67 lines
2.4 KiB
Python
67 lines
2.4 KiB
Python
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"""Provide the ORM's `Forecast` model."""
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import sqlalchemy as sa
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from sqlalchemy import orm
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from sqlalchemy.dialects import postgresql
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from urban_meal_delivery.db import meta
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class Forecast(meta.Base):
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"""A demand forecast for a `.pixel` and `.time_step` pair.
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This table is denormalized on purpose to keep things simple.
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"""
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__tablename__ = 'forecasts'
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# Columns
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id = sa.Column(sa.Integer, primary_key=True, autoincrement=True) # noqa:WPS125
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pixel_id = sa.Column(sa.Integer, nullable=False, index=True)
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start_at = sa.Column(sa.DateTime, nullable=False)
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time_step = sa.Column(sa.SmallInteger, nullable=False)
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training_horizon = sa.Column(sa.SmallInteger, nullable=False)
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method = sa.Column(sa.Unicode(length=20), nullable=False) # noqa:WPS432
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# Raw `.prediction`s are stored as `float`s (possibly negative).
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# The rounding is then done on the fly if required.
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prediction = sa.Column(postgresql.DOUBLE_PRECISION, nullable=False)
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# Constraints
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__table_args__ = (
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sa.ForeignKeyConstraint(
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['pixel_id'], ['pixels.id'], onupdate='RESTRICT', ondelete='RESTRICT',
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),
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sa.CheckConstraint(
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"""
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NOT (
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EXTRACT(HOUR FROM start_at) < 11
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OR
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EXTRACT(HOUR FROM start_at) > 22
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)
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""",
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name='start_at_must_be_within_operating_hours',
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),
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sa.CheckConstraint(
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'CAST(EXTRACT(MINUTES FROM start_at) AS INTEGER) % 15 = 0',
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name='start_at_minutes_must_be_quarters_of_the_hour',
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),
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sa.CheckConstraint(
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'EXTRACT(SECONDS FROM start_at) = 0', name='start_at_allows_no_seconds',
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),
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sa.CheckConstraint(
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'CAST(EXTRACT(MICROSECONDS FROM start_at) AS INTEGER) % 1000000 = 0',
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name='start_at_allows_no_microseconds',
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),
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sa.CheckConstraint('time_step > 0', name='time_step_must_be_positive'),
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sa.CheckConstraint(
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'training_horizon > 0', name='training_horizon_must_be_positive',
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),
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# There can be only one prediction per forecasting setting.
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sa.UniqueConstraint(
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'pixel_id', 'start_at', 'time_step', 'training_horizon', 'method',
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),
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)
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# Relationships
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pixel = orm.relationship('Pixel', back_populates='forecasts')
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