #[async_trait::async_trait]
@@ -110,6 +111,7 @@ impl MigratorTrait for Migrator {
             Box::new(m20260627_000001_order_residence_address::Migration),
             Box::new(m20260627_000002_payment_settings::Migration),
             Box::new(m20260627_000003_account_cart_items::Migration),
+            Box::new(m20260729_000001_add_legacy_id::Migration),
             // inject-above (do not remove this comment)
         ]
     }

migration/src/m20260729_000001_add_legacy_id.rs

@@ -0,0 +1,49 @@
+//! `legacy_id` — the row's id in the old PrestaShop e-shop
+//! (<http://e-shop.kompress.sk>), recorded during the catalog import.
+//!
+//! Its only job is to make the import repeatable: the task looks a row up by
+//! `legacy_id` to decide "already imported, skip" instead of inserting a second
+//! copy. SKU cannot serve that purpose — the old shop reuses codes both across
+//! products and across sizes of one product (e.g. `2181` on two sizes of the
+//! same item), so it identifies nothing.
+//!
+//! NULL for everything created in this shop; only imported rows carry a value.
+//! The uniqueness is enforced by a partial unique index rather than in Rust
+//! because it is exactly the guarantee the import relies on to stay idempotent,
+//! and it has to hold even if two imports were ever run concurrently.
+
+use loco_rs::schema::*;
+use sea_orm_migration::prelude::*;
+
+#[derive(DeriveMigrationName)]
+pub struct Migration;
+
+const TABLES: [&str; 3] = ["categories", "products", "product_variants"];
+
+#[async_trait::async_trait]
+impl MigrationTrait for Migration {
+    async fn up(&self, m: &SchemaManager) -> Result<(), DbErr> {
+        for table in TABLES {
+            add_column(m, table, "legacy_id", ColType::IntegerNull).await?;
+            // Partial index: many rows legitimately have no legacy id, and
+            // NULLs must not collide with each other.
+            m.get_connection()
+                .execute_unprepared(&format!(
+                    "CREATE UNIQUE INDEX idx_{table}_legacy_id
+                       ON {table} (legacy_id) WHERE legacy_id IS NOT NULL;"
+                ))
+                .await?;
+        }
+        Ok(())
+    }
+
+    async fn down(&self, m: &SchemaManager) -> Result<(), DbErr> {
+        for table in TABLES {
+            m.get_connection()
+                .execute_unprepared(&format!("DROP INDEX IF EXISTS idx_{table}_legacy_id;"))
+                .await?;
+            remove_column(m, table, "legacy_id").await?;
+        }
+        Ok(())
+    }
+}