59 lines
2.5 KiB
Python
59 lines
2.5 KiB
Python
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"""decouple dsmr_reading from the telegram id
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The DSMR Reader's own ``id`` field is auto-incrementing but is known to overflow
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and require a manual reset to zero (a long-standing DSMR firmware quirk). If we
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keep a UNIQUE constraint on ``source_id`` (the telegram id) and use it for
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idempotency, an overflow/reset would make legitimately-new telegrams collide with
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old ids and be silently dropped as "duplicates" — data loss.
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This migration removes that coupling:
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- Drops the UNIQUE constraint on ``source_id`` (the column is kept as a plain,
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nullable reference value; it is no longer relied upon for uniqueness/dedup).
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- Makes ``recorded_at`` (the telegram timestamp) UNIQUE instead — a single P1
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meter emits one telegram per timestamp, so this is a robust, telegram-id-
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independent idempotency key. The table's own autoincrement ``id`` PK remains
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the stable internal identity.
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Revision ID: 20260624_12_dsmr_decouple_telegram_id
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Revises: 20260623_11_energy_tables
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Create Date: 2026-06-24 00:00:00.000000
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"""
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from typing import Sequence, Union
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from alembic import op
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revision: str = "20260624_12_dsmr_decouple_telegram_id"
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down_revision: Union[str, None] = "20260623_11_energy_tables"
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branch_labels: Union[str, Sequence[str], None] = None
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depends_on: Union[str, Sequence[str], None] = None
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def upgrade() -> None:
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# SQLite cannot ALTER away a constraint in place, so recreate the table via
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# Alembic's batch mode. The table is recreated and rows are copied; existing
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# data (if any) is preserved. recorded_at must be unique for this to succeed
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# — a single meter never emits two telegrams at the exact same timestamp.
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with op.batch_alter_table("dsmr_reading", schema=None) as batch_op:
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# Old non-unique index on recorded_at is replaced by the unique constraint.
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batch_op.drop_index("ix_dsmr_reading_recorded_at")
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# Telegram id is no longer a uniqueness/idempotency key.
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batch_op.drop_constraint("uq_dsmr_reading_source_id", type_="unique")
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# Timestamp becomes the telegram-id-independent dedup key.
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batch_op.create_unique_constraint(
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"uq_dsmr_reading_recorded_at", ["recorded_at"]
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)
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def downgrade() -> None:
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with op.batch_alter_table("dsmr_reading", schema=None) as batch_op:
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batch_op.drop_constraint("uq_dsmr_reading_recorded_at", type_="unique")
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batch_op.create_unique_constraint(
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"uq_dsmr_reading_source_id", ["source_id"]
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)
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batch_op.create_index(
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"ix_dsmr_reading_recorded_at", ["recorded_at"], unique=False
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)
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