Add differing capacities (#69)

* add support for differing capacities

* format and lint

* explicitely specify new column name

* add back capacity_kw column

* add trigger to set default value of inverter_capacity_kw to capacity_kw

alembic/versions/8384de6b7c50_add_support_for_differing_inverter_and_.py

@@ -0,0 +1,58 @@
+"""Add support for differing inverter and module capacities
+
+Revision ID: 8384de6b7c50
+Revises: aeea08bcfc42
+Create Date: 2023-04-08 12:26:23.042938
+
+"""
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.sql import table, column
+
+# revision identifiers, used by Alembic.
+revision = '8384de6b7c50'
+down_revision = 'aeea08bcfc42'
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column('sites', sa.Column('module_capacity_kw', sa.Float(), nullable=True, comment='The PV module nameplate capacity of the site'))
+    op.add_column('sites', sa.Column('inverter_capacity_kw', sa.Float(), nullable=True, comment='The PV module nameplate capacity of the site'))
+
+    op.execute("UPDATE sites SET inverter_capacity_kw=capacity_kw")
+
+    # Create a trigger function to set inverter_capacity_kw to capacity_kw
+    op.execute("""
+        CREATE OR REPLACE FUNCTION set_default_inverter_capacity_kw()
+        RETURNS TRIGGER AS $$
+        BEGIN
+            NEW.inverter_capacity_kw := NEW.capacity_kw;
+            RETURN NEW;
+        END;
+        $$ LANGUAGE plpgsql;
+    """)
+
+    # Create trigger on sites table, for when inverter_capacity_kw is NULL
+    op.execute("""
+        CREATE TRIGGER set_default_inverter_capacity_kw_trigger
+        BEFORE INSERT ON sites
+        FOR EACH ROW
+        WHEN (NEW.inverter_capacity_kw IS NULL)
+        EXECUTE FUNCTION set_default_inverter_capacity_kw();
+    """)
+
+def downgrade() -> None:
+    # Drop the trigger from the 'sites' table
+    op.execute("""
+        DROP TRIGGER set_default_inverter_capacity_kw_trigger ON sites;
+    """)
+
+    # Drop the trigger function
+    op.execute("""
+        DROP FUNCTION set_default_inverter_capacity_kw;
+    """)
+
+    op.drop_column('sites', 'module_capacity_kw')
+    op.drop_column('sites', 'inverter_capacity_kw')
+