Migrate unit sizes to variant

db/migrate/20240819045115_migrate_unit_size_to_variants.rb

@@ -0,0 +1,21 @@
+class MigrateUnitSizeToVariants < ActiveRecord::Migration[7.0]
+   def up
+    # Copy variant_unit only if it's empty in the variant
+    ActiveRecord::Base.connection.execute(<<-SQL
+      UPDATE spree_variants
+      SET variant_unit = spree_products.variant_unit
+      FROM spree_products
+      WHERE spree_variants.product_id = spree_products.id
+      AND spree_variants.variant_unit IS NULL
+    SQL
+    )
+
+    ActiveRecord::Base.connection.execute(<<-SQL
+      UPDATE spree_variants
+      SET variant_unit_scale = spree_products.variant_unit_scale, variant_unit_name = spree_products.variant_unit_name
+      FROM spree_products
+      WHERE spree_variants.product_id = spree_products.id
+    SQL
+    )
+  end
+end