Add confidence intervals to Forecast model

- add `.low80`, `.high80`, `.low95`, and `.high95` columns
- add check contraints for the confidence intervals
- rename the `.method` column into `.model` for consistency

migrations/env.py

@@ -21,7 +21,11 @@ log_config.fileConfig(context.config.config_file_name)
 
 def include_object(obj, _name, type_, _reflected, _compare_to):
     """Only include the clean schema into --autogenerate migrations."""
-    if type_ in {'table', 'column'} and obj.schema != umd_config.CLEAN_SCHEMA:
+    if (  # noqa:WPS337
+        type_ in {'table', 'column'}
+        and hasattr(obj, 'schema')  # noqa:WPS421 => fix for rare edge case
+        and obj.schema != umd_config.CLEAN_SCHEMA
+    ):
         return False
 
     return True

migrations/versions/rev_20210120_16_26711cd3f9b9_add_confidence_intervals_to_forecasts.py

@@ -0,0 +1,124 @@
+"""Add confidence intervals to forecasts.
+
+Revision: #26711cd3f9b9 at 2021-01-20 16:08:21
+Revises: #e40623e10405
+"""
+
+import os
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+from urban_meal_delivery import configuration
+
+
+revision = '26711cd3f9b9'
+down_revision = 'e40623e10405'
+branch_labels = None
+depends_on = None
+
+
+config = configuration.make_config('testing' if os.getenv('TESTING') else 'production')
+
+
+def upgrade():
+    """Upgrade to revision 26711cd3f9b9."""
+    op.alter_column(
+        'forecasts', 'method', new_column_name='model', schema=config.CLEAN_SCHEMA,
+    )
+    op.add_column(
+        'forecasts',
+        sa.Column('low80', postgresql.DOUBLE_PRECISION(), nullable=True),
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.add_column(
+        'forecasts',
+        sa.Column('high80', postgresql.DOUBLE_PRECISION(), nullable=True),
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.add_column(
+        'forecasts',
+        sa.Column('low95', postgresql.DOUBLE_PRECISION(), nullable=True),
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.add_column(
+        'forecasts',
+        sa.Column('high95', postgresql.DOUBLE_PRECISION(), nullable=True),
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.create_check_constraint(
+        op.f('ck_forecasts_on_ci_upper_and_lower_bounds'),
+        'forecasts',
+        """
+        NOT (
+            low80 IS NULL AND high80 IS NOT NULL
+            OR
+            low80 IS NOT NULL AND high80 IS NULL
+            OR
+            low95 IS NULL AND high95 IS NOT NULL
+            OR
+            low95 IS NOT NULL AND high95 IS NULL
+        )
+        """,
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.create_check_constraint(
+        op.f('prediction_must_be_within_ci'),
+        'forecasts',
+        """
+        NOT (
+            prediction < low80
+            OR
+            prediction < low95
+            OR
+            prediction > high80
+            OR
+            prediction > high95
+        )
+        """,
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.create_check_constraint(
+        op.f('ci_upper_bound_greater_than_lower_bound'),
+        'forecasts',
+        """
+        NOT (
+            low80 > high80
+            OR
+            low95 > high95
+        )
+        """,
+        schema=config.CLEAN_SCHEMA,
+    )
+    op.create_check_constraint(
+        op.f('ci95_must_be_wider_than_ci80'),
+        'forecasts',
+        """
+        NOT (
+            low80 < low95
+            OR
+            high80 > high95
+        )
+        """,
+        schema=config.CLEAN_SCHEMA,
+    )
+
+
+def downgrade():
+    """Downgrade to revision e40623e10405."""
+    op.alter_column(
+        'forecasts', 'model', new_column_name='method', schema=config.CLEAN_SCHEMA,
+    )
+    op.drop_column(
+        'forecasts', 'low80', schema=config.CLEAN_SCHEMA,
+    )
+    op.drop_column(
+        'forecasts', 'high80', schema=config.CLEAN_SCHEMA,
+    )
+    op.drop_column(
+        'forecasts', 'low95', schema=config.CLEAN_SCHEMA,
+    )
+    op.drop_column(
+        'forecasts', 'high95', schema=config.CLEAN_SCHEMA,
+    )