"""A router's latency may be absent

Latency is now each scrape's own percentile (#5741), and a scrape in which a
router answered nothing has none: those rows carry NULL rather than a
made-up 0 or the old lifetime figure.

Revision ID: traefik_007_latency_nullable
Revises: traefik_006_status_codes
Create Date: 2026-10-14
"""
from typing import Sequence, Union
from alembic import op

revision: str = "traefik_007_latency_nullable"
down_revision: Union[str, None] = "traefik_006_status_codes"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None

_COLUMNS = ("latency_p50_ms", "latency_p95_ms", "latency_p99_ms")


def upgrade() -> None:
    for column in _COLUMNS:
        op.alter_column("traefik_metrics", column, nullable=True)


def downgrade() -> None:
    for column in _COLUMNS:
        op.execute(f"UPDATE traefik_metrics SET {column} = 0 WHERE {column} IS NULL")
        op.alter_column("traefik_metrics", column, nullable=False)