Add adjustment_total to spree_shipments

db/migrate/20210207151520_add_adjustment_total_to_shipment.rb

@@ -0,0 +1,31 @@
+class AddAdjustmentTotalToShipment < ActiveRecord::Migration
+  def up
+    add_column :spree_shipments, :adjustment_total, :decimal,
+               precision: 10, scale: 2, null: false, default: 0.0
+
+    populate_adjustment_totals
+  end
+
+  def down
+    remove_column :spree_shipments, :adjustment_total
+  end
+
+  def populate_adjustment_totals
+    # Populates the new `adjustment_total` field in the spree_shipments table. Sets the value
+    # to the shipment's (shipping fee) adjustment amount.
+
+    adjustment_totals_sql = <<-SQL
+      UPDATE spree_shipments
+      SET adjustment_total = shipping_adjustment.fee_amount
+      FROM (
+        SELECT spree_adjustments.source_id AS shipment_id, spree_adjustments.amount AS fee_amount
+        FROM spree_adjustments
+        WHERE spree_adjustments.source_type = 'Spree::Shipment'
+          AND spree_adjustments.amount <> 0
+      ) shipping_adjustment
+      WHERE spree_shipments.id = shipping_adjustment.shipment_id
+    SQL
+
+    ActiveRecord::Base.connection.execute(adjustment_totals_sql)
+  end
+end

db/schema.rb

@@ -780,6 +780,7 @@ ActiveRecord::Schema.define(version: 20210320003951) do
     t.integer  "stock_location_id"
     t.decimal  "included_tax_total",               precision: 10, scale: 2, default: "0.0", null: false
     t.decimal  "additional_tax_total",             precision: 10, scale: 2, default: "0.0", null: false
+    t.decimal  "adjustment_total",                 precision: 10, scale: 2, default: "0.0", null: false
     t.index ["number"], name: "index_shipments_on_number", using: :btree
     t.index ["order_id"], name: "index_spree_shipments_on_order_id", unique: true, using: :btree
   end